1. Chapter 2-3 Water and Solutions

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.

3. 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.
Solubility of Water
The polarity of water makes it effective at dissolving other polar substances such as sugars, ionic compounds, and some proteins

4. 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.

5. 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.
How might plants use these properties of water?

6. Surface Tension
The hydrogen bonds at the surface of water give water a surface temporarily like an elastic sheet.

7. Temperature moderation
High Heat Capacity
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.

8. Make a chart Property of water What does this mean?
Why is it important?
Cohesion
Adhesion
High Heat Capacity
Solvent

9. Solutions
A solution consists of a solute dissolved in a solvent.

10. Water loving or water hating?
Hydrophobic Substances do not mix with water
Hydrophillic Substances do mix with water.
Years ago they sprayed wetlands with oil to suffocate mosquito larvae. How would Oil affect the ability of plants and animals to float on the surface of the water?

11. Acids and Bases Ionization of Water Acids Bases
Water ionizes into hydronium ions (H3O+) and hydroxide ions (OH–).
Acids
Acidic solutions contain more hydronium ions than hydroxide ions.
Bases
Basic solutions contain more hydroxide ions than hydronium ions.

12. Acids and Bases ContinuedpH
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.
Buffers
Buffers are chemicals that neutralize the effects of adding small amounts of either an acid or a base to a solution.

14. Acid or a Base?
Lemon juice
Ammonia
Pop
Antacid
shampoo