Chemistry DE F INI T IONS
F4 DE F INI T IONS
Chemistry is a field of science that studies the structures, properties, compositions and interactions between matters. -pg4 Scientific investigation is a scientific method used in solving problems in science. -pg8 Scientific method is a systematic method used by scientists or researchers to solve problems related to science. -pg9 1 : I N T R O D U C T I O N O F C H E M I S T R T Y
2: M A T T E R A N D T H E A T O M I C S T R U C T U R E Matter is something that has mass and occupies space. -pg24 Melting point is the constant temperature when a substance changes from solid state to become liquid at a specific pressure. -PG26 Freezing point is the constant temperature when a substance changes from liquid state to become solid at a specific pressure. -PG26 Matter is made up of particles called atoms – PG30 Subatomic particles - particles found in an atom which is made up of protons, neutrons and electrons. -PG29 Electron - negatively-charged particles -PG30 Elements - consist of particles of atoms or molecules -PG26 Compounds are made up of molecules or ions. –PG26 Proton - positively-charged particles in the nucleus -PG30
2: M A T T E R A N D T H E A T O M I C S T R U C T U R E Proton number - Number of protons in the nucleus of an atom. -PG32 Nucleon number - Total number of protons and neutrons in the nucleus of an atom. -PG32 Electron arrangement shows the nucleus and electron arrangement of an atom. -PG35 atomic structure shows the number of protons and neutrons in the nucleus and electron arrangement of an atom. -PG35 Isotopes are atoms of the same element with the same number of protons but different number of neutrons. -PG37 Natural abundance is the percentage of isotopes present in a natural sample of element. -PG37 Valence shell - Outermost shell filled with electrons -PG35 Valence electrons - Electrons in the valence shell -PG35 Sublimation is the process by which molecules go directly from solid into the vapor or gas phase. (QR) Deposition is the process by which molecules go directly from the gas phase into the solid phase. (QR)
3: T H E M O L E C O N C E P T, C H E M I C A L F O R M U L A A N D E Q U A T I O N 1 mol of a substance contains 6.02 × 1023 particles that form the substance.-pg50 Avogadro constant, NA is used as the conversion factor between the number of moles and the number of particles. -pg50 Molar mass is the mass of one mole of substance. -pg52 Molar volume is the volume occupied by 1 mol of a gas. (22.4 dm^3 mol^–1 at STP or 24 dm^3 Mol^–1 at RTP) - pg54 Relative atomic mass, RAM of an element is the average mass of an atom of the element compared to 1/12 of the mass of one carbon-12 atom.-pg45 The relative molecular mass, RMM of a molecule is the average mass of the molecule compared to 1/12 of the mass of one carbon-12 atom. -pg45 The relative formula mass, RFM is the relative mass of an ionic substance -pg48 Mole is unit to measure the amount of substance. -pg49
3: T H E M O L E C O N C E P T, C H E M I C A L F O R M U L A A N D E Q U A T I O N Chemical formula is a representation of a chemical substance using alphabets to represent the atoms and subscript numbers to show the number of each type of atoms found in the elementary entities of the substance.-pg59 The empirical formula is the chemical formula that shows the simplest ratio of the number of atoms of each element in a compound. -pg60 Molecular formula is the chemical formula that shows the actual number of atoms of each element found in a molecule of a compound. -pg60 Ionic compounds are made up of cations (positively-charged ions) and anions (negatively-charged ions).-pg67 Stoichiometry is the quantitative study of the composition of substances involved in a chemical reaction. -pg72
4: T H E P E R I O D I C T A B L E O F E L E M E N T S Periodic Table of Elements is a form of systematic classification of elements in ascending order of proton numbers from left to right and from top to bottom.– pg82 Groups -The vertical columns in the Periodic Table of Elements.– pg 82 A similar condition occurred with chlorine, Cl, bromine, Br and iodine, I. The group consisting of these three elements was named triad.-pg80 Arrangement as the Law of Octaves-arranged seven elements in a row that found that the chemical and physical properties of the first element recurred at every eighth element. -pg80 Periods -The horizontal rows in the Periodic Table of Elements. -pg83 Group 18 consists of elements of helium, He, neon, Ne, argon, Ar, krypton, Kr, xenon, Xe, radon, Rn and oganesson, Og. Elements in Group 18 are known as noble gases or inert gases.. -pg 84 Group 1 is made up of lithium, Li, sodium, Na, potassium, K, rubidium, Rb, caesium, Cs and francium, Fr. Group 1 elements are also known as alkali metals. -pg87 Group 17 consists of fluorine, F, chlorine, Cl, bromine, Br, iodine, I, astatine, At and tennessine, Ts. Group 17 elements are known as halogens and exist as diatomic molecules. -pg92 Period 3 consists of elements sodium, Na, magnesium, Mg, aluminium, Al, silicon, Si, phosphorus, P, sulphur, S, chlorine, Cl, and argon , Ar . -pg96
