1. Matter can be classified as mixtures or pure substances
Grade 7 Science
Unit 3:
Mixtures & Solutions
Chapter 7
Matter can be classified as mixtures or pure substances

2. Particle Theory of Matter
All matter is made up of tiny particles.
These particles are always moving… they have energy.
There are spaces among particles.
There are attractive forces between the particles.
The particles of one substance differ from the particles of other substances.

3. How mixtures are different from pure substances
7.1
Page 230
How mixtures are different from pure substances

4. Pure substances Mixtures
Matter can be either:
Pure substances
Mixtures
Mixtures are the physical combination of two or more pure substances.
Contain only one kind of particle and are the same throughout.

5. Pure Substances...p.236 ALWAYS appear as uniform throughout
They contain either:
Only one type of particle
Gold and Oxygen.
Two or more particles chemically combined to form a different substance.
Water is H²O which is hydrogen's and 1 oxygen

6. Pure Substance
Substances don’t usually occur in their pure form in nature, so in order to obtain pure substances, people must refine raw materials.
Bauxite
makes
Aluminum foil

7. Examples of Pure Substances
sugar (C12H22O11)
copper (Cu)
distilled water (H2O)
carbon dioxide (CO2)
oxygen (O2)
NOTE: pure substances
covered are not limited to elements.

9. Mixtures
They are the physical combination of two or more pure substances. ? + =
Water
Sugar

10. Mixtures p.232 MAY have distinct visible components.
MAY appear uniform throughout.

11. Six of the possible kinds of mixtures are:
a mixture of gases
a mixture of liquids
a mixture of gases in a liquid
a mixture of solids
a mixture of solids in a liquid
a mixture of solids and gases

12. Soft drinks are mixtures made from:
- liquid water
Solid sugar
Carbon dioxide gas

13. Commonly used mixtures
Detergents
Cleaners
Formed by adding water to the cleaner
Gasoline – oil mixtures
Lawn mower engines require specific amounts of oil to be mixed with gas

14. Examples of Mixtures… kool-aid chocolate chip cookie concrete
salad dressing
Air
Bread

15. For each picture find the arrow and state the kind of mixture.
Ex: mixture of gases in a liquid

16. Apply: The particle theory of matter
#1: All matter is made up of tiny particles.
#5: The particles of one substance differ from the particles of other substances.
1 type of particle

17. In class activity T r u e F a l s e 1. Air is a mixture. _____
2. Gold is a pure substance. _____
3. Water from a lake is a pure substance. _____
4. A pure substance contains particles that are all alike. _____
5. Two different gases together make up a mixture. _____
Work book:
Page 1 – 3

18. p. 235
Heterogeneous and homogeneous
Mixtures

20. What is a mechanical Mixture?
Mixtures composed of two or more substances that remain visible even after they are mixed.
Sometimes need a microscope (see p. 245)
Can be solid, liquid or gas
The particles do not evenly mix

21. Mechanical mixtures are also known as heterogeneous mixtures (uneven mixtures).
A salad dressing made of oil and vinegar is considered a heterogeneous mixture because its components:
oil and vinegar — remain separate and distinct.
Think about a chocolate chip cookie.
Would it be considered a mechanical mixture?
Why or why not?
________________________________
p.244

22. Heterogeneous Mixtures
Example:
Smog-filled air
the amount of smog is not uniform inside the air.
Granola cereal or trail mix
the individual ingredients such as raisins, nuts, and dried fruit remain visible even after mixing.
Concrete
the components of the sand, lime, and water used to create it often remain visible.

23. Heterogeneous Mixtures
Granola bar

24. What is a Solution?
A type of mixture in which the pure substances within the solution mix together so well that they give the appearance of only one substance.
Solutions can be any combination of the three states of matter— solid, liquid, and gas.
Particles appear to be mixed evenly and to be the same throughout.

25. Solutions are also called Homogeneous mixtures
p.243
Solutions are also called Homogeneous mixtures
Examples:
When sugar is mixed with water, the sugar seems to "disappear." Yet, if you were to taste the mixture, you would know the sugar was still there. Also, if you were to place the solution in a shallow dish and allow the water to evaporate, the sugar would reappear.
Air - dissolve carbon dioxide, oxygen, and argon into nitrogen gas.
Brass- made up of copper and zinc.

26. Homogeneous Mixture Stainless steel Kool-aid
The particles are evenly mixed so that none of the original substances are visible.
Stainless steel
Kool-aid

27. Mixtures can be classified into 2 types:p.234
Heterogeneous
A non-uniform mixing
Particles create layers or parts
May also appear as one substance
Light will scatter as it passes through
May or may not need a microscope to see parts
Homogeneous
A uniform mixing
Appear as one substance
Particles are evenly spread out
Light will pass through unaffected
Cannot see parts with a microscope

28. Illustrating the particle theory of matter.
Mechanical mixture
Solution

29. In class work p. 235 Questions 1 – 3 p. 237 Questions 1 – 3
Workbook
In class work

30. Combination of mixtures p. 244
Sometimes you cannot tell whether something is homogeneous or heterogeneous just by looking at it.
The mixtures are hard to classify:
Homogeneous
Heterogeneous
However, we can use light
to determine…

31. Using light: homogeneous and heterogeneous

32. Homogeneous Mixture They appear to be ONE substance
light passes through unaffected

33. Heterogeneous Mixtures
Light will scatter because it reflects off the particles

34. Heterogeneous mixtures
Tyndall Effect…
Homogeneous mixture
Heterogeneous mixtures
copper (II) sulfate solution
salt water
sugar water
vegetable oil and water
Pepper and water
sugar & vegetable oil
vinegar and salad oil

35. Is it homogeneous or heterogeneous? Or a combination?
A large number of mixtures are not classified as either homogeneous or heterogeneous but rather are combinations of both.
They fall on a continuum from homogeneous to heterogeneous depending on particle size…
Combination of both

36. Some mixtures are combinations of heterogeneous and homogeneous mixtures
Milk
Orange juice
Soft drink
Ex: Orange juice:
Homogeneous: sugars with water
Heterogeneous: is a combination of solid orange pulp and water.

37. In class activity
Name one example of a heterogeneous mixture and one example of a homogeneous mixture.
Explain how you are able to tell the two types of mixtures apart.
Chapter review p.250 Questions 1-10
p. 245 Questions 1-4
p. 249 Questions 1-6
Workbook