1. Section 1 – pg 256 Understanding Solutions
Chapter 7
Section 1 – pg 256
Understanding Solutions

2. Pg 256
What is a Solution?
Solution: a uniform mixture that contains a solvent and at least one solute
Solvent: the part of a solution present in the largest amount; it dissolves the other substances
Solute: the substance that is present in the solution in a smaller amount and is dissolved by the solvents
A solution has the same properties throughout. It contains solute particles that are too small to see.
Pepper in water: not a solution
Sugar water: solution

3. Dissolving one substance in another is a physical change
Pg 256
Dissolving one substance in another is a physical change
Neither substances change into a new one
Each substance retains its original properties
Each substance can be recovered

4. Pg 256
Solutions in Water
Water is considered the “universal solvent” because everything (or close to it) dissolves in it
We dissolve sugar and carbon dioxide in water to make soda
Plants survive because nutrients in the soil dissolve in the water that the plant takes in
Water is the solvent in blood, saliva and tears

5. Solutions Without Water
Pg 257
Solutions Without Water
Many solutions are made with solvents other than water
Gasoline is a solution of several liquids
Some solutions do not have a liquid as its solvent
Air is a solution of many gases
Stainless steel is a solution of many solids

6. Pg 258
Colloids
Colloids: a mixture that contains small, undissolved particles that do not settle out
A colloid contains larger particles than a solution. The particles are still too small to be seen easily, but are large enough to scatter a light beam
Examples: milk, fog, gelatin, mayonnaise, shaving cream, whipping cream

7. Pg 258
Suspensions
Suspension: a mixture in which particles can be seen and easily separated by settling or filtration
A suspension does not have the same properties throughout. It contains visible particles that are larger than the particles in solutions or colloids
Examples: pepper in water, snow globes

8. Particles in a Solution
Pg 259
Particles in a Solution
When a solution forms, particles of the solvent surround and separate the particles of the solute

9. Ionic and Molecular Compounds in Solution
Ionic Compounds in a water solution
The ions break apart and are attracted to the polar water molecules
Molecular compound in water
Break up into individual neutral molecules
The molecules move away from one another but the covalent bonds do not break
Pg 259

10. Effects of Solutes on Solvents
Pg 260
Effects of Solutes on Solvents
Solutes lower the freezing point and raise the boiling point of a solvent

11. Lowering Freezing Points
Pg 260
Lowering Freezing Points
Pure water has molecules that freeze (turn solid) at 0 degrees Celsius
When water freezes, water molecules join together to form crystals of solid ice
Solute particles make it harder for the crystals to form therefore the temperature must drop lower than 0oC for the solution to freeze
This is why people put salt on the sidewalks in places that get cold temperatures

12. Higher Boiling Point Pg 261
The water molecules need more energy to escape when a solute is present
Solutes raise the boiling temperature, therefore the solution must be heated higher for molecules to escape
Adding salt to water decreases cooking time because the water is hotter
Car radiators use a solution of water and another liquid (antifreeze) which can absorb more heat given off by the engine and also not freeze in cold conditions

13. Chapter 7 Section 1 Homework – pg 261

14. 1A. What is a solution?

15. 1B. How are solutions different from colloids and suspensions?

16. 1C. Suppose you mix food coloring in water to make it blue
1C. Suppose you mix food coloring in water to make it blue. Have you made a solution or a suspension? Explain.

17. 2A. What happens to the solute particles when a solution forms?

18. 2B. Describe as a series of steps how table salt in water makes a solution that can conduct electricity

19. 3A. What effects do solutes have on a solvent’s freezing and boiling points?

20. 3B. Why is the temperature needed to freeze ocean water lower than the temp. needed to freeze the surface of a freshwater lake?

21. 3C. Why does salt sprinkled on icy roads cause the ice to melt?