Chapter 2 Chemistry of Life

1. Chapter 2Chemistry of Life Modern Biology Textbook Holt

2. 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 howcompounds affect an atom’s stability. • Contrast covalent and ionic bonds.

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

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

15. Section 2 Energy Chapter 2 Energy and Chemical Reactions

16. 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. 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. 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. 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. 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. 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. 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. 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. 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