b. Chemical properties
1. Metals form their oxides when burn with oxygen. But gold (Au) and platinum (Pt) do
not form their oxides.
4Na + O2 burn 2Na2O
(Sodium oxide)
4K + O2 burn 2K2 O
(Potassium oxide)
2Ca + O2 burn 2CaO
(Calcium oxide)
2. Non-metals form their oxides when burn with oxygen.
2H2 + O2 burn 2H2O (water)
C + O2 burn CO2 (Carbon dioxide)
S + O2 SO2 (Sulphur dioxide)
3. All hydrocarbons burn with oxygen to produce carbon dioxide, water and energy.
CH4 + 2O2 heat CO2 + 2H2O + energy
C2H4 + 3O2 heat 2CO2 + H2O + energy
4. In the process of digestion of food, the food like carbohydrates is first changed into
glucose and is then oxidized by oxygen and energy is liberated.
C6 H12 O6 + 6O2 6CO2 + 6H2O + energy
Uses of Oxygen gas
1. Energy is released due to reaction between oxygen and carbohydrate. This energy is
used to conduct life process.
2. It is used for welding purpose with the help of oxy-acetylene flame or oxy-hydrogen
flame.
3. Patient who suffer from breathing trouble or Pneumonia are given oxygen to activate
their breathing in hospitals.
4. People working at deep mines also use oxygen cylinders if there is less oxygen in the
air.
5. It is used for manufacturing of very important industrial chemicals like sulphuric
acid, nitric acid, etc.
6. Liquid oxygen is used in rockets for burning fuel.
GREEN Science (Chemistry) Book-9 201
3. Nitrogen Gas
Generally, nitrogen gas does not react with other elements or compounds. Comparably,
it is an inert gas. But Nitrogen gas is an essential constituent of animal and plant life. It
is found in the protein, enzymes, R.N.A, D.N.A., etc. of animals and plants. It constitutes
about 79% (by volume) of atmosphere. In combined state, it is found in the form of
ammonia, ammonium salts, etc.
Daniel Rutherford discovered Nitrogen in 1772. In 1790, Chaptal named it as "Nitrogen."
Some facts about Nitrogen
Symbol Molecular Atomic number Atomic weight Electronic
N formula 7 14 configuration
N2 1s², 2s² 2p³
Methods of Preparation of Nitrogen Gas
Nitrogen gas can be prepared by various methods such as by burning phosphorus in air,
from liquid air, by heating the mixture of sodium nitrate and ammonium chloride, etc.
In this chapter, we will discuss the laboratory preparation and industrial manufacture of
nitrogen gas.
a. Laboratory preparation of Nitrogen gas
The mixture of sodium nitrite (NaNO2) and ammonium chloride (NH4Cl) is heated
to prepare nitrogen gas in the laboratory.
NaNO2 + NH4Cl burn N2 + NaCl + H2O
Thistle funnel Delivery tube
Stand
Fig. Round bottom Tripod stand Nitrogen gas
flask Burner
Gas gar
Ammonium Laboratory preparation of Nitrogen gas Water
chloride +
Water trough
Sodium nitrite Beehive shelf
(NH4Cl+NaNO2)
11.5
Method
The mixture of 5gm of sodium nitrite and 4 gm of ammonium chloride mixed in a clean
round bottom flask. Then 50ml of water is added in that mixture to make the solution of
202 GREEN Science (Chemistry) Book-9
sodium nitrite and ammonium chloride. The rest of the apparatus is set up as shown in
the figure. On heating the solution gently, nitrogen gas is evolved which is collected in the
gas jar by downward displacement of water.
Precautions
1. The solution should be prepared before heating as the solid ammonium chloride is
volatile even at low temperature.
2. The apparatus should be air tight.
3. The solution should be heated slowly.
Test of nitrogen gas
When a burning magnesium ribbon is inserted into the gas jar of nitrogen, it burns in
nitrogen gas forming yellowish powder. If there is smell of ammonia when few drops of
water are added, it proves the gas collected in the gas jar is nitrogen.
b. Manufacture of Nitrogen Gas
From liquid Air
The air can be changed into liquid state with a high pressure after cooling. In liquid air
there is mostly nitrogen and then oxygen. The boiling point of liquid nitrogen is (– 196°C)
and that of liquid oxygen is (– 183°C).
So, when liquid air is heated, nitrogen is evolved in first section and oxygen still remains in
liquid state. This oxygen in liquid state is heated at – 183°C and liquid oxygen is changed
into gas. The oxygen and nitrogen gases evolved are collected in separate cylinders. In this
way, manufacture of oxygen is possible from liquid air. This method helps to manufacture
both oxygen and nitrogen gases.
Properties of Nitrogen Gas
a. Physical Properties
i. It is a colourless, odourless and tasteless gas.
ii. It is slightly lighter than air.
iii. It is slightly soluble in water.
iv. It is neutral . It does not have any effect on indicator.
v. It is non-combustible gas and does not support combustion.
vi. It can be liquefied at – 196°C and solidified at – 210° C.
b. Chemical Properties
1. At a very high temperature (2000° C – 3000°C) of nitrogen and oxygen combine to
form nitric oxide.
N2 + O2 electric arc 2NO (Nitric oxide)
GREEN Science (Chemistry) Book-9 203
2. When the mixture of nitrogen and hydrogen is heated with catalyst (Fe/Mo) at 450° C
and 500 Atm. pressure, ammonia is formed.
N2 + 3H2 455°C ∼ 500Atm 2NH3 (ammonia gas)
3. Some of the active metals like magnesium, aluminium, calcium, etc. continue to burn
in atmosphere of nitrogen forming their respective nitrides.
3Mg + N2 burn Mg3N2 Do You Know
(magnesium nitride)
3Ca + N2 burn Ca3N2 Nitrogen gas creates pressure inside the
(calcium nitride) bulb which prevents the filament from
burning. So, it is filled inside electric bulb.
2Al + N2 burn 2AlN (Aluminum nitride)
Uses of Nitrogen Gas
1. It is used for manufacturing of ammonia, nitric acid, cyanides, nitrides, etc.
2. Being inactive, it is used in filling electric bulbs and high temperature thermometers.
3. The temperature of liquid nitrogen is – 196.5°C. So, it is used as refrigerant.
4. It is used in filling air space of compounds to retain their flavour and colour better.
Key Concepts
1. Water is formed when hydrogen burns in presence of oxygen.
2. Hydrogen gas is used to make vegetable ghee which is obtained as a result of
chemical reaction between vegetable oil and hydrogen. This process is called
hydrogenation.
3. Hydrogen gas burns with 'pop' sound.
4. Manufacture of oxygen is possible from liquid air.
5. Oxygen gas is used in artificial respiration, while diving in deep oceans, while
climbing high peaks.
6. Oxy-acetylen flame and oxy-hydrogen flame are used for cutting metals and
welding purpose.
7. Liquid oxygen is used as fuel in missile and rocket.
8. Nitrogen gas is prepared by heating the mixture of sodium nitrite and ammonium
chloride.
9. Nitrogen gas is used in the production of ammonia, nitric acid and nitroglycerin.
10. Nitrogen gas is used in electric bulbs as it does not react with oxygen and prevents
burning.
204 GREEN Science (Chemistry) Book-9
Sequential General Exercise 1
1. Choose the best answer from the given alternatives.
a. Which of the following gas is completely insoluble in water?
Nitrogen Hydrogen
Ammonia Oxygen
b. What is the process of making vegetable ghee from vegetable oil?
hydrogenation reduction
oxidation carbonation
c. Which of the following is heated for the production of oxygen gas
KClO3 CaCO3
H2O2 Fe2O3
d. Which compound is formed when magnesium burns with nitrogen?
Magnesium nitrate Magnesium nitrite
Magnesium oxide Magnesium nitride
2. Answer the following questions.
a. Describe the method of laboratory preparation of hydrogen with a labelled
diagram.
b. What are the precautions during laboratory preparation of hydrogen gas?
c. What happens when hydrogen react with water? Write with chemical equation.
d. What is hydrogenation? Write its importance in our daily life.
e. Write any four uses of hydrogen gas.
f. Write with balanced chemical equation when hydrogen reacts with .
i. Sodium ii. Oxygen iii. Nitrogen iv. Ferric oxide
g. Write any two physical and two chemical properties of hydrogen gas.
h. Describe the method of laboratory preparation of oxygen gas by using heat. Also,
draw a well labelled figure.
i. Describe the method of laboratory preparation of oxygen gas without using heat.
Also, draw a well labelled figure.
GREEN Science (Chemistry) Book-9 205
j. Describe in brief the industrial preparation of oxygen gas.
k. Write any four physical properties of oxygen gas.
l. How can you prove that the gas inside the jar is oxygen gas?
m. What happens when metals and non-metals burn with oxygen? Write with
example.
n. Write any four main uses of oxygen gas.
o. Describe with a neat and well labelled diagram of the laboratory preparation of
nitrogen gas.
p. How is nitrogen gas tested? Write.
q. Write the balanced chemical equation when oxygen gas reacts with nitrogen.
r. What are the physical properties of nitrogen gas? Write any four uses of nitrogen
gas.
s. How is nitrogen gas prepared in industries? Describe in brief.
3. Complete and balance the given chemical equations.
a. 2H2 + .............. 2H2O
b. CH4 .............. CO + H2
c. Na + H2 burn ................
d. .................. heat KCl + 3O2
e. H2 O2 MnO2 H2 O + ..................
f. ............... + O2 burn CO2 + 2H2O + energy
g. C6H12 O6 + O2 biocatalyst ............. + ........... energy
h. ............. burn H2 + O2
i. K + O2 ..................
j. NaNO2 + ............. heat NaCl + N2 + ..............
k. 3Mg + N2 burn ........................
l. S + O2 ......................
