1. Grade 7 Science
Solutions

2. Solutions… a review
A homogeneous mixture ie. they appear as ONE substance
Examples: tap water, vinegar, gold jewelry, etc.

3. Solutions have 2 parts: Solute Solvent
The substance that dissolves (found in less amounts)
Solvent
The substance in which the solute dissolves (found in the greatest amounts)

4. Dissolving...
To mix completely ie. the solute dissolves into the solvent.
Some substances are able to dissolve better than others.

5. The Particle Theory of Matter states that “there are attractive forces between the particles”.

6. In order to dissolve, the particles must be more strongly attracted to the particles of the solvent than to themselves. This means that the solute is soluble in that solvent.

7. If the particles of the solute are more attracted to their own particles than the solvent particles, dissolving does NOT occur. The solute is said to be insoluble in that solvent. (ie. Mechanical)

8. Soluble or Insoluble?
soluble
insoluble

9. Solvent or Not?
Some materials are good solvents for some solutes but not others. For example, oil is insoluble in water but soluble in gasoline.

10. States of Solutes and Solvents
Air
Solute: oxygen, carbon dioxide, other gases
Solvent: nitrogen
Gas
Gas

11. Soda
Solute: carbon dioxide
Solvent: water
Gas
Liquid

12. Vinegar
Solute: acetic acid
Solvent: water
Liquid
Liquid

13. Filtered Sea Water
Solute: Salt and other minerals
Solvent: Water
Solid
Liquid

14. Brass
Solute: zinc
Solvent: copper
Solid
Solid
**Alloy: Solutions made from two or more metals.

15. Rate of Dissolving…
Factors that affect the rate of dissolving include:
Size of the solute
Temperature
Pressure

16. Size of Solute
The smaller the solute particles, the quicker they will dissolve
faster

17. Temperature
The higher the temperature, the more solute and the faster the solute will dissolve
faster

18. Pressure
Gases are more soluble in liquids under higher pressure (see page 267)
Opened bottle decreases pressure and “bubbles” come out of solution

19. Separation Techniques
Mechanical Sorting:
Used to separate the parts of a mixture based on properties such as particle size.
Examples: floatation & magnetism

20. magnetism
floatation

21. Filtration:
A common way to separate solid particles from a mixture
The filters can have holes of varying sizes… small to microscopic.

22. Oil filter
Coffee filter
Colander
Furnace filter

23. Evaporation:
Change of state from a liquid to a gas.
Used to recover a solid solute from a solution.

25. Distillation:
Uses two changes of state: evaporation and condensation.
It allows you to recover BOTH the solute and solvent from a solution.

26. Condensation
Evaporation

27. Paper Chromatography:
Used to separate the colored substances in a mixture such as ink.
Used to separate the solvents in a mixture.

28. Separation Techniques in the Home:
Colanders
Clothes dryers
Window screens
Coffee percolators
Salad spinners
Any others?

29. Distillation: A Review
A method of separation that allows you to recover a single solute and a single solvent.
The mixture must boil so that the solvent can evaporate and then cooled so that it can condense back into a liquid.

30. Distillation Apparatus
Evaporation
Condensation
Boil

31. Types of Distillations:
Simple Distillation
Separates a single solute from its solvent.

32. Fractional Distillation
Separates a mixture of liquids based on their varying boiling points.