4: T H E P E R I O D I C T A B L E O F E L E M E N T S Semi-metallic elements or metalloid elements are elements that have both the properties of metals and non-metals. -pg99 Transition elements are placed in Group 3 and 12 in the Periodic Table of Elements. -pg101 Transition metal are metals with high melting point and boiling point, hard, shiny surfaces, malleable and ductile.-pg101
5 : C H E M I C A L B O N D Chemical bonds are formed when electron transfer or electron sharing takes place. -pg110 Ionic bond is formed by the transfer of electrons between a metal atom and a non-metal atom. pg111 Covalent bonds are formed when non-metal atoms share their electrons to achieve a stable duplet or octet electron arrangement.-pg114 A single bond is formed when two atoms share a pair of electrons. - pg114 A double bond is formed when two atoms share two pairs of electrons.-pg115 A triple bond is formed when two atoms share three pairs of electrons. -pg115 Hydrogen bonds are attraction forces between hydrogen atom, H that has bonded with an atom of high electronegativity, such as nitrogen, N, oxygen, O or fluorine, F with nitrogen, N, oxygen, O or fluorine, F in another molecule.- pg117 Dative bond or coordinate bond is a type of covalent bond where the electron pair that is shared comes from one atom only. -pg120 Metallic bond - electrostatic attraction force between the sea of electrons and the positivelycharged metal ions. -pg121 Delocalised electron means electron that move freely and is not owned by any atom nor ion. - pg121 Sea of electron is formed when the valence shells of metal atoms overlap, resulting in electron delocalisation. -pg121
6 : A C I D, B A S E A N D S A L T Acid - Chemical substances ionise in water to produce hydrogenions, H+. -PG136 Base is a substance that reacts with acids to produce salt and water only. -PG137 Alkali - A base that is soluble in water . -PG137 Alkali - Chemical substances that ionise in water to produce hydroxide ions, OH–. PG-138 PH is a logarithmic measure of the concentration of hydrogen ions in an aqueous solution.-PG143 Strong acid is an acid that ionises completely in water to produce a high concentration of hydrogen ions. - PG149 Weak acid is an acid that ionises partially in water to produce low concentration of hydrogen ions, H+.-PG150 Strong alkali is an alkali that ionises completely in water to produce a high concentration of hydroxide ions, OH–.-PG150 Weak alkali is an alkali that ionises partially in water to produce a low concentration of hydroxide ions, OH. -PG151 Concentration of a solution is a measurement that shows the quantity of solute dissolved in a unit volume of solution, normally in 1 dm^3 solution. - PG158 Concentration in unit g dm^–3, is the mass of solute found in 1 dm^3 solution. -PG158 Concentration in unit mol dm^–3, is the number of moles of solute found in 1 dm^3 solution.This concentration is called molarity. -PG158
6 : A C I D, B A S E A N D S A L T Standard solution is a solution with known concentration. -PG162 Neutralisation is a reaction between an acid and an alkali (base) to produce salt and water only. -PG168 Titration method is a quantitative analysis method to determine the volume of acid needed to completely neutralise a given volume of alkali and vice versa.-170 The end point-The point in the titration at which the acid-base indicator changes colour . - 170 Salt is an ionic compound formed when the hydrogen ion, H+ from the acid is replaced with the metal ion or the ammonium ion, NH4 - PG175 Soluble salts are salts that dissolve in water at room temperature -PG179 Non-soluble salts are salts that do not dissolve at room temperature.-pg179 Continuous variation method is used to construct the ionic equation for the formation of insoluble salts. In this method, the volume of one solution, A is fixed, while solution B is added to the solution A by increasing the volume- pg186 Gas Tests -The process to identify a gas can be carried out by the gas test -pg191 Qualitative analysis of a salt is a technique used to identify the cation and anion present in a salt by analysing its physical and chemical properties. -pg197