206 GREEN Science (Chemistry) Book-9
Grid-based Exercise 2
Group ‘A’ (Knowledge Type Questions) (1 Mark Each)
1. What is air?
2. What is the percentage of nitrogen and oxygen in air?
3. Why is hydrogen called the simplest element?
4. Write any two physical properties of hydrogen gas.
5. What is hydrogenation ?
6. Name the scientist who discovered hydrogen gas.
7. What is a catalyst?
8. Write down the melting point and boiling point of hydrogen.
9. Write any two physical properties of oxygen gas.
10. Write down any two physical properties of nitrogen.
11. Name the scientist who discovered oxygen gas.
12. Write down the molecular formula of niter and salt petre.
For Group ’B’ (Understanding Type Questions) (2 Marks Each)
13. How is hydrogen gas tested? Why is hydrogen filled in balloons? Write.
14. Hydrogen gas is not found freely in nature, why? Why do active metals displace
hydrogen from acids ?
15. Why is nitrogen gas called azota ? Why do mountain climbers take oxygen cylinder?
16. Nitrogen gas is filled inside the electric bulb. Why? Why is impure zinc used for
preparing hydrogen gas in laboratory?
17. Nitrogen gas is filled in the fuel tanks of aircrafts. Why? Why is hydrogen gas used
for welding ?
18. While preparing oxygen gas, the delivery tube is separated from water trough before
heating is stopped. Why?
19. Nitrogen gas is important for green plants. Why?
For Group ‘C’ (Application Type Questions) (3 Marks Each)
20. How is urea prepared by using hydrogen gas? Write. Write any three uses of nitrogen
gas.
21. How is hydrogen gas manufactured in industries? Write.
22. Write any three uses of hydrogen.
23. How is nitrogen extracted from air ? Describe in brief.
24. Write down any three uses of oxygen gas.
25. How is chemical fertilizer prepared from nitrogen ? Write in brief. What is oxyhydrogen
flame? Why is it used?
GREEN Science (Chemistry) Book-9 207
For Group ‘D’ (Higher Abilities Type Questions) (4 Marks Each)
26. Describe the method of laboratory preparation of hydrogen gas with a labelled
diagram.
27. Describe the method of laboratory preparation of oxygen gas by using heat. Also,
draw a well labelled figure.
28. Answer the following questions on the basis of the given figure:
i. Which gas is Hard glass test tube
being collected in Potassium chlorate Cork Oxygen gas
Delivery tube Gas jar
+ Stand
Manganese dioxide Water trough
the gas jar ? Beehive shelf
ii. What will happen
if this gas is Bunsen burner
heated with
phosphorus ?
Write with chemical equation.
iii. Describe the role of Manganese dioxide in the above process.
29. Answer the following questions on the basis of given figure.
i. Which gas is being collected Hydrogen peroxide Delivery tube
in the gas jar ? Stopper Beehive shelf
ii. Write down the role of Cork Oxygen gas
MnO2 in this process, Conical flask Gas jar
Mixture of H2O2 + MnO2
iii. Write down the balanced Water
chemical equation of the Water trough
preparation of this gas.
30. Study the given figure and answer the following questions:
i. Which gas is being Thistle funnel Delivery tube
collected in the gas jar ? Stand
Tripod stand Nitrogen gas
ii. Write down the balanced Round bottom Burner
chemical equation of the flask Gas gar
reaction that takes place in Water
the above process, Ammonium
chloride + Water trough
iii. What will happen when Beehive shelf
this gas is heated with Sodium nitrite
oxygen? Write with (NH4Cl+NaNO2)
chemical equation.
208 GREEN Science (Chemistry) Book-9
UNIT Metal
12
Weighting Distribution Theory : 5 Practical: 1
Before You Begin
A variety of substances are found around us. These substances are
formed by different types of matter. For example, gold, copper,
wood, plastic, paper, stone, etc. These substances may be element or
compound. Elements are the pure substances made up of only one
type of atoms. Compounds are the substances formed by combination
of two or more elements in a fixed proportion by weight. Elements
are divided into metals, non-metals and metalloids on the basis of
their characteristics. Metals are electropositive elements which can
conduct heat and electricity. Gold, copper, silver, iron, aluminium,
zinc, magnesium, sodium, mercury, etc. are some examples of metals.
In this unit, we will study about metals, differences between metals
and non-metals and role of some metals in human body in brief.
Learning Objectives Syllabus
After completing the study of this unit, students will be able to: • Introduction to metals
i. introduce metals and non-metals with examples.
• Physical and chemical
ii. differentiate between metals and non-metals. properties of metals
iii. explain the properties of metals and non-metals. • Non-metals and alloys
iv. introduce alloys and metalloids. • Metalloids
v. explain the role of metals in living beings [zinc as • Role of metals in organisms
enzyme, significance of sodium and potassium ions,
negative impacts of mercury (Hg) and lead (Pb) in • Harmful effects of mercury
human body]. and lead
Glossary: A dictionary of scientific/technical terms
metals : the electropositive elements which can conduct heat and electricity
metalloids : the substances having properties of both metals and non-metals
lustre : the shining quality of a surface
alloy : a homogeneous mixture of two or more metals or metals and non-metals
lustrous : having shiny nature
malleability : the property of a substance due to which it can be beaten into a thin sheet
ductility : the property of a substance due to which it can be drawn into a wire
conductivity : the property of a substance due to which it can conduct heat and electricity
GREEN Science (Chemistry) Book-9 209
Metals
Metals are those substances which are hard, malleable, ductile and good conductors of
heat and electricity. For example, iron, copper, aluminium, gold, silver, etc. They are
shiny (lustrous) and produce tinkling sound when hammered. All solids exist in solid
state except mercury. We use metals like iron, aluminium, copper, silver, gold, etc. in our
daily life. Metals are used for making cooking utensils, construction materials, vehicles,
ornaments, furniture, electric wires, weapons, etc.
Fig.
12.1
Cooking utensils made of Cooking utensils made of Cooking utensils made of
iron copper aluminium
Properties of Metals
1. Most metals are found in solid state except mercury.
2. Most metals are malleable, i.e. they can be beaten into thin sheets.
3. Most metals are ductile, i.e. a thin and long wire can be made from metals.
4. Metals are lustrous, i.e. having shiny nature.
5. Metals are good conductor of heat and electricity.
6. They produce tinkling sound on hitting.
7. Most metals are hard except lithium, sodium and potassium.
Activity 1
Take a piece of wood, a piece of copper, a piece of coal, sulphur, an iron nail, etc.
Press each of them one by one hard or soft. Try to break them and write down the
result in the table.
Substances Hard Soft Can be Cannot be
1. Iron nail √× broken broken
× √
2. Coal
3. A piece of copper
4. Sulphur
5. Wood
210 GREEN Science (Chemistry) Book-9
Activity 2
Take a sheet of copper, gold ornament, coal, sulphur, paper, a sheet of zinc, etc.
Observe whether they are shiny or not.
Fill in the table after your observation.
Substances Shines Does not shine
1. A sheet of copper √ √
2. Coal
3.
4.
5.
Activity 3
Make a list of substances that can be used to make a long wire.
The property of a metal be virtue of which it can be drawn into a long wire is called
ductility. Most metals are ductile because they can be drawn into long wires.
Metals can be stretched slowly to make wire. When metals are stretched the positively
charged ions and electrons in required amount are stretched slowly. As a result, the metal
changes into a wire. This property of metals in called ductility.
The interatomic force of attraction is more in metals. So, they are hard and strong. As
metals are hard and strong, they have high melting point and boiling point.
The melting point and boiling point of some common metals is given below.
S.N. Metals Melting point Boiling point
1. Potassium (K) 63.5°C 759°C
2. Sodium (Na) 97.79°C 882.94°C
3. Magnesium (Mg) 650°C 1107°C
4. Aluminium (Al) 660°C 2467°C
5. Iron (Fe) 1535°C 2750°C
6. Copper (Cu) 1083°C 2567°C
Above table shows that the melting point of potassium and sodium is very less as
compared to that of other metals.
Chemical Properties of Metals
1. Metals react with oxygen and produce corresponding oxides.
When metals burn in oxygen, they form metal oxides.
Mg + O2 burn 2MgO (Magnesium oxide)
GREEN Science (Chemistry) Book-9 211
Al + O2 Al2O3 (Aluminium oxide)
Ca + O2 2CaO (Calcium oxide)
Cu + O2 2CuO (Copper oxide)
2. Active metals react with acids and form corresponding salt and hydrogen gas.
Mg + 2HCl MgCl2 + H2
2Fe + 6HCl 2FeCl3 + 3H2
2Al + 6HCl 2AlCl3 + 3H2
Mg + H2SO4 MgSO4 + H2
Zn + H2SO4 ZnSO4 + H2
Zn + 2HCl ZnCl2 + H2
Ca + H2SO4 CaSO4 + H2
3. Some active metals like Sodium, Potassium, Calcium, etc. react with hydrogen and
form unstable hydrides. For example:
Na + H2 burn 2NaH
K + H2 burn 2KH
Ca + H2 burn CaH2
Activity 4
Take a beaker and make 50 ml of concentrated solution of copper sulphate.
Take another beaker and make 50 ml of concentrated solution of ferrous sulphate.
Take an iron nail, tie it with a thread and immerse it in the solution of copper
sulphate.
Take a piece of copper, tie it with a thread and immerse it in the solution of ferrous
sulphate.
Observe the iron nail and piece of copper after five minutes.
What do your observe?
Write down the conclusion of this activity.
Non-Metals
Non-metals are those substances which are generally soft, non-malleable, non-ductile and
bad conductors of heat and electricity. They exist in all three states, viz. solid, liquid and
gas. Carbon, iodine, sulphur, phosphorus, chlorine, etc. are examples of non-metals.
We use many non-metals in our daily life. Non-metals are used in construction works, to
make containers, utensils, medicines, etc.
212 GREEN Science (Chemistry) Book-9
Fig.
