Name Class Date

Chemistry of Life

Study Guide A

Answer Key

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Holt McDougal Biology ii Chemistry of Life

Study Guide A

Name Class Date

Section 1. ATOMS, IONS, AND MOLECULES

1. nucleus: dense center of an atom

2. neutron: particle with no electrical charge

3. proton: particle with positive electrical charge

4. electron: particle with negative electrical charge

5. compounds

6. elements

7. false

8. false

9. true

10. true

11. outermost

12. strong

13. electrons

14. covalent

15. compound

16. element

17. ionic bond

18. covalent bond

19. atom

20. molecule

Section 2. PROPERTIES OF WATER

1. false

2. true

3. true

4. a

5. b

6. c

7. evenly

8. solvent

9. nonpolar

10. more acidic, neutral, more basic

11. solute


Section 3. CARBON-BASED MOLECULES

1. true

2. false

3. true

4. false

5. Students should sketch one of the following, based on Figure 3.1 in the student text: straight chain, branched chain, or ring.

6. Provide energy

7. starches, sugar

8. Store energy

9. fat, oils

10. source of amino acids

11. beans, meat, nuts

12. map for making proteins

13. DNA, RNA

14. polymer

Section 4. CHEMICAL REACTIONS

1. reactants, products; reactants, products

2. chemical bonds

3. reactants

4. atoms

5. same rate

6. false

7. true

8. true

9. false

10. false

11. chemical reaction that absorbs more energy than it releases

12. chemical reaction that releases more energy than it absorbs

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

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Holt McDougal Biology ii Chemistry of Life

Study Guide A

Name Class Date


Study Guide A continued

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Holt McDougal Biology ii Chemistry of Life

Study Guide A

Name Class Date

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

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Holt McDougal Biology ii Chemistry of Life

Study Guide A

Name Class Date

Section 1: Atoms, Ions, and Molecules

Study Guide A

Key Concept

All living things are based on atoms and their interactions.

Vocabulary

atom / ion / molecule
element / ionic bond
compound / covalent bond

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
protons / electrons.

14. A molecule is held together by ionic / covalent bonds.

Vocabulary Check

element / compound / ion / molecule
ionic bond / covalent bond / atom

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

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Holt McDougal Biology 2 Chemistry of Life

Study Guide A Section 1: Atoms, Ions, and Molecules

Name Class Date


Section 2: Properties of Water

Study Guide A

Key Concept

Water’s unique properties allow life to exist on Earth.

Vocabulary

hydrogen bond / solution / acid
cohesion / solvent / base
adhesion / solute / pH

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?

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.

Vocabulary Check

Fill in the blank with either solvent or solute.

11. A ______dissolves in a solution.

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Holt McDougal Biology 3 Chemistry of Life

Study Guide A Section 2: Properties of Water

Name Class Date

Section 3: Carbon-Based Molecules

Study Guide A

Key Concept

Carbon-based molecules are the foundation of life.

Vocabulary

monomer / lipid / amino acid
polymer / fatty acid / nucleic acid
carbohydrate / protein

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.

5. Choose one of the three basic structures of carbon-based molecules to sketch in the space below. Label your sketch with the name of the basic structure.


Study Guide A continued

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.
Protein / 10. / 11.
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? ______

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Holt McDougal Biology 6 Chemistry of Life

Study Guide A Section 3: Carbon-Based Molecules

Name Class Date

Section 4: Chemical Reactions

Study Guide A

Key Concept

Life depends on chemical reactions.

Vocabulary

chemical reaction / bond energy / exothermic
reactant / equilibrium / endothermic
product / activation energy

Main Idea: Bonds break and form during chemical reactions.

1. Label the reactants and products in the chemical reactions shown below.

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.


Study Guide A continued

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
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

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Holt McDougal Biology 8 Chemistry of Life

Study Guide A Section 4: Chemical Reactions

Name Class Date

Section 5: Enzymes

Study Guide A

Key Concept

Enzymes are catalysts for chemical reactions in living things.

Vocabulary

catalyst / substrate
enzyme

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

Main idea: Enzymes allow chemical reactions to occur under tightly controlled conditions.

4. Take notes about enzymes by filling in the Main Idea Web below.

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 reaction.

6. Substrates are to catalysts / enzymes as keys are to locks.

7. Enzymes / substrates are catalysts for chemical reactions in living things.

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Holt McDougal Biology 10 Chemistry of Life

Study Guide A Section 5: Enzymes