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Name ______________________________ Class ___________________ Date __________________
Chemistry of Life
Study Guide A
Answer Key
SECTION 1. ATOMS, IONS, AND MOLECULES
SECTION 3. CARBON-BASED MOLECULES
1. nucleus: dense center of an atom
1. true
2. neutron: particle with no electrical charge
2. false
3. proton: particle with positive electrical charge
3. true
4. electron: particle with negative electrical charge
4. false
5. compounds
5. Students should sketch one of the following, based on
6. elements
Figure 3.1 in the student text: straight chain, branched
7. false
chain, or ring.
8. false
6. Provide energy
9. true
7. starches, sugar
10. true
8. Store energy
11. outermost
9. fat, oils
12. strong
10. source of amino acids
13. electrons
11. beans, meat, nuts
14. covalent
12.
15. compound
13. DNA, RNA
16. element
14. polymer
17. ionic bond
map for making proteins
SECTION 4. CHEMICAL REACTIONS
18. covalent bond
1. reactants, products; reactants, products
19. atom
2. chemical bonds
20. molecule
3. reactants
SECTION 2. PROPERTIES OF WATER
4. atoms
1. false
5. same rate
2. true
6. false
3. true
7. true
4. a
8. true
5. b
9. false
6. c
10. false
7. evenly
11. chemical reaction that absorbs more energy than it
8. solvent
releases
9. nonpolar
12. chemical reaction that releases more energy than it
10. more acidic, neutral, more basic
absorbs
11. solute
13. amount of energy that needs to be absorbed for a
chemical reaction to start
14. substances changed during a chemical reaction
15. substances made by a chemical reaction
16. state reached when reactants and products are made at
the same rate
17. amount of energy that will break a bond between two
atoms
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
Study Guide A
i
Chemistry of Life
Name ______________________________ Class ___________________ Date __________________
Study Guide A continued
SECTION 5. ENZYMES
1. b
2. c
3. a
4. (starting in upper left box and moving clockwise) in
living things, temperature and pH, by speeding them
up, by binding to the enzyme, making it possible for
the reaction to take place
5. decrease
6. enzymes
7. Enzymes
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
Study Guide A
ii
Chemistry of Life
Name ______________________________ Class ___________________ Date __________________
Section 1: Atoms, Ions, and Molecules
Study Guide A
KEY CONCEPT
All living things are based on atoms and their interactions.
MAIN IDEA: Living things consist of atoms of different elements.
Draw lines to connect the parts of an atom with their descriptions.
1. nucleus
particle with a positive electrical charge
2. neutron
particle with a negative electrical charge
3. proton
particle with no electrical charge
4. electron
dense center of an atom
Circle the word or phrase that best completes the sentence.
5. Water (H2O) and carbon dioxide (CO2), are examples of
compounds / elements.
6. Elements / Compounds are made up of only one type of atom.
MAIN IDEA: Ions form when atoms gain or lose electrons.
Choose whether the statement is true or false.
7. true / false An atom becomes an ion when its number of protons changes.
8. true / false Some ions are positively charged, and some ions have no charge.
9. true / false The formation of an ion results in a full outermost energy level.
10.true / false Ions usually form when electrons are transferred from one
atom to another.
Study Guide A continued
MAIN IDEA: Atoms share pairs of electrons in covalent bonds.
Circle the word or phrase that best completes the sentence.
11. Shared pairs of electrons fill the innermost / outermost energy levels of
bonded atoms.
12. Covalent bonds are generally very strong / weak.
13. Two atoms may form several covalent bonds to share several pairs of
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
Study Guide A
1
Chemistry of Life
Section 1: Atoms, Ions, and Molecules
Name ______________________________ Class ___________________ Date __________________
protons / electrons.
14. A molecule is held together by ionic / covalent bonds.
Vocabulary Check
element
compound
ion
ionic bond
covalent bond
atom
molecule
Write each word or phrase next to its definition.
____________________ 15.
a substance made of atoms of different elements
bonded together in a certain ratio
____________________ 16.
a particular type of atom
____________________ 17.
a bond formed by the electrical force between two
ions of opposite charge
____________________ 18.
a bond formed when two atoms share a pair
of electrons
____________________ 19.
the smallest basic unit of matter
____________________ 20.
two or more atoms held together by covalent bonds
Section 2: Properties of Water
KEY CONCEPT
Water’s unique properties allow life to exist on Earth.
Main Idea: LIFE DEPENDS ON HYDROGEN BONDS IN WATER.
Choose whether the statement is true or false.
1. true / false Polar molecules have two regions with a slight positive charge.
2. true / false Water is a polar molecule.
3. true / false Slightly charged regions of water molecules form hydrogen bonds.
Choose the best answer for the question.