12.2 Phosphorus Sulphur
Carbon
Properties of Non-metals
1. Non-metals are found in all three states, i.e. Do You Know
solid, liquid and gas.
All non-metals are bad conductor of
2. They are non-malleable. heat and electricity except graphite.
3. They are non-ductile.
4. They are non-lustrous except iodine. Metals are sonorous and non-metals
are non-sonorous.
5. They are non-conductors of heat and
electricity except graphite.
6. They do not produce tinkling sound on hitting.
7. Non-metals are generally soft.
Activity 5
Collect various materials found at your home like metal wires, coins,
spoon, brick, pencil, lead of pencil, plastics, iron nail, etc.
Study the characteristics of these substances like malleability, ductility,
conductivity, etc.
Classify them in terms of metal and non-metals.
Differences between Metals and Non-metals
Metals Non-metals
1. Metals are good conductors of heat 1. Non-metals are bad conductors of heat
and electricity. and electricity.
2. They are malleable. 2. They are non-malleable.
3. They are ductile. 3. They are non-ductile.
4. They are lustrous. 4. They are non-lustrous.
5. Most metals are hard. 5. Most metals are soft.
6. They are sonorous. 6. They are non-sonorous.
GREEN Science (Chemistry) Book-9 213
Experiment: 1
To demonstrate that metals are good conductor and non-metals are bad conductor of
heat.
Requirements : Bunsen burner, spirit lamp or a candle, match box, an iron rod, a wooden
stick
Procedure
• Take an iron rod and a wooden stick of the same shape and size.
• Heat the one end of iron rod with a burner/ spirit lamp/ candle for a few minutes and
catch the other end of the rod. Repeat the same process for wooden stick.
Observation : The outer end of the iron rod is felt hot when heated for a few minutes
but the outer end of wooden stick is not felt hot. Iron is good conductor
of heat. So when one end of iron rod is heated for a while its another
end is felt hot due to conduction of heat. But wood is bad conductor of
heat, it does not conduct heat from one end to another. So another end
of wooden stick is not felt hot.
Wooden stick Iron rod
Fig.
12.3 From this experiment, it can be concluded that metals are good conductor
Conclusion : and non-metals are bad conductor of heat.
Experiment: 2
To demonstrate that metals are good conductor and non-metals are bad conductor of
electricity.
Requirements : Battery, electric bulb, copper wire, coin, a piece of wood, rubber, a piece
of plastic, a piece of blade
Procedure
• Take a battery, an electric bulb and pieces of copper wire
• Assemble an open circuit as shown in the figure.
• Leave the gap PQ in the circuit.
• Place a coin, to connect the ends of wire PQ. What do you observe? Does the bulb
glow? Why?
214 GREEN Science (Chemistry) Book-9
• Remove the coin and repeat this activity by using a piece of wood, rubber, a piece of
plastic, a piece of blade, etc. one by one.
Bulb glows Bulb does not glow
PQ PQ
Coin (Conductor)
Wood (insulator)
Fig.
12.4 Battery
Observation :
When the circuit is completed by using metal objects (coin, piece of
Conclusion : copper wire, coin, iron, etc.), the bulb glows but the bulb does not glow
when circuit is completed with non-metals (wood, rubber, plastic,
etc.). It shows that metals are good conductors and non-metals are bad
conductors of electricity.
From this experiment, it can be concluded that metals are good conductor
and non-metals are bad conductor of electricity.
Experiment: 3
To demonstrate that metals are malleable and non-metals are non-malleable.
Requirements : Hammer, a thick copper wire, a thick iron wire, a piece of brick, a piece
of stone
Procedure
• Take a thick wire of iron and hit it several times with a hammer. Now, take a piece of
brick and hammer it. What do you observe?
• Repeat this activity with a thick wire of copper and a piece of stone. What do you
observe?
Observation : Copper wire and iron wire become flat on hammering but they do not
break down into pieces. It shows that metals are malleable. On other
hand, brick and stone break down into many small pieces on hammering.
It shows that non-metals are non-malleable.
Conclusion : From this experiment, it can be concluded that metals are malleable and
non-metals are non-malleable.
GREEN Science (Chemistry) Book-9 215
Experiment: 4
To demonstrate that metals are lustrous and non-metals are non-lustrous.
Requirements : steel plate, wooden board, cardboard paper,
Procedure
• Take a steel plate and reflect the sunlight using the plate.
• Repeat this activity with wooden board and cardboard paper one by one. What do
you observe? Which object appears shiny? Why?
Observation : Steel plate appears shiny and reflects light. But the wooden board and
cardboard paper do not reflect light. It shows that steel plate is lustrous
but wooden board and cardboard are non-lustrous.
Experiment: 5
To demonstrate that metals are sonorous and non-metals are non-sonorous.
Requirements : A hammer, a bell, steel plate, wooden block, brick
Procedure
• Take a hammer and hit a bell, steel plate, wooden block, brick one by one.
• Observe which object produces tinkling sound while hammering. Is there any
difference between the sound produced by metals and non-metals when they are
hammered? What do you observe?
Observation : The metal articles (bell, steel plate) produce tinkling sound and non-
metals (wooden block, brick) do not produce tinkling sound on
hammering. It shows that metals are sonorous and non-metals are non-
sonorous.
Conclusion From this experiment, it can be concluded that metals are sonorous and non-
metals are non-sonorous.
Alloy
An alloy is the homogeneous mixture of two more metals or metals and non-metals. Alloys
are formed by mixing molten mass of two or more metals or metals and non-metals and
cooling the product. The alloy which is formed by mixing a metal and mercury is called
amalgam. Examples:
Alloy Components
1. Brass
2. Stainless steel Copper (70%) and Zinc (30%)
Iron (89.4%), Chromium (10%), Manganese (0.35%) and
carbon (0.25%)
216 GREEN Science (Chemistry) Book-9
3. Bronze Copper (88%) and Tin (12%)
4. Artificial gold Copper (90%) and Aluminium (10%)
5. Bell metal Copper (80%) and Tin (20%)
Fig.
12.5 Rold gold Stainless steel
Brass
Properties of alloys
i. They are stronger and harder than their components.
ii. The are good conductor of heat and electricity.
iv. They are more brittle than their components.
iv. Their melting point is lower than that of their components.
Metalloids
Metalloids are the elements having properties of both metals and non-metals, e.g. silicon,
arsenic, germanium, etc. Metalloids are semi-conductors.
Properties of metalloids
i. They are poor conductors of heat and electricity.
ii. They are not malleable and ductile.
iii. They are lustrous.
iv. They form alloys.
Role of Metals in Organisms
Different types of metals and non-metals are found in human body. Human body consists
of metals like Na, K, Ca, Mg, Fe, Cu, Zn, etc. Similarly, non-metals like C, H, N, O, P, S,
etc. are found in human body. These metals and non-metals are found in the form of
different compounds. These metals and non-metals are essential to form protein, nucleic
acid, lipids, etc. These elements are called biological inorganic compounds. The presence
of iron in blood was known to human beings in the 17th century. In human body, metals
like Na, Mg, K and Ca are found in more amount and metals like Mn, Co, Cu, Fe, Zn, Mo,
etc. are found less in amount in trace amount in human body.
GREEN Science (Chemistry) Book-9 217
Zinc in Enzyme
In the body of living organisms, zinc is found very less in amount. But it is a very important
metal for living beings. Zinc is found in about 300 enzymes of human body. In the body of
adult human beings, about 2-3 gram of zinc is found. Zinc is found in cells, tissues, bone,
cytoplasm, etc. About 90% of zinc present in the body is found only in muscles and bones.
Similarly, semen and prostate gland contain high concentration of zinc. Similarly, retina
of eye also contains zinc. The amount of zinc decreases along with age which results in
blurred vision.
Role of zinc in human body
In human body, zinc is essential:
1. to increase immunity against diseases.
2. to prevent in the infection of diarrhoea, pneumonia, etc.
3. for the development of embryo.
4. for increasing height and weight of small children.
5. for development of bones.
6. to increase the fertility of males.
7. to regulate menstrual cycle in females.
8. to treat diseases like psoriasis and neurodermitis.
9. to taste and smell food items.
10. to treat anorexia.
Importance of Sodium and Potassium ions
In human body, sodium and potassium ions are found in the form of ions, i.e. Na+ and K+.
Those ions are very important for our body. These ions are found inside and outside the
cells. Nervous system can work only in the presence of charged ions. In our body, various
metabolic activities occur due to exchange of sodium and potassium ions.
Sodium-potassium pump is a very important process for human body. In this process,
when sodium ions enter the cells, potassium ions leave the cells. This process occurs
simultaneously. Exchange of information between brain and neurons occur due to
sodium-potassium pump. This process is essential for regulating body temperature and
heart beat. It is also essential to keep muscles fit and to control pH inside cells.
If there is irregularity in sodium potassium pump, we suffer from paralysis, migraine,
muscle spasm, etc. Therefore, proper balance of sodium and potassium ions in the body
is essential to live a healthy life.
218 GREEN Science (Chemistry) Book-9
Harmful Effects of Lead
Lead is a harmful element for human body. Like other useful metals, lead also spreads
throughout the body and affects almost all organs. The adverse effects seen in human
body due to entry of lead are given below:
i. Headache
ii. Abdominal pain Do You Know
iii. Anaemia
iv. Change in behaviour Lead affects the brain of children
v. Lack of brain development adversely. It also affects the absorption of
calcium by bones.
vi. Weakening of bones
Harmful Effects of Mercury
Mercury is a poisonous metal for human body. When a single drop of mercury enters
our body it may block blood vessels and causes death of the victim. The compounds of
mercury are very harmful for our body. They also affect the foetus by entering through
placenta. It affects the physical and mental development of foetus. The harmful affects of
mercury in human body are given below:
i. Mercury affects the brain.
ii. It weakens the ability to speak, hear and see things.
iii. It affects the lungs and kidneys. Do You Know
iv. It affects the physical and mental The harmful affect of mercury in human
development of foetus adversely. body is called hydrargia or mercurialism.