7: R A T E O F R E A C T I O N Rate of reaction is the changes in the quantity of the reactant per unit time or the changes in the quantity of product per unit time. -PG221 Average rate of reaction is the average value for the rate of reaction that occurs in a particular time interval.- PG221 Instantaneous rate of reaction is the rate of reaction at a particular point of time.-PG222 Catalysts are chemical substances that alter the rate of chemical reactions without undergoing any chemical changes at the end of the reaction. -PG235 Effective collisions- the reactant particles have energy equal to or more than the activation energy and collide in the correct orientation.-PG243 Activation energy is like an energy barrier that needs to be overcomed before a reaction can take place. -PG243 Exothermic reactions - reactions that release heat energy to the surroundings. -PG246 Endothermic reactions - reactions that absorb heat energy from the surroundings. -PG246
8 : M A N U F A C T U R E D S U B S T A N C E S I N I N D U S T R Y Alloy is a mixture of two or more elements where the main element is a metal. -PG 254 Glass – is silica is heated together with other chemicals – pg260 Fused silica glass is made from silica (silicon dioxide, SiO2) without adding any other chemical. - pg260 Soda-lime glass is made from silica, SiO2, soda (sodium carbonate, Na2 ,CO3) and limestone (calcium carbonate, CaCO3). -pg261 Borosilicate glass is made from silica, SiO2, soda, Na2CO3, limestone, CaCO3, boron oxide, B2O3 and aluminium oxide, AlO3 - pg261 Lead crystal glass is made from silica, SiO2, soda, Na2CO3 And lead(II) oxide, PbO. -pg261 Ceramic is a solid made up of inorganic and non-metallic substances. -pg262 Traditional ceramics are made from clay such as kaolin, Al2O3 ,2SiO2 ,2H2O. – pg263 Advanced ceramics are made from inorganic compounds such as oxides, carbides and nitrides. -pg263 Composite material is a material made from combining two or more non-homogeneous substances, that is matrix substance and strengthening substance. -pg265
8 : M A N U F A C T U R E D S U B S T A N C E S I N I N D U S T R Y Reinforced concrete is produced when steel bars or wire mesh (strengthening substance) is immersed in concrete (matrix substance). - pg266 Optical fibre consists of three layers. The innermost layer is the core that is made up of silica glass fibres (strengthening substance). The core is encased in a second layer or cladding that is made up of glass or plastic (matrix substance).-pg267 Photochromic glass is formed when glass (matrix substance) is combined with silver chloride, AgCl and copper(I) chloride, CuCl (strengthening substance). -pg268 Superconductors such as yttrium barium copper oxide, YBCO ceramic is a composite material that has superconductivity properties other than alloys.-pg268
G L O S S A R Y Abrasion - Resistance towards surface friction that occurs in a structure. Acidic oxide - Oxide compound formed from the reaction between non-metals and oxygen. Antiseptic Chemical - substance used to kill or prevent the growth of bacteria. Aqueous solution - A solution which solvent is water. Atom - The smallest particle in an element that takes part in a reaction. Basic oxide - Oxide compound that is formed from the reaction between metals and oxygen. Boiling point - Constant temperature at which a substance changes from liquid to gas at a particular pressure. Chemical equation - A way of writing that describes a chemical reaction in the form of words or chemical formula. Chemotherapy - Treatment that involves the use of certain chemicals to treat and control certain diseases, especially cancer. Coefficient - The number in front of a chemical formula in a chemical equation. Colouring agent Natural of synthetic colouring substance that is added to enhance the final colour of processed food. Crystallisation - The process or forming crystals from a saturated solution Degree of dissociation - Mole ratio of reactants that has dissociated to products in 1 litre of solution. Delocalised electron - Electron that moves freely and is not owned by any atoms or ions.
