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ResourcesChapter menu

Chapter 2Chemistry of Life

Revised by

R. LeBlanc

Section 1 Composition of MatterChapter 2

Matter

• Matter is anything that occupies space and has mass.

• Mass is the quantity of matter an object has.

Chapter 2

Matter

Section 1 Composition of Matter

Elements and Atoms

• Elements are made of a single kind of atom and cannot be broken down by chemical means into simpler substances.

• Atoms are composed of protons, neutrons, and electrons.

• Where are elements listed? In what order are the elements listed?

Chapter 2

Element

Elements and Atoms, continued

• The Nucleus– Protons and neutrons make up the nucleus of the

• Electrons– Electrons move about

the nucleus in orbitals.– An orbital is a three-

dimensional region around a nucleus that indicates the probable location of an electron.

• Isotopes

– Atoms of the same element that have a different number of neutrons are called isotopes.

Compounds

• Compounds consist of atoms of two or more elements that are joined by chemical bonds in a fixed proportion.

Chapter 2

Compounds

Compounds, continued

• Ionic Bonds– An ionic bond is formed when one atom gives up

an electron to another. The positive ion is then attracted to a negative ion to form the ionic bond.

Chapter 2

Ionic Bonding

Chapter 2

Ionic Bonding

Compounds, continued

• Covalent Bonds– A covalent bond is

formed when two atoms share electrons.

Chapter 2

Covalent Bonding

Section 2 EnergyChapter 2

Objectives

• Describe the physical properties of each state of matter.

• Describe the role of reactants and products in chemical reactions.

• Explain the relationship between enzymes and activation energy.

• Explain how oxidation and reduction reactions are linked.

Energy and Matter

• States of Matter– Addition of energy

to a substance can cause its state to change from a solid to a liquid and from a liquid to a gas.

Chapter 2

Energy

Section 2 Energy

Energy and Chemical Reactions

• Reactants are substances that enter chemical reactions.

• Products are substances produced by chemical reactions.

• Chemical Equation for Photosynthesis:

6CO2 + 6H2O C6H1206 + 6O2

Chapter 2

Energy and Chemical Reactions

Section 2 Energy

Energy and Chemical Reactions, continued

• Activation Energy– Enzymes lower the amount of activation energy

necessary for a reaction to begin in living systems.

Chapter 2

Activation Energy and Chemical Reactions

Section 2 Energy

Photosynthesis

• Process of using carbon dioxide, water and energy to create glucose (food) for use by a plant

6CO2 + 6H2O + Energy = C6H12O6 +6O2

• What are the reactants in this reaction?• What are the products?

Energy and Chemical Reactions, continued

• Oxidation Reduction Reactions– A chemical reaction in which electrons are

exchanged between atoms is called an oxidation-reduction reaction.

Section 3 Water and SolutionsChapter 2

Objectives

• Describe the structure of a water molecule.

• Explain how water’s polar nature affects its ability to dissolve substances.

• Outline the relationship between hydrogen bonding and the different properties of water.

• Identify the roles of solutes and solvents in solutions.

• Differentiate between acids and bases.

Polarity

• Water is considered to be a polar molecule due to an uneven distribution of charge.

• The electrons in a water molecule are shared unevenly between hydrogen and oxygen.

Polarity, continued

• Solubility of Water– The polarity of water makes it effective at

dissolving other polar substances such as sugars, ionic compounds, and some proteins.

Solutions

• A solution consists of a solute dissolved in a solvent.

Salt dissolving in water

• Hydrogen bonds make water a good solvent.• Water molecules form shells around positive and

negative ions, eliminating their attraction for each other.

Salt dissolving in water

Hydrogen Bonding

• A hydrogen bond is the force of attraction between a hydrogen molecule with a partial positive charge and another atom or molecule with a partial or full negative charge.

Hydrogen Bonding, continued

• Cohesion and Adhesion– Cohesion is an attractive force that holds

molecules of a single substance together, such as water molecules.

– Adhesion is the attractive force between two particles of different substances, such as water molecules and glass molecules.

Chapter 2

Comparing Cohesion and Adhesion

Section 3 Water and Solutions

ResourcesChapter menu animation

Click to view animation.

How does water get to the leaves of trees hundreds of feet tall?