Key Concepts
1. Metals are those substances which are hard, malleable, ductile and good conductors
of heat and electricity. For example, iron, copper, aluminium, gold, silver, etc.
2. Metals are used for making cooking utensils, construction materials, vehicles,
ornaments, furniture, electric wires, weapons, etc.
3. Most metals are malleable, i.e. they can be beaten into thin sheets.
4. Most metals are ductile, i.e. a thin and long wire can be made from metals.
5. Metals are good conductor of heat and electricity.
6. The property of a metal be virtue of which it can be drawn into a long wire is called
ductility.
7. When metals are stretched the positively charged ions and electrons in required
amount are stretched slowly. As a result, the metal changes into a wire.
8. Non-metals are those substances which are generally soft, non-malleable, non-
ductile and bad conductors of heat and electricity.
9. We use many non-metals in our daily life. Non-metals are used in construction
works, to make containers, utensils, medicines, etc.
10. Non-metals are found in all three states, i.e. solid, liquid and gas.
GREEN Science (Chemistry) Book-9 219
11. Different types of metals and non-metals are found in human body. Human body
consists of metals like Na, K, Ca, Mg, Fe, Cu, Zn, etc. Similarly, non-metals alike C,
H, N, O, P, S, etc. are found in human body.
12. In the body of living organisms, Zinc is found very less in amount. But it is a very
important metal for living beings.
13. Retina of eye also contains zinc. The amount of zinc decreases along with age which
results in blurred vision.
14. In human body, sodium and potassium ions are found in the form of ions, i.e. Na+
and K+. Those ions are very important for our body.
15. In our body, various metabolic activities occur due to exchange of sodium and
potassium ions.
16. Sodium-potassium pump is a very important process for human body. In this
process, when sodium ions enter the cells, potassium ions leave the cells. This
process occurs simultaneously.
17. If there is irregularity in sodium potassium pump, we suffer from paralysis,
migraine, muscle spasm, etc.
18. Lead is a harmful element for human body. Like other useful metals, lead also
spreads throughout the body and affects almost all organs.
19. Lead affects the brain of children adversely. It also affects the absorption of calcium
by bones.
20. Mercury is a poisonous metal for human body. When a single drop of mercury
enters our body it may block blood vessels and causes death of the victim.
21. Mercury affects the brain. It weakens the ability to speak, hear and see things. It
affects the lungs and kidneys.
22. The harmful affect of mercury in human body is called hydrargia or mercurialism.
Sequential General Exercise 1
1. Choose the best answer from the given alternatives.
a. Which of the following elements is a metal?
oxygen iron
nitrogen carbon
b. Which of the given metal has very low melting point?
potassium iron
copper aluminium
220 GREEN Science (Chemistry) Book-9
c. What is the boiling point of magnesium? 1107°C
650°C
1083°C 2567°C
d. Anorexia is caused due to lack of .................. in human body.
calcium potassium
zinc copper
e. Which of the given metals is harmful for human body?
sodium potassium
iron mercury
2. Answer the following questions.
a. Define metals. Write three examples of metals.
b. Write down the general properties of metals.
c. Define the following terms.
i. Conductivity
ii. Malleability
iii. Ductility
d. Define non-metals with any four examples.
e. Write any two chemical properties of metals.
f. Write any four general properties of non-metals.
g. Define alloys with any two examples.
h. Name any five metals and five non-metals that are found in human body.
i. Name any two metals having low melting point and two metals having high
melting point.
j. What is meant by sodium-potassium pump? Why is it essential for human body?
k. Name any two diseases that are caused due to lack of zinc in our body.
l. What is the poisonous effect of mercury in human body called?
3. Write any four differences between metals and non-metals.
4. Describe an experiment to prove that metals are good conductors and non-metals
are bad-conductors of heat.
GREEN Science (Chemistry) Book-9 221
5. Describe in brief the role of metals in organisms.
6. Write down the role of zinc in human body.
7. Why are sodium and potassium ions important for human body?
8. List the harmful effects caused due to lead and mercury in human body.
9. Copper is called a metal but carbon is called a non-metal, why?
10. Why is brass called an alloy? Give reason.
Grid-based Exercise 2
Group ‘A’ (Knowledge Type Questions) (1 Mark Each)
1. What are metals ?
2. Name any two soft metals. ?
3. What are non-metals ?
4. What do you mean by metalloids ?
5. What do you mean by ductility?
6. Name a metal and a non-metal having more density.
7. Write any two physical properties of metals.
8. Name any two metals which can be changed into sheets on beating.
9. Name any two metals which cannot be drawn into wire.
10. Write down the melting point of the given metals:
i. sodium ii. iron
iii. copper iv. potassium
11. What happens when the solution of silver nitrate is electrolysed? Write.
12. Write down the boiling points of the given metals:
i. sodium ii. copper
iii. potassium iv. Iron
13. Name any two metals which are not ductile.
For Group ’B’ (Understanding Type Questions) (2 Marks Each)
14. Why is the melting point of potassium very less than that of iron although both are
metals? Give reason.
15. Write any two differences between metal and non-metal.
16. Sulphur is called non-metal and Brass is called an alloy. Give reason.
17. Why is essential to balance in sodium and potassium pump ? Silicon is called a
metalloid. Give reason.
18. Zinc is a very essential element for human body, why ?
19. What is meant by sodium-potassium pump ?
20. Metals are very important in our daily life. Give reason.
222 GREEN Science (Chemistry) Book-9
For Group ‘C’ (Application Type Questions) (3 Marks Each)
21. List the harmful effects of mercury and lead in human body. Name a non-metal which
is good conductor of heat and electricity.
22. What happens when the solution of silver nitrate is electrolysed? Write ionic equation.
23. Write a short note on "Zinc in Enzyme." Name a non-metal that forms electropositive
ion.
24. 'Describe in brief the role of metals in human body.
25. Describe in brief the role of zinc in human body.
For Group ‘D’ (Higher Abilities Type Questions) (4 Marks Each)
26. What is the reason behind that the melting and boiling point of iron is more than that
of sodium? Write any two differences between metalloids and alloys.
27. Complete the given chemical equations:
i. Mg + HCl .... ii. Na + HNO3 .....+ H2
iv. K + ..... K2SO4 + H2
iii. H2 + K .....
28. What happens when?
i. Sodium reacts with hydrochloric acid
ii. Potassium sulphate is electrolysed
iii. Copper sulphate is electrolysed
iv. Magnesium chloride is electrolysed
29. Describe in brief the role of sodium and potassium ions in the bodies of living beings.
30. Complete the given ionic equations. Differentiate between malleability and ductility.
i. NaCl ......... + Cr–
ii. CuSO4 Cu++ +
GREEN Science (Chemistry) Book-9 223
UNIT Carbon and its
Compounds
13
Weighting Distribution Theory : 6 Practical: 0
Before You Begin
Carbon is the most essential element for existence of plants and
animals. The atomic number of carbon is 6 and its atomic weight is
12. The valence shell of carbon consists of four elements. Therefore,
carbon combines with elements like hydrogen, oxygen, etc. forming
covalent bond. The word carbon has been derived from the Latin word
'carbo' which means shoot or charcoal. Carbon is present in various
organic as well as inorganic compounds. Carbon is found in living
beings as well as non-living things. Carbon combines with hydrogen
and forms many hydrocarbons. In this unit, we will study about
sources and nature of carbon, allotropes of carbon and properties
of carbon. Similarly, we will study about organic compounds and
inorganic compound in brief.
Learning Objectives Syllabus
After completing the study of this unit, students will be able to:
i. define hydrocarbons and explain their forms. • Structure, nature and sources
of carbon
ii. state physical and chemical properties of carbon.
• Physical and chemical
iii. introduce allotropes of carbon. properties of carbon
iv. introduce inorganic and organic compounds and • Diamond and graphite
differentiate between them.
• Organic compounds and
organic compounds
Glossary: A dictionary of scientific/technical terms
hyrocarbon : the compounds made of hydrogen and carbon
organic : obtained from living beings
inorganic : obtained from minerals
allotropes : the different forms of an element having different physical properties and
diamond similar chemical properties
: hardest and purest form of carbon
224 GREEN Science (Chemistry) Book-9
Carbon and Its Compounds
The word carbon is derived from the Latin word 'carbo' which means charcoal or shoot.
Human beings were familiar with carbon in the form of charcoal and shoot since prehistoric
day. These are the types of carbon. Later human beings discovered that diamond and graphite
are made up of carbon only. These compounds can be obtained naturally. According to
scientists different carbon compounds has been discovered in last 20 years, whose use can
bring lots of change in the entire world.
Carbon is a non-metal which forms covalent bond with other four carbon atoms. Carbon
also forms covalent bond easily with other elements too. Due to this property of carbon
there are nearly ten million carbon compounds present in the world. In this unit, we will
discuss the properties and compounds of carbon.
Carbon in common materials
Carbon is the basis of construction of all living organisms. Different types of carbon atoms are
found throughout our body. Carbon is contained in animal and plant cell as a basic element.
Generally carbon is black in colour. If any substance burns giving softy flame or smoke
and the remnant of burning solid substance appear black. It proves there is carbon in that
solid substance.
Activity 1
Collect some materials like wood, sugar, ghee, edible oil, kerosene, tongs, spatula,
burner, match box and observe the following activities.
At first take a piece of wood with the help of tongs and heat it with a burner.
Take edible oil, ghee, kerosene in spatula and heat it with a burner and observe.
Take a little amount of sugar in a spoon and heat it with a burner. At first sugar melts
and turns into yellowish grupy mass. On further heating it turns into greenish mass
called caramel which on further heating gives black sugar charcol. It proves that
sugar contains carbon.
Carbon element is ranked at 6th place in the world in terms of most available elements.
It is the second element of human body.