G L O S S A R Y Disinfectant Germ - killing agent used to sterilise objects such as laboratory equipment. Duplet electron - Stable arrangement of two electrons in the valence shell. Electron - Negatively charged subatomic particle that orbits the nucleus of an atom. Electronegativity - The tendency of an atom to pull shared electrons towards itself in a covalent bond. Expansion coefficient - The change in particle size to temperature changes ratio. Fungicide - Chemical substance to retard or destroy fungi. Herbicide - Chemical substance to retard or destroy weeds Lewis structure - Diagram that shows the bonds between atoms in a molecule and the electron lone pairs in a molecule. Maglev - Train transportation system that uses magnets to levitate and propel trains. Metalloid - Element with metal and non-metal properties. Neutron - Neutral subatomic particle in the nucleus of an atom. Octet - electron Stable arrangement of eight electrons in the valence shell arrangement Pesticide - Poison that is used to kill pests. Pharmaceutical - Field related to medicine. Precipitate - Solid that does not dissolve in a solvent and deposited at the bottom. Preservative - Food additive that delays or prevents the growth and reproduction processes of microorganisms that spoil food.
G L O S S A R Y Proton - Positively charged subatomic particle in the nucleus of an atom. Reactant - Starting material in a chemical reaction. Reaction - pathway refers to a reaction coordinate diagram that shows the change of energy when a reaction occurs. Refractive index - The ratio of the speed of light in vacuum to the speed of light in a particular medium Saturated solution - Solution that contains maximum amount of solute and cannot dissolve any more solute at a particular temperature. Semiconductor - Substance that has electrical insulator and conductor properties. Solute - Substance that dissolves in a solvent. Stoichiometry - Study that is related to the quantity of substance involved in a chemical reaction. STP - Abbreviation for standard temperature and pressure, which is 0 °C and 1 atm respectively. Volatility - The property of a liquid that rapidly changes to vapour.
F5 DE F INI T IONS
1 : R E D O X R E A C T I O N Redox reaction is a chemical reaction where oxidation and reduction occur simultaneously. -PG4 Oxidation reaction takes place when a reactant gains oxygen.-PG5 Reduction reaction takes place when a reactant loses oxygen.-PG5 Oxidation reaction takes place when a reactant loses hydrogen.-PG5 Reduction reaction takes place when a reactant gains hydrogen.-PG5 Oxidation reaction takes place when a reactant loses electron.-PG6 Reduction reaction takes place when a reactant gains electron.-PG6 Oxidising agent is a substance that oxidises other substances and is reduced in a redox reaction.-PG11 Reducing agent is a substance that reduces other substances and is oxidised in a redox reaction.-PG11 Oxidation number or oxidation state is the charge of the elements in a compound if the transfer of electrons occurs in an atom to form chemical bonds with other atoms.-PG12 Displacement of metal is carried out by adding a metal into a salt solution of another metal. -PG16 Electropositivity is the tendency of atoms to release electrons to form cations.-PG17 Electrochemical series is a series of metal arrangements according to the standard electrode potential, E^0 in the order of most negative to most positive.-PG17
1 : R E D O X R E A C T I O N Electrode potential is the potential difference produced when an equilibrium is established between metal M and the aqueous solution containing metal Mn+ ions in a half-cell.-PG22 Standard electrode potential, E0 is also known as the standard reduction potential.- PG24 Anode are electrodes where oxidation occurs. In a voltaic cell, the negative terminal is also known as anode. -PG27 Cathodes are electrodes where reduction occurs. In a voltaic cell, the positive terminal is also known as cathode.-PG27 Simple chemical cell is process where two different metal plates are dipped into an electrolyte and connected with connecting wires and also known as voltaic cell or galvanic cell. -pg27 Electrolytes are substances that can conduct electricity in either the molten state or aqueous solution and undergo chemical changes. -pg31 Non-electrolytes are substances that cannot conduct electricity in all states.-pg31 Electrolysis is a process whereby compounds in the molten state or an aqueous solution decompose into their constituent elements by passing electricity through them.-pg34