Cohesion and Adhesion in Transpiration• Woody walls in a plant called xylem.• Cohesion and adhesion cause capillary action.• Water meniscuses become more concave, increasing

the surface tension.• Water moves from the roots up to the leaves of a

• Temperature Moderation– Water has the ability to absorb a relatively large

amount of energy as heat and the ability to cool surfaces through evaporation.

• Density of Ice– Solid water is less dense than liquid water due to

the shape of the water molecule and hydrogen bonding.

Acids and Bases

• Ionization of Water

– Water ionizes into hydronium ions (H3O+) and hydroxide ions (OH–).

Acids and Bases, continued

• Acids– Acidic solutions contain more hydronium ions

than hydroxide ions.

• Bases– Basic solutions contain more hydroxide ions than

hydronium ions.

Chapter 2

• pH– Scientists have developed a scale for comparing

the relative concentrations of hydronium ions and hydroxide ions in a solution. This scale is called the pH scale, and it ranges from 0 to 14.

Chapter 2

The pH Scale

• Buffers– Buffers are chemicals that neutralize the effects

of adding small amounts of either an acid or a base to a solution.

Chapter 2

Multiple Choice

1. The way in which elements bond to form compounds depends on which of the following?

A. the model of the atom

B. the structural formula of the compound

C. the dissociation of the ions in the compound

D. the number and arrangement of electrons in the atoms of the elements

Standardized Test PrepChapter 2

Multiple Choice, continued

1. The way in which elements bond to form compounds depends on which of the following?

A. the model of the atom

B. the structural formula of the compound

C. the dissociation of the ions in the compound

D. the number and arrangement of electrons in the atoms of the elements

2. If an atom is made up of 6 protons, 7 neutrons, and 6 electrons, what is its atomic number?

3. The amount of energy needed for this chemical reaction to begin is shown by the line rising from the reactants. What is this energy called?

A. chemical energy

B. electrical energy

C. activation energy

D. mechanical energy

Chapter 2

The graph below shows the energy in a chemical reaction as the reaction progresses. Use the graph to answer the questions that follow.

Standardized Test Prep

3. The amount of energy needed for this chemical reaction to begin is shown by the line rising from the reactants. What is this energy called?

A. chemical energy

B. electrical energy

C. activation energy

D. mechanical energy

Chapter 2

4. Suppose that this reaction needs a catalyst to proceed. In the absence of a catalyst, the activation energy would be which of the following?

F. larger than what is shown

G. the same as what is shown

H. smaller than what is shown

J. not much different from what is shown

Chapter 2

4. Suppose that this reaction needs a catalyst to proceed. In the absence of a catalyst, the activation energy would be which of the following?

F. larger than what is shown

G. the same as what is shown

H. smaller than what is shown

J. not much different from what is shown

Chapter 2

5. What is an aqueous solution that contains more hydroxide ions than hydronium ions called?

A. a gas

B. a base

C. a solid

D. an acid

Chapter 2

5. What is an aqueous solution that contains more hydroxide ions than hydronium ions called?

A. a gas

B. a base

C. a solid

D. an acid

Chapter 2

6. Oxidation : loss :: reduction :

F. win

G. gain

H. take

J. forfeit

Chapter 2 Standardized Test Prep

6. Oxidation : loss :: reduction :

F. win

G. gain

H. take

J. forfeit

Chapter 2 Standardized Test Prep

Multiple Choice, continued7. The covalent bonds on the water

molecule depicted in the picture above has partial positive charges on the hydrogen atom and a partial negative charge on the oxygen atom. What do the partial positive and partial negative charges on this water molecule mean?

A. Water is an ion.

B. Water is a polar molecule.

C. Water needs a proton and two electrons to be stable.

D. Oxygen atoms and hydrogen atoms have opposite charges.

Chapter 2

The illustration below is a space-filling model of water. Use the model to answer the following question.

Multiple Choice, continued7. The covalent bonds on the water

molecule depicted in the picture above has partial positive charges on the hydrogen atom and a partial negative charge on the oxygen atom. What do the partial positive and partial negative charges on this water molecule mean?

A. Water is an ion.

B. Water is a polar molecule.

C. Water needs a proton and two electrons to be stable.

D. Oxygen atoms and hydrogen atoms have opposite charges.

Chapter 2

The illustration below is a space-filling model of water. Use the model to answer the following question.

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