Sources of Carbon
In terms of element Carbon in terms of compound Carbon in terms of gas
Inorganic compounds organic compound
coal carbonates, carbohydrates, carbon dioxide,
coke bicarbonates,
charcoal carbides (like CaC2), protein, carbon monoxide,
diamond minerals, stones, etc.
graphite petrol, hydrocarbon gases
graphene
vitamins, (like methane, ethane,
medicines, LPG, etc.)
silk, soap, paper,
etc.
GREEN Science (Chemistry) Book-9 225
Nature of Carbon
Carbon atom has four valence electrons. So, it has equal chance of gaining or losing electron
to obtain stable electronic configuration. Its valency is four. Carbon shares its electrons
with atoms of either same element or other elements to form covalent compounds. As it
can form four covalent bonds, its valency is called tetravelency.
A carbon atom forms four covalent bonds with hydrogen atoms by sharing electrons
and form a methane molecule. In fact, the number of carbon compounds alone is much
greater than the number of compounds formed by all other elements. The reason for the
existence of the large number of carbon compounds is that the carbon atoms can link
with one another by strong covalent bonds of long chains or rings of carbon atoms. The
property of carbon element due to which its atoms can join with one another to form a
long carbon chain is called catenation. Due to this property, there exists large number of
carbon compounds.
For example: CCCC CCCCC
Covalent bond
C
The branch of chemistry dealing with carbon and its compounds is known as organic
chemistry and that dealing with other than carbon is known as inorganic chemistry.
There are various forms of carbon because of its covalency. When an element in its different
forms, shows the same chemical properties but different physical properties, such forms
are known as allotropes and the phenomenon is called allotropy or allotropism.
Carbon allotropes
crystalline amorphous
diamond graphite fullerenes coal coke charcoal lamp black
Do You Know
Graphite is also called black lead.
Physical Properties of Carbon
1. Carbon is found in solid state. Diamond and graphite are crystalline but coal and
charcoal are found in amorphous form.
2. Carbon is insoluble in water.
3. At very high temperature carbon is directly converted into gaseous state from solid
state.
4. Carbon is black in colour but diamond is colourless and transparent.
5. Carbon has no shining property but diamond is shiny.
6. Carbon is bad conductor of heat and electricity but graphite is good conductor of heat
and electricity.
7. The density of carbon may vary from 1.5 to 3.5 depending on its different allotropes.
226 GREEN Science (Chemistry) Book-9
Diamond
It is the purest from of carbon and is the hardest natural substance known. It is non-
conductor of heat and electricity. The diamond crystals found in nature are octahedral and
the carbon atoms are strongly bound to each other which leads to its hardness. It is used
for cutting purposes like plastic, marble, etc. Diamond is transparent to X-ray. It does not
take part in chemical reaction but burns at temperature of 850°C. It is an expensive crystal.
Do You Know Fig. Fig.13.1
In a diamond crystal, each carbon atom is combined
to four other carbon atoms by covalent bonds.
Hence all the four valence electrons of each carbon
atom are used up in the bond formation without
leaving free electrons. As a result, diamond cannot
conduct heat and electricity. Therefore, diamond is
a bad conductor of heat and electricity.
Diamond
Graphite
In graphite, the atoms of carbon arrange themselves into hexagonal layer and each carbon
forms a covalent bond with three other carbons. These hexagonal layers are arranged in
two dimension. In a single piece of graphite the hexagons are arrange one over another.
So, one layer of graphite can slip easily over one another. Thus it is soft and slippery
and hence can be used as a lubricant. The lead of pencil is made of a mixture of graphite
and clay. Since, graphite is a good conductor of electricity and hence can be used as an
electrode.
Do You Know 13.2
In a graphite crystal, each carbon atom is connected
to only three other carbon atoms by covalent bonds.
The fourth valence electron of each carbon atom is
free to move. As a result, graphite can conduct heat
and electricity due to presence of free electrons.
Therefore, graphite is a good conductor of heat and
electricity though it is a non-metal.
Graphite
Differences between Diamond and Graphite
Diamond Graphite
1. It is bad conductor of heat and 1. It is good conductor of heat and
electricity. electricity.
2. It is the hardest substance. 2. It is soft and slippery.
3. It is a transparent crystalline substance. 3. It is a dark grey opaque substance.
4. Its specific gravity is 3.52. 4. Its specific gravity is 2.2.
GREEN Science (Chemistry) Book-9 227
Chemical Properties of Carbon
1. Combustion : Carbon burns in air to form carbon dioxide but it forms carbon
monoxide if it burns in insufficient oxygen.
C + O2 burn in sufficient oxygen CO 2 + heat and light
C + O burn insufficient oxygen CO + heat and light
2
2. Reduction Property
a. When carbon is heated with oxides of less active metals, carbon dioxide is formed
separating the metals.
2ZnO + C 2Zn + CO2
2PbO + C 2Pb + CO2
b. Carbides can be obtained from the reaction between carbon and silica or calcium
oxide.
SiO2 + 3C Si C + 2CO
2Ca O + 6C 2Ca C2 + 2CO Do You Know
3. Reaction with steam: When carbon is heated
vigorously with water vapour (∼1000°C) Silicon carbide (SiC) is man-made
carbon monoxide and hydrogen gases are substance. It is hard like diamond.
formed. The mixture of carbon monoxide
and hydrogen is called water gas. It is used as a source of heat.
C + H2 O ∼ 1000° C CO + H2
(Vapour) (water gas)
Organic and Inorganic Compounds
Organic compounds
The compounds formed by the reaction of carbon with carbon with hydrogen or other
elements by forming covalent bond are called organic compounds. In organic compounds,
carbon forms covalent bond with other elements like oxygen, nitrogen, halogen, sulphur,
phosphorus, etc. However, the compounds like CO2, CaCO3, MgCO3, Ca(HCO3)2 etc. are
not organic compounds even they contain carbons.
Generally, organic compounds are made up of seven elements carbon, hydrogen, oxygen,
nitrogen, halogen, sulphur and phosphorus. Some metals are also form covalent bond in
organic compounds. Methane, ethane, propane, butane, wax, petrol, kerosene, alcohol,
ether, glycerol, carbohydrate, acid, benzene, nephthalene, oil, etc. are the examples of
organic compounds.
Inorganic compounds
Inorganic compounds are formed by other 118 elements of the periodic table. But some
elements do not contain carbon. These compounds have electrovalent bonds or covalent
bonds or both. Examples: NaCl, CaCo3, H2SO4, MgCO3, etc.
228 GREEN Science (Chemistry) Book-9
Difference Between Organic and Inorganic Compounds
Parameter Organic compounds Inorganic compounds
1. State These are found in all three These are mostly found in solid
states, viz. solid, liquid and state but some are found in both
gas. liquid and gaseous states.
2. Colour and Mostly, they have colour and Mostly, they do not have color
smell smell (the smell of flowers as and smell. However, some metal
well as smell of citric fruits is compounds have colour as well
due to organic compounds). as ammonia and its compounds
have smell too.
3. Solubility They are generally insoluble They generally dissolve in water
in water but soluble in but do not dissolve in inorganic
organic liquids. (Oil is solvents. (Salt dissolves in water
insoluble in water but soluble but does not dissolve in ether.)
in ether). They generally do not burn on
heating. They have high boiling
4. Combustibility Most of them burn on and melting points.
heating. (e.g. petrol, oil, LPG,
etc.) They ionize.
5. Melting and They have low boiling and
boiling point melting point. Vaseline melts
at 37°C.
6. Ionization They do not ionize.
7. Bonds They have covalent bonds. They have electrovalent bonds.
Sequential General Exercise 1
1. Choose the best answer from the given alternatives.
a. Which one of the following is colourless and transparent allotrope of carbon?
Diamond Charcoal
Graphite Coal
b. Which gas is evolved during chemical reaction between zinc oxide and carbon?
Carbon dioxide Carbon monoxide
Nitrogen dioxide Sulphur dioxide
c. Which of the following mixture of gas is called water gas?
CO2 + H2 CO2 + O2
CO + O2 CO + H2
GREEN Science (Chemistry) Book-9 229
d. Which one of the following is an inorganic compound?
Ethyl alcohol Acetic acid
Carbon dioxide Methane gas
2. Answer the following questions.
a. Write any five sources of carbon. Also, write down any five physical properties of
carbon.
b. How do you prove that sugar contains carbon? Write in brief.
c. What do you mean by catenation? Describe with examples.
d. What is allotropy? Write any three allotropes of carbon.
e. Write any three properties of diamond.
f. Write any three properties of graphite.
3. Differentiate between:
a. Diamond and Graphite
b. Graphite and Charcoal
c. Diamond and Coal
d. Organic compound and Inorganic compound
e. Allotropes and Allotropism
4. Write any three chemical properties of carbon with balanced chemical equations.
5. What do you mean by organic and inorganic compounds? Write with examples.
6. Diamond cannot conduct electricity but graphite can, why?
7. Why do organic compounds not undergo electrolysis?
8. What happens when?
a. carbon is burnt in insufficient oxygen
b. carbon is burnt in sufficient oxygen
c. carbon is heated with less reactive metals
d. carbon is heated vigorously with water vapour
e. carbon reacts with lime
9. Complete the given chemical equations.
a. C + ................ CO
b. C + H2O ............... + H2
230 GREEN Science (Chemistry) Book-9
c. PbO + ............ 2Pb + .....................
d. CuO + C ................. + CO2
10. Name the type of bond found in organic compounds.
11. Name the type of bond found in inorganic compounds.
12. What is water gas? Why it is used?
Grid-based Exercise 2
Group ‘A’ (Knowledge Type Questions) (1 Mark Each)
1. Define organic chemistry.
2. Define organic compound.
3. What is a hydrocarbon?
4. What is catenation?
5. What is a saturated hydrocarbon?
6. Define unsaturated hydrocarbon.
7. Write down the position of carbon in the Modern periodic table.
8. What are the different sources of carbon found in nature?
9. Define allotropes and allotropism.
10. What is a crystalline substance?
11. Write any two properties of amorphous carbon.
12. Write any two properties of diamond.
13. Write any two properties of graphite.
For Group ’B’ (Understanding Type Questions) (2 Marks Each)
14. Write any two differences between saturated hydrocarbon and unsaturated
hydrocarbon.
