1. Chapter 2 Chemistry of Life
Modern Biology Textbook
Holt

2. Objectives Chapter 2 Define the term matter.
Section 1 Composition of Matter
Chapter 2
Objectives
Define the term matter.
Explain the relationship between elements and atoms.
Draw and label a model of the structure of an atom.
Explain how compounds affect an atom’s stability.
Contrast covalent and ionic bonds.

3. Matter Chapter 2 Matter is anything that occupies space and has mass.
Section 1 Composition of Matter
Chapter 2
Matter
Matter is anything that occupies space and has mass.
Mass is the quantity of matter an object has.

4. Elements and Atoms Chapter 2
Section 1 Composition of Matter
Chapter 2
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.

5. Elements and Atoms, continued
Section 1 Composition of Matter
Chapter 2
Elements and Atoms, continued
The Nucleus
Protons and neutrons make up the nucleus of the atom.
Protons are positively charged particles.
Neutrons have no charge (neutral).
Together the mass of the protons and neutrons in the nucleus of an atom makes up the atom’s atomic mass.

6. Elements and Atoms, continued
Section 1 Composition of Matter
Chapter 2
Elements and Atoms, continued
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.

7. Elements and Atoms, continued
Section 1 Composition of Matter
Chapter 2
Elements and Atoms, continued
Isotopes
Atoms of the same element that have a different number of neutrons are called isotopes.

8. Section 1 Composition of Matter
Chapter 2
Compounds
Compounds consist of atoms of two or more elements that are joined by chemical bonds in a fixed proportion.

9. Chapter 2 Compounds, continued Covalent Bonds
Section 1 Composition of Matter
Chapter 2
Compounds, continued
Covalent Bonds
A covalent bond is formed when two atoms share electrons.

10. Chapter 2 Compounds, continued Ionic Bonds
Section 1 Composition of Matter
Chapter 2
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.

11. Section 1 Composition of Matter
Chapter 2
Ionic Bonding

12. Section 2 Energy
Chapter 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.

13. Chapter 2 Energy and Matter States of Matter
Section 2 Energy
Chapter 2
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.

14. Energy and Chemical Reactions
Section 2 Energy
Chapter 2
Energy and Chemical Reactions
Reactants are substances that enter chemical reactions.
Products are substances produced by chemical reactions.

15. Energy and Chemical Reactions
Section 2 Energy
Chapter 2
Energy and Chemical Reactions

16. Energy and Chemical Reactions, continued
Section 2 Energy
Chapter 2
Energy and Chemical Reactions, continued
Activation Energy
Enzymes lower the amount of activation energy necessary for a reaction to begin in living systems.
Oxidation Reduction Reactions
A chemical reaction in which electrons are exchanged between atoms is called an oxidation-reduction reaction.

17. Chapter 2 Objectives Describe the structure of a water molecule.
Section 3 Water and Solutions
Chapter 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.

18. Section 3 Water and Solutions
Chapter 2
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.

19. Chapter 2 Polarity, continued Solubility of Water
Section 3 Water and Solutions
Chapter 2
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.

20. Chapter 2 Hydrogen Bonding
Section 3 Water and Solutions
Chapter 2
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.

21. Hydrogen Bonding, continued
Section 3 Water and Solutions
Chapter 2
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.

22. Hydrogen Bonding, continued
Section 3 Water and Solutions
Chapter 2
Hydrogen Bonding, continued
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.

23. Section 3 Water and Solutions
Chapter 2
Solutions
A solution consists of a solute dissolved in a solvent.

24. Acids and Bases, continued
Section 3 Water and Solutions
Chapter 2
Acids and Bases, continued
Ionization of Water
Water ionizes into hydronium ions (H3O+) and hydroxide ions (OH–).
Acids
Acidic solutions contain more hydronium ions than hydroxide ions.

25. Acids and Bases, continued
Section 3 Water and Solutions
Chapter 2
Acids and Bases, continued
Bases
Basic solutions contain more hydroxide ions than hydronium ions.
Buffers
Buffers are chemicals that neutralize the effects of adding small amounts of either an acid or a base to a solution.

26. Acids and Bases, continued
Section 3 Water and Solutions
Chapter 2
Acids and Bases, continued 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.

27. Section 3 Water and Solutions
Chapter 2
The pH Scale