4. Which property allows water to resist changes in temperature?
a. high specific heat
b. cohesion
c. adhesion
d. polarity
5. Which property causes water to form beads?
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
Study Guide A
2
Chemistry of Life
Section 1: Atoms, Ions, and Molecules
Name ______________________________ Class ___________________ Date __________________
a. high specific heat
b. cohesion
c. adhesion
d. polarity
6. Which property of water helps plants to transport water from their roots to their leaves?
a. high specific heat
b. cohesion
c. adhesion
d. polarity
Study Guide A continued
MAIN IDEA: Many compounds dissolve in water.
Circle the word or phrase that best completes the sentence.
7. A solution is a mixture of substances that is evenly / unevenly distributed throughout the
entire mixture.
8. Blood plasma is an example of a solvent / solute.
9. “Oil and water don’t mix” because a polar / nonpolar molecule can’t easily dissolve in a
polar solvent.
MAIN IDEA: Some compounds form acids or bases.
10. In the pH table below, add labels to show which side of the table shows pHs that are
more acidic, and which side shows pHs that are more basic. Then add a label to show
which pH is neutral.
1
2
3
4
5
6
7
8
9
10 11
12
13
14
___________________________________________________________________
Vocabulary Check
Fill in the blank with either solvent or solute.
11. A __________ dissolves in a solution.
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
Study Guide A
3
Chemistry of Life
Section 2: Properties of Water
Name ______________________________ Class ___________________ Date __________________
Section 3: Carbon-Based Molecules
Study Guide A
MAIN IDEA: Carbon atoms have unique bonding properties.
Choose whether the statement is true or false.
1. true / false Carbon atoms form the building blocks of most living things.
2. true / false Carbon’s outer energy level is full.
3. true / false Carbon atoms can form covalent bonds with up to four other atoms.
4. true / false The three basic structures of carbon-based molecules are straight chain, bent
chain, and ring.
MAIN IDEA: Four main types of carbon-based molecules are found in living things.
Complete the table with the functions and examples provided for each type of
carbon-based molecule.
Functions
Examples
Provide energy
meat
fat
oils
Building blocks of proteins
sugar
beans
DNA
Map for making proteins
RNA
starches
nuts
Store energy
Molecule Type
Functions
Examples
Carbohydrate
6.
7.
Lipid
8.
9.
10.
11.
Protein
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
Study Guide A
4
Chemistry of Life
Section 5: Enzymes
Name ______________________________ Class ___________________ Date __________________
Nucleic acid
12.
13.
Vocabulary Check
14. The prefix mono- means “one,” and the prefix poly- means “many.”
Which contains more molecules, a monomer or a polymer? _____________________
Section 4: Chemical Reactions
KEY CONCEPT
Life depends on chemical reactions.
Circle the word or phrase that best completes the sentence.
2. During a chemical reaction, chemical bonds / solutes break and reform.
3. Reactants / products are the substances changed during a chemical reaction.
4. Bond energy is the amount of energy it takes to break a bond between two
atoms / ions.
5. Equilibrium occurs when reactants and products are made at the same rate / different
rates.
MAIN IDEA: Chemical reactions release or absorb energy.
Choose whether the statement is true or false.
6. true / false Not all chemical reactions involve changes in energy.
7. true / false Activation energy is required for a chemical reaction to start.
8. true / false Some chemical reactions release more energy than they absorb, while others
absorb more energy than they release.
9. true / false Chemical reactions can occur whether or not energy is added to the reactants.
10. true / false An exothermic chemical reaction absorbs more energy than it releases.
Vocabulary Check
Draw lines to connect the words or phrases that mean the same thing.
11. endothermic reaction
substances changed during a
chemical reaction
12. exothermic reaction
substances made by a chemical reaction
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
Study Guide A
5
Chemistry of Life
Section 5: Enzymes
Name ______________________________ Class ___________________ Date __________________
13. activation energy
chemical reaction that releases more energy
than it absorbs
14. reactants
chemical reaction that absorbs more energy
than it releases
15. products
amount of energy that needs to be absorbed
for a chemical reaction to start
16. equilibrium
amount of energy that will break a bond
between two atoms
17. bond energy
state reached when reactants and products are
made at the same rate
MAIN IDEA: A catalyst lowers activation energy.
Choose the best answer to the question.
1. Activation energy is the energy required to
a. complete a chemical reaction.
b. start a chemical reaction.
c. produce a catalyst.
d. produce the reactants.
2. Which of the following can reduce the amount of energy needed for a chemical reaction
to take place?
a. reactant
b. product
c. catalyst
d. hydrogen bond
3. What happens to the speed of a chemical reaction when a catalyst is present?
a. It speeds up.
b. It slows down.
c. It stays the same.
d. It becomes erratic.
Study Guide A continued
Vocabulary Check
Circle the word or phrase that best completes the sentence.
5. A catalyst can increase / decrease the amount of energy needed to start a chemical
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
Study Guide A
6
Chemistry of Life
Section 5: Enzymes
Name ______________________________ Class ___________________ Date __________________
reaction.
6. Substrates are to catalysts / enzymes as keys are to locks.
7. Enzymes / substrates are catalysts for chemical reactions in living things.
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
Study Guide A
7
Chemistry of Life
Section 5: Enzymes