15. Diamond cannot conduct electricity but graphite can. Give reason.
16. Why is diamond called crystalline substance ? Generally, organic compounds burn
on heating. Give reason.
17. Alcohol is called an organic compound, but carbon dioxide is called an inorganic
compound, why ? Give reason.
18. Butane is called saturated hydrocarbon and butene is called unsaturated hydrocarbon,
why ?
19. Why is carbon kept in the group IVA of the periodic table? Give reason. Why is
methane called hydrocarbon?
20. Write any two differences between diamonds any graphite.
GREEN Science (Chemistry) Book-9 231
For Group ‘C’ (Application Type Questions) (3 Marks Each)
21. Write down the methods of naming hydrocarbons with an example.
22. What happens when carbon is burnt in air? Write with chemical equation. Write
down the position of carbon in the Modern periodic table.
23. How can you prove that sugar consists of carbon? Write in brief.
24. Write any three properties of graphite.
25. What happens when carbon is burnt in insufficient oxygen? Write with the chemical
equation.
For Group ‘D’ (Higher Abilities Type Questions) (4 Marks Each)
26. Prepare a list of various sources of carbon in the form of element, compound and gas.
27. Write any two chemical properties of carbon with balanced chemical equation.
28. Define allotrope and prepare a list of various allotrope of carbon.
29. What happens in the following conditions? Write with chemical equation.
i. When carbon reacts with lead oxide
ii. When copper oxide reacts with carbon
30. Define isomerism and write down the possible isomers of pentane.
232 GREEN Science (Chemistry) Book-9
UNIT Water
14
Weighting Distribution Theory : 4 Practical: 2
Before You Begin
Water (H2O) is a chemical substance formed by a combination of
hydrogen and oxygen. One molecule of water consists of two atoms of
hydrogen and one atom of oxygen. Water is the most useful chemical
substance found in nature. About 71 percent of the earth is covered
with water.
Water exists in three different states. They are solid, liquid and
gas. In air, water remains in the form of vapour and cloud. In high
mountains, water remains in the form of ice or snow. In ponds, lakes,
rivers, oceans, etc., water is found in liquid state.
Underground water is another source of water. It is obtained from
well, tube well, etc. Water is used for bathing, washing, drinking,
cooking, irrigating , swimming, etc. It is also used in industries.
In this unit, we will study the sources, properties and uses of water.
Similarly, we will study types of water and methods of removing
hardness of water in brief.
Learning Objectives Syllabus
After completing the study of this unit, students will be able to:
i. introduce water. • Introduction to water
ii. describe the sources, properties and uses of water. • sources of water
iii. explain the methods of removing hardness of water • Properties of water
with chemical equations.
• Uses of water
• Hard water and soft water
• Methods of removing
hardness of water
Glossary: A dictionary of scientific/technical terms
glaciers : sources of water found in Himalayas
aquifer : a layer of rock or soil that can absorb and hold water
soft water : the water without soluble salts of calcium and magnesium
hard water : the water containing soluble salts of calcium and magnesium
GREEN Science (Chemistry) Book-9 233
Sources of water
We get water from river, stream, fountain, pond, lake, etc. for daily use. These are called
sources of water. We obtain water for various sources for drinking, bathing, washing,
irrigating, cleaning, etc. The different sources of water available on the earth are given below.
Sources of water on the earth
Water in sea/ocean Other sources of water
Snow or ice Surface water Underground water
Pond, lake River Wetlands
On the basis of availability, the sources of water on the earth are divided into following
two types.
1. Surface water resources 2. Ground water resources
1. Surface water resources
Seas or oceans contain about 97% of
water. But this water is not suitable for
daily use as it is rich in salt. However,
this water can be used for boating and
transportation. Similarly, it can be
utilized to generate hydroelectricity
from tides.
Fig.
Fig.
Other sources of surface water available
on the earth are river, lake, pond, 14.1
stream, fountain, etc. We use water from
Sea
these sources for various purposes like
cooking, drinking, bathing, washing, irrigating, etc. Similarly, we use water from these
sources to run factories and generate hydroelectricity.
14.2 Lake Fountain
River
234 GREEN Science (Chemistry) Book-9
2. Ground water resources Do You Know
The water during rainfall is absorbed by Ogallala aquifer is the largest aquifer
soil and it is stored under the ground. throughout the world. It touches eight states
This water is called ground water. We of USA. The area of this aquifer is 4,50,000
can draw this water by digging the earth. km2.
The ground water thus collected consists
of porous rocks, sand and silt, which is
called aquifer. There is a large amount
of water in aquifers. They contain
hundreds time more water than that
of rivers, ponds, lakes, etc. The level of
underground water is called water table.
The underground water may contain
many impurities. So, it is not suitable for
direct consumption. Underground water
comes out through cracks in rocks in the
form of fountains, spouts, etc. We can
use this water for various purposes.
Physical Properties of Water
1. Water exists in all three states, i.e. solid, liquid and gas.
2. It is transparent.
3. It is a bad conductor of heat and electricity.
4. Pure water is colourless, odourless and tasteless.
5. It is a universal solvent.
6. It freezes at 0 °C and boils at 100 °C.
7. It is a neutral substance. Pure water is neither acidic nor basic in nature.
Activity 1
Take a leaf of Colocasia.
Put a few drops of water on the upper surface of leaf.
Observe the shape of water drops.
The drops of water appear as round shiny ball. It occurs due to more cohesive force
among the molecules of water and less adhesive force between the molecules of water
and these of Colocasia.
GREEN Science (Chemistry) Book-9 235
Chemical Properties of Water
1. Water decomposes into hydrogen and oxygen gas when electolysed.
2H2O electrolysis 2H2 + O2
2. Water reacts with carbon dioxide and forms carbonic acid.
H2O + CO2 H2CO3
3. Water reacts with very active metals like lithium (Li), sodium (Na), calcium (Ca), etc.
and produces metal hydroxide (alkali) and hydrogen gas.
Ca + H2O Ca(OH)2 + H2
2Na + H2O 2NaOH + H2
2Li + H2O 2LiOH + H2
4. Water dissolves acid, base and salt and decomposes them into their ions.
HCl +H2O H+ + Cl–
H2SO4 +H2O 2H+ + SO4– –
Na+ + OH–
NaOH +H2O
KOH +H2O K+ + OH–
NaCl +H2O Na+ + Cl–
KCl +H2O K+ + Cl–
5. Pure water does not conduct electricity but solution of water with acid, base or salt
conducts electricity.
Solvent Properties of Water
A variety of substances dissolve in water. So water is called a universal solvent. Acids,
alkalis, salts and other compounds like sugar, glycerol, urea, etc. dissolve in water. Most
electrovalent compounds or ionic compounds like Calcium chloride (CaCl2), Potassium
chloride (KCl), Sodium nitrate (NaNO3), etc. dissolve in water. But compounds like
Barium sulphate (BaSO4), Calcium fluoride (CaF2), etc. do not dissolve in water.
Some covalent compounds like alcohol, glucose, urea, etc. also dissolve in water. But
covalent compounds like methane, carbon tetrachloride, etc. do not dissolve in water.
Water is widely used as a solvent.
Uses of Water
1. Water is used for generating hydroelectricity.
2. It is used for cooking, drinking, bathing, washing, etc.
236 GREEN Science (Chemistry) Book-9
3. Water is used for cooling the hot engines of vehicles.
4. Water is used for irrigating crops.
5. Water is used by green plants for photosynthesis.
6. Water is used in industries to produce various substances, to purify metals, to cut
minerals, etc.
7. Water is used for boating, swimming, rafting, etc.
8. Water is used for transportation.
9. Water is used to dilute acids.
10. Water is used to make solutions of various chemicals.
Types of Water Fig. Fig.
On the basis of absence or presence of chemicals dissolved in it, water is of two types, viz.
(a) soft water and (b) hard water.
a. Soft water
The water which does not contain chloride, sulphate
and bicarbonate salts of magnesium and calcium is
called soft water. It produces more lather with soap,
e.g. distilled water and rain water.
14.3
b. Hard water
The water which contains chloride, sulphate and
bicarbonate salts of magnesium and calcium is called
hard water. It produces less lather with soap. So hard
water is not suitable for washing clothes. Spout water
and water of wells, rivers, oceans, etc. is hard.
14.4
Differences between Soft water and Hard water
Soft water Hard water
1. It does not contain soluble salts of 1. In contains soluble salts (chloride,
magnesium and calcium. sulphate and bicarbonate) of
magnesium and calcium.
2. It produces more lather with soap. 2. It produces less lather with soap.
Types of hardness of water
On the basis of salts dissolved in it, hardness of water is of two types, viz. (a) temporary
hardness and (b) permanent hardness.
GREEN Science (Chemistry) Book-9 237
a. Temporary hardness
The hardness of water due to dissolved bicarbonate salts of magnesium and calcium is
called temporary hardness of water. Temporary hard water is tasty and makes bones
healthy.
Temporary hardness can be removed by boiling hard water or treating it with lime-water.
i. By boiling water
When temporary hard water is boiled, the soluble bicarbonate salts of magnesium and
calcium decompose into water insoluble carbonate salts, and settle down at the bottom of
the container. These salts can be separated by filtration.
Magnesium bicarbonate heat Magnesium carbonate + Water + Carbon dioxide
Mg(HCO3)2 MgCO3 + H2O + CO2
Calcium bicarbonate heat Calcium carbonate + Water + Carbon dioxide
Ca(HCO3)2 CaCO3 + H2O + CO2
i. By treating with lime-water or Clark's method
When temporary hard water is treated with lime-water or calcium hydroxide [Ca(OH)2],
a chemical reaction takes place. As a result, insoluble calcium carbonate is formed which
makes water soft. This method is also called Clark's method.
