Solving Problems_ A Chemistry Handbook

CHAPTER 23 SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK

Photosynthesis and Respiration Sunlight is the source of▲▲
energy for nearly all living things. During the process of photosyn-
thesis, plants, algae, and some kinds of bacteria use the energy in
sunlight to build carbohydrate molecules from carbon dioxide and
water. Animals and some other organisms cannot photosynthesize.
They take in carbohydrates by eating plants or other animals. The
net chemical equation for the photosynthesis of glucose follows.

6CO2 ϩ 6H2O ϩ light energy 0 C6H12O6 ϩ 6O2

Carbon Water Glucose Oxygen
dioxide

Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. Later, the carbohydrates that were produced during photosynthesis
are broken down in a set of catabolic reactions known as cellular
respiration, releasing energy for life processes. The net equation for
cellular respiration of glucose is the opposite of the equation for
photosynthesis.

C6H12O6 ϩ 6O2 0 6CO2 ϩ 6H2O ϩ energy

Glucose Oxygen Carbon Water
dioxide

Fermentation When oxygen is absent or in short supply, some
cells—such as yeast, some bacteria, and the muscle cells in your
body—can break down glucose without oxygen in a process called
fermentation. During fermentation, glucose is broken down and a
small amount of energy is released. There are two common forms of
fermentation. In alcoholic fermentation, ethanol and carbon dioxide
are produced. Lactic acid fermentation produces lactic acid.

Solving Problems: A Chemistry Handbook Chemistry: Matter and Change 243

CHAPTER 23 SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK

Practice Problems

Copy the following table on a sheet of paper. Then complete it
by placing a check mark in the appropriate columns.

Photosynthesis Cellular Fermentation
Respiration

22. Releases energy
23. Uses energy
24. Produces glucose
25. Breaks down

glucose
26. Produces oxygen
27. Uses oxygen
28. Catabolic process
29. Anabolic process

Chapter 23 Review Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.

30. What effect do enzymes have on the chemical reactions that
take place in living things? Why are enzymes necessary for
life?

31. Corn syrup is made by breaking down cornstarch chemically.
What monosaccharide would be most abundant in corn syrup?
Explain your answer.

32. What four molecules would you expect to get from the break-
down of a triglyceride?

33. What is the function of DNA in the activities of a cell?

34. Your cells carry out cellular respiration. What is the function of
this process? What process is the reverse of cellular respiration?

244 Chemistry: Matter and Change Solving Problems: A Chemistry Handbook

CHAPTER 24 SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK

Nuclear Chemistry

Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. ▲24.1 Nuclear Radiation

In 1895, William Roentgen found that certain materials emit invisi-
ble rays when bombarded with electrons. He named these emissions
X rays. Around the same time, Henri Becquerel was studying miner-
als that give off light after being exposed to sunlight—a process
called phosphorescence. While trying to determine whether phos-
phorescent minerals also emit X rays, Becquerel found that
phosphorescent uranium salts emit rays that darken photographic
plates, even if they are not first exposed to sunlight. Subsequently,
Marie Curie and her husband, Pierre, discovered that the darkening
of the photographic plates was due to rays emitted from the uranium
atoms themselves.

Marie Curie named the process by which materials emit rays
radioactivity. The rays and particles that are emitted by radioactive
materials are called radiation. Marie and Pierre Curie’s work helped
establish the field of nuclear chemistry.

Types of radiation Isotopes of atoms with unstable nuclei are
called radioisotopes. An unstable nucleus emits radiation to become
more stable—a process called radioactive decay. Radioisotopes emit
various types of radiation, including alpha particles (␣), beta parti-
cles (␤), and gamma (␥) rays.

Alpha radiation is a stream of alpha particles (helium nuclei).
The equations below describe what happens when radium-226
(whose nucleus contains 88 protons and 138 neutrons) emits an
alpha particle.

22886Ra 0 28262Rn ϩ 24He

Radium-226 0 Radon-222 ϩ Alpha particle

Notice that the sum of the mass numbers (superscripts) and the sum
of the atomic numbers (subscripts) on each side of the arrow are
equal, that is, the particles are balanced. When a radioactive nucleus
undergoes alpha decay, the resulting nucleus has an atomic number
that is lower by 2 and a mass number that is lower by 4. The change
in atomic number changes the identity of the element.

Solving Problems: A Chemistry Handbook Chemistry: Matter and Change 245