1 : R E D O X R E A C T I O N Electroplating of metals through electrolysis is done by making the object being electroplated as the cathode, the electroplating metal as the anode, and an aqueous solution containing the ions of the electroplating metal as the electrolyte. -pg44 Extraction of Metals -The methods for extracting reactive metals are based on the position of the metal in the reactivity series of metal. -pg48 Rusting of iron is a metal corrosion that occurs to iron.-pg52 Corrosion of metal is a redox reaction where the metal is oxidised spontaneously when the metal atoms release electrons to form metal ions.-pg52 Sacrificial protection is used for corrosion protection for bridge pillars, ship hulls and underground pipes.-pg56
2: C A R B O N C O M P O U N D Carbon compounds are compounds that contain carbon as their constituent element. - PG64 Organic compounds - Compounds originating from living things that contain the carbon element bonded covalently with other elements such as hydrogen, nitrogen, Sulphur and phosphorus. - PG64 Inorganic compoundsCompounds originating from non-living materials such as oxides of carbon, carbonate compounds and cyanide compounds. -PG64 Organic food is grown without using pesticides, synthetic fertilisers and without genetic modification (GMO). -PG64 Hydrocarbon- Organic compounds containing only hydrogen and carbon.-PG65 Non Hydrocarbon -Organic compounds containing carbon and hydrogen and other elements, such as oxygen, nitrogen, phosphorus or halogens. -PG65 Saturated hydrocarbon - Hydrocarbons containing only single bonds between carbon atoms. -PG65 Unsaturated hydrocarbon - Hydrocarbons containing at least one double bond or triple bond between carbon atoms. – PG65 Petroleum is a mixture of simple or long-chain hydrocarbons. - PG66
2: C A R B O N C O M P O U N D Fractional distillation -The fractions of hydrocarbons in petroleum are separated at different temperatures according to the size of the hydrocarbons. - PG66 Cracking - Long chain hydrocarbons are cracked into smaller molecules at a high temperature using a catalyst. - PG66 Cracking is the process of breaking long chain hydrocarbons into smaller hydrocarbons. -PG68 Homologous series - groups of compounds that classified according to their physical properties and chemical reactions of organic compounds. -PG71 Molecular formula is a chemical formula that shows the type and actual number of atoms of each element in a molecule.-PG72 Fermentation is the process in which yeast acts on carbohydrates (sugar or starch) to produce ethanol, C2H5OH and carbon dioxide, CO2 in the absence of oxygen, O2 -PG88 Structural isomerism is a phenomenon where a compound has the same molecular formula but with two or more different structural formulae. -PG101 Isomers are molecules that have the same molecular formula but different structural formulae. - PG101
3: T H E R M O C H E M I S T R Y Heat of reaction, ΔH is the heat change of one mole of reactant that reacts or one mole of product that is formed. -PG117 The Joule symbol J is the SI issued unit for energy, work and heat that is used in honour of James Prescott Joule (1818-1889). -PG120 Heat of precipitation is the heat change when 1 mole of precipitate is formed from their ions in an aqueous solution.-PG121 Heat of displacement is the heat change when one mole of a metal is displaced from its salt solution by a more electropositive metal – PG125 The heat of neutralisation is the heat change when one mole of water is formed from the reaction between an acid and an alkali. - PG127 Hydrochloric acid, HCl is a monoprotic acid.-PG130 Sulphuric acid, H2SO4 is a diprotic acid.- PG130 The heat of combustion is the heat released when 1 mole of a substance is completely burnt in excess oxygen, O2 -PG133 Fuels are substances that burn in the air to produce heat energy. – PG137 The fuel value of a fuel is the amount of heat energy released when one gram of fuel is completely burnt in excess oxygen. -PG137
4: P O L Y M E R A polymer is a long chain molecule that is made from a combination of many repeating basic units - PG144 Polymerisation reaction -The monomer combination reaction to produce a polymer -PG144 Monomer - The basic unit of a polymer. -PG144 Thermoplastic polymers are polymers that can be repeatedly remoulded upon heating and can be recycled. -PG145 Thermosetting polymers cannot be remoulded after heating. -PG145 Elastomer polymers can be stretched and can return to their original shape when released.- PG145 Addition polymerisation occurs when monomers that have double covalent bonds between two carbon atoms, C=C react with one another. -PG146 Condensation polymerisation - involves at least two different monomers. -PG147 Latex is a white fluid obtained from rubber trees when the tree bark is tapped. -PG151 Natural rubber that is found in latex is a natural polymer known as polyisoprene. -PG151 Vulcanisation is a process of producing rubber that is more elastic and with better quality through the production of crosslinks between polymer chains. - PG156 Synthetic rubber is a synthetic polymer that is elastic in nature or elastomer polymer. -PG159