Magnesium + Calcium Calcium + Water + Magnesium
bicarbonate hydroxide carbonate hydroxide
Mg(HCO3)2 + 2Ca(OH)2 2CaCO3 + 2H2O + Mg(OH)2
Calcium + Calcium Calcium + Water
bicarbonate hydroxide carbonate
Ca(HCO3)2 + Ca(OH)2 2CaCO3 + H2O
b. Permanent hardness
The hardness of water due to presence of chloride and sulphate salts of magnesium and
calcium is called permanent hardness of water.
The permanent hardness of water can be removed by treating hard water with washing
soda and permutit process.
238 GREEN Science (Chemistry) Book-9
i. By treating permanent hard water with washing soda
When permanent hard water is treated with washing soda or sodium carbonate, the salts
present in it change into carbonates and water becomes soft.
Magnesium + Sodium Magnesium + Sodium
chloride carbonate carbonate chloride
MgCl2 + Na2CO3 MgCO3 + NaCl
Magnesium + Sodium Magnesium + Sodium
sulphate carbonate carbonate sulphate
MgSO4 + Na2CO3 MgCO3 + Na2SO4
Calcium + Sodium Calcium + Sodium
chloride carbonate carbonate chloride
CaCl2 + Na2CO3 CaCO3 + 2NaCl
Calcium + Sodium Calcium + Sodium
sulphate carbonate carbonate sulphate
CaSO4 + Na2CO3 CaCO3 + Na2SO4
ii. By permutit process
In this process, the permanent hard water is passed through sodium zeolite (Na2–Z) or
Sodium aluminosilicate (Na2Al2SiO8). As a result, the calcium and magnesium ions of
hard water are replaced by sodium ions of permutit and water becomes soft.
Hard water Sodium chloride
Soft water
Zeolite
ColumnFig.
Fine gravel
14.5
Permutit process
GREEN Science (Chemistry) Book-9 239
Differences between Temporary hard water and Permanent hard water
Temporary hard water Permanent hard water
1. It contains soluble bicarbonate salts of 1. It contains soluble chloride and
magnesium and calcium. sulphate salts of calcium and
magnesium.
2. Temporary hardness can be removed 2. Permanent hardness can be removed
by boiling water or treating it with by treating water with washing soda
lime water. or by permutit method.
Activity 2
Collect sample of water from different sources and keep them in separate test tubes.
Keep a few drops of liquid soap or shampoo in each test tube and stir them with
glass rod.
Observe which sample produces more lather.
Identify soft water and hard water from the collected sample of water.
Activity 3
Take a beaker and put some water into it.
Put some magnesium bicarbonate or calcium carbonate into the beaker and stir it
with a glass rod.
Now, put a few drops of liquid soap or shampoo and stir it. Does it produce lather
easily? The water does not produce lather easily. It shows that the water is hard and
the hardness is temporary.
Now, boil the water for a few minutes. Put a few drops of shampoo or liquid soap
and stir it with a glass rod.
The water produces lather with soap or shampoo after boiling.
It proves that temporary hardness of water can be removed by boiling.
Activity 4
Take a beaker with some water in it.
Put some calcium chloride or calcium sulphate into water and stir it with a glass
rod.
Put a few drops of liquid soap or shampoo and stir with a glass rod. The water
does not produce lather easily. It shows that the water is hard and the hardness is
permanent.
Now, put some sodium carbonate (washing soda) into the water and stir it with a
glass rod.
Now, put a few drops of liquid soap and shampoo in the beaker and stir it with a
glass rod.
The water produces lather easily. It shows that permanent hardness of water can be
removed by adding washing soda (Na2CO3).
240 GREEN Science (Chemistry) Book-9
Key Concepts
1. Water (H2O) is a chemical substance formed by a combination of hydrogen and
oxygen.
2. Water exists in three different states. They are solid, liquid and gas. In air, water
remains in the form of vapour and cloud. In high mountains, water remains in the
form of ice or snow. In ponds, lakes, rivers, oceans, etc., water is found in liquid
state.
3. We get water from river, stream, fountain, pond, lake, etc. for daily use. These are
called sources of water.
4. Seas or oceans contain about 97% of water. But this water is not suitable for daily
use as it is rich in salt.
5. We use water from these sources for various purposes like cooking, drinking,
bathing, washing, irrigating, etc. Similarly, we use water from these sources to run
factories and generate hydroelectricity.
6. The ground water consists of porous rocks, sand and silt, which is called aquifer.
There is a large amount of water in aquifers.
7. The underground water may contain many impurities. So, it is not suitable for
direct consumption.
8. Pure water is colourless, odourless and tasteless.
9. Water freezes at 0 °C and boils at 100 °C.
10. Water reacts with very active metals like lithium (Li), sodium (Na), calcium (Ca),
etc. and produces metal hydroxide (alkali) and hydrogen gas.
11. Pure water does not conduct electricity but solution of water with acid, base or salt
conducts electricity.
12. A variety of substances dissolve in water. So water is called a universal solvent.
13. Some covalent compounds like alcohol, glucose, urea, etc. dissolve in water.
14. Water is used in industries to produce various substances, to purify metals, to cut
minerals, etc.
15. On the basis of absence or presence of chemicals dissolved in it, water is of two
types, viz. (a) soft water and (b) hard water.
16. The water which does not contain chloride, sulphate and bicarbonate salts of
magnesium and calcium is called soft water.
17. The water which contains chloride, sulphate and bicarbonate salts of magnesium
and calcium is called hard water.
18. Temporary hardness can be removed by boiling hard water or treating it with lime-
water.
19. The hardness of water due to presence of chloride and sulphate salts of magnesium
and calcium is called permanent hardness of water.
20. The permanent hardness of water can be removed by treating hard water with
washing soda and permutit process.
21. When permanent hard water is treated with washing soda or sodium carbonate, the
salts present in it change into carbonates and water becomes soft.
GREEN Science (Chemistry) Book-9 241
Sequential General Exercise 1
1. Choose the best answer from the given alternatives.
a. Which of the following sources of water is not suitable for daily use?
sea river
fountain underground water
b. What is the boiling point of water? 100°C
0°C 0°F
100°F
c. Which of the given compounds does not dissolve in water?
Sodium chloride Potassium nitrate
Barium sulphate Calcium chloride
d. Which of the given chemicals causes temporary hardness of water?
Calcium sulphate Calcium bicarbonate
Calcium chloride Magnesium sulphate
2. Answer the following questions.
a. What are sources of water? Write their types.
b. Write a short note on surface water resources.
c. What is aquifer? Name the largest aquifer in the world.
d. Write down the physical properties of water.
e. Write any three chemical properties of water.
f. What is meant by cohesive property of water?
g. Name any four compounds that dissolve in water.
h. Write down the major uses of water.
i. What is meant by soft water?
j. What is meant by hard water?
k. What is meant by temporary hardness of water?
l. What is meant by permanent hardwater?
242 GREEN Science (Chemistry) Book-9
3. Differentiate between:
a. Surface water and underground water
b. Soft water and hard water
4. Why is sea water not suitable for drinking?
5. Write down the method of removing temporary hardness of water.
6. Describe the Clark's method for removing hardness of water.
7. What is permutit method? Explain with figure.
8. Describe the method to test whether the given sample of water is hard or soft.
Grid-based Exercise 2
Group ‘A’ (Knowledge Type Questions) (1 Mark Each)
1. Name any two sources of surface water.
2. Write any two physical properties of water.
3. Name any three ionic compounds that do not dissolve in water.
4. What is aquifer ?
5. What is "Water table" ?
6. What is "solvent property of water" ?
7. What is Clark's method ?
8. What is brine ?
9. What is temporary hardness of water ?
10. What is permanent hardness of water ?
11. Name any two covalent compounds that dissolve in water.
12. Write any two methods for removing permanent hardness of water.
For Group ’B’ (Understanding Type Questions) (2 Marks Each)
13. Why is water called a universal solvent ? Give reason.
14. Write any two differences between hard water and soft water.
15. Write any two differences between temporary hardness and permanent hardness of
water.
16. Why does water appear as a ball on Colocasia leaf. Give reason.
17. Temporary hardness of water can be removed by using calcium hydroxide, why ?
Give reason.
18. Temporary and permanent hardness of water can be removed by permutit process,
why?
19. Water is very useful for living beings. Give reason.
GREEN Science (Chemistry) Book-9 243
For Group ‘C’ (Application Type Questions) (3 Marks Each)
20. How is the permanent hardness of water removed by using washing soda? Write with
chemical equations.
21. How does underground water come on the surface ? Write any two utilities surface
water sources.
22. What happens when sodium metal is kept in water? Write with a balanced chemical
equation.
23. Write down the utility of brine. Describe in brief the importance of water in our body.
24. Which method is used to remove temporary and permanent hardness of water? Write.
For Group ‘D’ (Higher Abilities Type Questions) (4 Marks Each)
25. Write any two methods for removing permanent hardness of water.
26. Write any two differences between temporary and permanent hardness of water.
27. How is temporary hardness of water removed ? Write with chemical equations.
28. What is permutit method ? Write in brief with a neat and labelled figure.
244 GREEN Science (Chemistry) Book-9
UNIT Chemical Fertilizers
15 used in Agriculture
Weighting Distribution Theory : 6 Practical: 0
Before You Begin
Farmers use fertilizers to increase the fertility of soil. Fertilizers are
essential for growth and development of root, stem, leaves, flowers
and fruits. Plants require various nutrient elements like nitrogen,
phosphorus, potassium, boron, magnesium, iron, zinc, etc. Among
them, nitrogen (N), phosphorus (P) and potassium, (K) are the most
essential nutrient elements for plants. The substances that are used
to increase the fertility of soil are called fertilizers. On the basis of
source, there are two types of fertilizers. They are organic or compost
fertilizers and inorganic or chemical fertilizers. In this unit, we will
study about types of fertilizers, organic and inorganic fertilizers,
NPK fertilizers in brief.
Learning Objectives Syllabus
After completing the study of this unit, students will be able to:
i. introduce chemical fertilizers and state their types • Introduction to chemical
fertilizers
with examples.
• Types of fertilizers
ii. describe the uses of nitrogen, phosphorus and
potassium fertilizers. - organic fertilizer
iii. explain the effects in plants due to deficiency of - Inorganic fertilizer
nitrogen, phosphorus and potassium.
• Types and uses of nitrogenous
potassium and phosphorus
fertilizers
Glossary: A dictionary of scientific/technical terms
fertilizers : the substances that increase the fertility of soil
organic fertilizers : the fertilizers obtained by decaying parts of plants and animal wastes
inorganic fertilizer : the fertilizers obtained from minerals
NPK fertilizers : the fertilizers containing nitrogen, phosphorus and potassium
GREEN Science (Chemistry) Book-9 245
Fertilizers
When we plant same types of crops in soil for a long time, the fertility of soil decreases.
Therefore, we use fertilizers in soil to increase the productivity of crops. The substances
which are added to the soil to increase the productivity is crops are called fertilizers.
Fertilizers contain various nutrient elements like nitrogen, phosphorus, potassium,
sulphur, magnesium, iron, zinc, etc. These nutrient elements help in growth and
development of plants.
Types of Fertilizer
On the basis of source, there are two types of fertilizers. They are as follows:
1. Organic fertilizers or Compost manure
2. Inorganic fertilizers or Chemical fertilizers
1. Organic fertilizer or Compost manure
The organic manure produced by
decaying various parts of plants and
animal wastes is called compost manure.
It is added to the soil to increase the
fertility of the soil. Fertilizers are the
substances that increase the fertility
of soil. Compost manure is called an Fig.
organic fertilizer because it is produced
by decaying parts of plants and animal 13.1 Organic fertilizer
wastes.
Organic fertilizers are of two types. They are green manure and compost manure. Green
manure is produced by decaying various parts of plants whereas compost manure is
prepared by decaying parts of plants and animal wastes.
Some bacteria convert atmospheric nitrogen into nitrates and increase the fertility of soil.
Organic fertilizers do not contain all elements required for growth and development of
plants. So we should add chemical fertilizers to the soil to increase the productivity of crops.
Role of compost fertilizer Do You Know
1. The plants grown by using compost Organic fertilizers are prepared by using
fertilizers grow well and produce good dead and decaying parts of plants and
fruits. animals. They do not affect the quality of
soil.
2. They preserve water content in the soil.
3. They do not cause environment
pollution.
4. They prevent leaching and soil erosion.
5. They do not increase or decrease acidity or alkalinity of soil.
6. They are biodegradable.
7. They do not have negative impacts on atmosphere.
246 GREEN Science (Chemistry) Book-9
Disadvantages of organic fertilizers
1. Organic fertilizers do not contain all nutrient elements essential for plants.
2. They do not dissolve completely in water. So all organic fertilizers are not absorbed
by plants.
3. They are difficult to store and transport.
Chemical fertilizers or Inorganic fertilizers
The chemical substances which are used
to increase the fertility of soil are called
chemical fertilizers. They are rich in
minerals that are essential for the growth
and development of plants.
Chemical fertilizers are prepared by 13.2 Fig.
using different chemicals or minerals. Fig.
Prolonged use of chemical fertilizers Chemical fertilizer
affects the fertility and quality of soil.
Therefore, over use of chemical fertilizers
should be avoided.
Green plants mainly require three types of chemicals, viz nitrogen (N), phosphorus (P)
and potassium (K). So chemical fertilizers are prepared by using nitrogen, phosphorus
and potassium.
On the basis of presence of minerals, Do You Know
chemical fertilizers are of three types. They
are: The fertilizer containing nitrogen,
phosphorus and potassium is called NPK
i. Nitrogenous fertilizers fertilizer. It is called a complete fertilizer.
ii. Phosphorus fertilizers
iii. Potassium fertilizers
i. Nitrogenous fertilizers
The chemical fertilizers rich in nitrogen are called
nitrogenous fertilizers. They help in growth of
plants. They help in growth and development of
flowers, fruits and seeds. Urea (NH2 – CO – NH2),
ammonium chloride (NH4Cl), ammonium sulphate
[(NH4)2SO4], are examples of nitrogeneous fertilizers.
Nitrogen is essential for plants to:
i. help in fast growth of plants. 13.3
ii. synthesize chlorophyll.
GREEN Science (Chemistry) Book-9 247
iii. increase productivity of crops, fruits and vegetables.
iv. increase the amount of protein and protoplasm.
Due to deficiency of nitrogen in soil, plants become pale, flowers do not bloom properly, fruits
and seeds become small.
ii. Phosphorus fertilizers Fig. Fig.13.4
The chemical fertilizers rich in phosphorus
are called phosphorus fertilizers. Ammonium
phosphate [(NH4)3PO4], calcium super phosphate
[Ca(H2PO4)2CaSO4], bone meal, etc. are examples
of phosphorus fertilizers. These fertilizers help
in growth of roots, leaves and buds, ripening of
fruits and development of seeds. Due to deficiency
of phosphorus, roots of plants cannot develop and
cell division becomes passive.
iii. Potassium fertilizers 13.5
The chemical fertilizers rich in potassium are
called potassium fertilizers. Potassium chloride
(KCl), potassium sulphate (K2SO4), Potassium
nitrate (KNO3), Potassium carbonate (K2CO3),
etc. Potassium fertilizers help in photosynthesis,
formation of protein and cell division. In the
absence of potassium in soil, the immunity of
plants decreases and leaves and buds of plants
wither.
Advantages of inorganic fertilizers
1. Inorganic fertilizers contain special types of nutrient elements essential for plants.
2. They dissolve in water. So, plants can absorb them easily along with water.
3. They can be stored and transported easily.
4. They increase the fertility of soil.
Disadvantages of inorganic fertilizers
1. Overuse of inorganic fertilizers pollutes the environment.
2. Long term use of inorganic fertilizers increases acidity or alkalinity of soil.
3. Long term use of chemical fertilizers degrade the quality of soil.
248 GREEN Science (Chemistry) Book-9
Differences between Inorganic fertilizers and organic fertilizers
Inorganic fertilizers Chemical fertilizers
1. They are obtained from chemical 1. They are obtained from dead and
substances or minerals. decaying parts of plants and animals.
2. They dissolve completely in water. 2. They do not dissolve completely in
water.
3. They contain special types of nutrients. 3. They do not contain special types of
nutrients.
4. They degrade the quality of soil. 4. They do not degrade the quality of soil.
Points to be considered while using chemical fertilizers
1. We should test acidity and alkalinity of soil before using chemical fertilizers.
2. We should not let chemical fertilizers reach the sources of water.
3. We should cover mouth and nose while using chemical fertilizers.
4. We should reduce the over use of chemical fertilizers.
5. We should store chemical fertilizers away from vicinity of children.
Impact of use of chemical fertilizers on environment
Though chemical fertilizers increase the productivity of crops, they also cause chemical
pollution. Overuse of chemical fertilizers has many negative impacts in the environment.
It pollutes soil, air and water. If the same chemical fertilizer is used continuously, the
fertility of the fertilizer present in the soil cannot be absorbed by plants, which is washed
by rain water. Ultimately the excess fertilizer reaches pond, river, sea, etc. It causes water
pollution. Aquatic plants grow well due to chemical fertilizers. They absorb the oxygen
present in water. It decreases oxygen content in water. As a result, aquatic animals like
fishes die due to lack of oxygen. When these animals decay in water, they also pollute the
water. It adversely affects water ecosystem.
Key Concepts
1. The substances which are added to the soil to increase the productivity is crops are
called fertilizers.
2. The organic manure produced by decaying various parts of plants and animal
wastes is called compost manure.
3. Compost manure is called an organic fertilizer because it is produced by decaying
parts of plants and animal wastes.
4. Organic fertilizers are of two types. They are green manure and compost manure.
5. The plants grown by using compost fertilizers grow well and produce good fruits.
6. The chemical substances which are used to increase the fertility of soil are called
chemical fertilizers.
7. Organic fertilizers are prepared by using dead and decaying parts of plants and
animals.
GREEN Science (Chemistry) Book-9 249
8. Green plants mainly require three types of chemicals, viz. nitrogen (N), phosphorus
(P) and potassium (K). So chemical fertilizers are prepared by using nitrogen,
phosphorus and potassium.
9. The chemical fertilizers rich in nitrogen are called nitrogenous fertilizers. They help
in growth of plants. They help in growth and development of flowers, fruits and
seeds.
10. The chemical fertilizers rich in phosphorus are called phosphorus fertilizers.
Ammonium phosphate, calcium super phosphate, bone meal, etc. are examples of
phosphorus fertilizers.
11. The chemical fertilizers rich in potassium are called potassium fertilizers. Potassium
chloride, potassium sulphate, etc. Potassium fertilizers help in photosynthesis,
formation of protein and cell division.
12. We should test acidity and alkalinity of soil before using chemical fertilizers.
Sequential General Exercise 1
1. Choose the best answer from the given alternatives.
a. Which of the following is the source of compost manure?
Plants Animals
Minerals Plants and animals
b. Which of the given fertilizers does not degrade the quality of soil?
Organic fertilizer Inorganic fertilizer
Nitrogeneous fertilizer Potassium fertilizer
c. Which of the following is called a complete fertilizer?
NPK fertilizer Organic fertilizer
Potassium fertilizer Inorganic fertilizer
d. Which of the given fertilizers is essential for growth and development of roots?
Potassium chloride Calcium super phosphate
Ammonium nitrate Potassium sulphate
250 GREEN Science (Chemistry) Book-9
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