5: C O N S U M E R A N D I N D U S T R I A L C H E M I S T R Y Oils and fats are esters produced through the reaction between fatty acids and glycerol (propan-1,2,3- triol). -PG166 Soaps are sodium or potassium fatty acid salts. -PG169 Fatty acids are long-chain carboxylic acids. -PG169 R is an alkyl group containing at least 8 carbon atoms. – PG169 Detergents are non-soap cleaning agents. -PG170 Detergents are sodium salts of sulphonic acids. -PG170 triglycerides - Oils and fats are natural esters. -PG170 Food additives are natural or synthetic ingredients added to food to prevent damage or to improve the appearance, taste or texture. -PG177 Medicines are chemicals used to help with the treatment or prevention of diseases. -PG181 Cosmetics are materials or products that are used externally to cleanse, protect or enhance one’s appearances. - pg184 Nanoscience is a study on processing of substances at nanoscale that are between 1 nanometre to 100 nanometres. – pg187 Nanotechnology is a development of substances or gadgets using the properties of nanoparticles. - pg187 Graphene is an extraordinary material with various distinctive characteristics that can be attributed to its physical properties. -pg189
5: C O N S U M E R A N D I N D U S T R I A L C H E M I S T R Y Green Technology is a technology or application developed to minimise the negative effects of harmful human activities. -pg191 Malaysia Green Technology and Climate Change Centre, which is also known as GreenTech Malaysia, is a government agency responsible for initiating various programmes and incentives to encourage the adoption of Green Technology in various economic sectors in Malaysia. -pg191 Green Technology is utilised in waste and wastewater management with the aim of ensuring more efficient waste management, reduction in greenhouse gases emission and removal of cleaner wastewater.- pg192 Wastewater is a liquid waste that consists of human waste ,food waste, oil and chemicals .Wastewater can be divided into domestic wastewater, stormwater runoff and industrial wastewater. - pg192
G L O S S A R Y Addition reaction – A chemical reaction that occurs when another atom is added to each carbon atom at the double bond --C=C-- to form a single covalent bond - -C-C-- . Anode – The electrode where the oxidation reaction takes place. Cathode – An electrode where reduction occurs. Cell notation – Shorthand representation of a chemical cell with the anode on the left and the cathode on the right is separated by two vertical lines representing a salt bridge or porous pot. Cracking –The process whereby long chain hydrocarbons are broken down into smaller molecules at high temperatures in the presence of a catalyst. Daniell cell – Chemical cell consists of zinc, Zn metal electrodes and copper, Cu metal electrodes dipped into their respective ionic salt solutions. Electrochemical Series – A series of metal arrangement in the order of standard electrode capacity, E^0 from the most negative to the most positive. Electrolysis – A process of decomposition of a compound in a molten state or an aqueous solution to its constituent elements when electric current is passed through it. Electrolyte – A substance in a molten state or an aqueous solution that can conduct electric currents and undergo chemical changes.
GLOSSARY E l e c t r o p l a t i n g – T h e e l e c t r o l y s i s p r o c e s s o f c o a t i n g t h e s u r fa c e o f a m e t a l w i t h t h i n a n d e v e n l a y e r o f a n o t h e r m e t a l . E s t e r i fi c a t i o n – T h e r e a c t i o n o f a l c o h o l w i t h c a r b o x y l i c a c i d t o p r o d u c e e s t e r a n d w a t e r . F u n c t i o n a l g r o u p – A g r o u p o f a t o m s b o n d e d t o a m o l e c u l e o f a n o r g a n i c c o m p o u n d t h a t d e t e r m i n e s t h e c h e m i c a l p r o p e r t i e s o f h o m o l o g o u s s e r i e s G a l v a n i s a t i o n – T h e p r o c e s s o f c o a t i n g o f i r o n w i t h a l a y e r o f z i n c s o t h a t i t i s r e s i s t a n t t o c o r r o s i o n . G e n e r a l fo r m u l a – T h e fo r m u l a t h a t s h o w s t h e g e n e r a l fo r m o f t h e m o l e c u l a r fo r m u l a o f a h o m o l o g o u s s e r i e s . G l y c e r o l – A n a l c o h o l t h a t c o n s i s t s o f t h r e e c a r b o n a t o m s a n d t h r e e h y d r o x y l g r o u p s . G r e e n T e c h n o l o g y – a t e c h n o l o g y o r a p p l i c a t i o n d e v e l o p e d t o m i n i m i s e t h e n e g a t i v e e ffe c t s o f h u m a n a c t i v i t i e s . H a r d w a t e r – W a t e r t h a t c o n t a i n s c a l c i u m , i o n s , C a 2 + o r m a g n e s i u m i o n s , M g 2 + t h a t d i s s o l v e i n i t .