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Unit 3: Mixtures & Solutions:

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1 Unit 3: Mixtures & Solutions:
Grade 7 Science Unit 3: Mixtures & Solutions:

2 Particle Theory of Matter
1. All matter is made up of tiny particles. 2. These particles are always moving… they have energy. 3. There are spaces among particles. 4. There are attractive forces between the particles. 5. The particles of one substance differ from the particles of other substances.

3 We can classify matter as: a pure substance or as a mixture.
Classifying Matter We can classify matter as: a pure substance or as a mixture.

4 Mixtures + = Sugar Water
Mixtures contain two or more different kinds of particles. MAY appear the same throughout MAY have distinct visible parts + = Sugar and water Sugar Water

5 Examples of Mixtures… salt water, Kool-Aid chocolate chip cookie
muddy water salad dressing air

6 Pure Substances... Pure substances are made up of only one type of particle and therefore look the same all throughout.

7 Examples of Pure Substances
sugar (C12H22O11) gold (Au), copper (Cu) distilled water (H2O) carbon dioxide (CO2) oxygen (O2)

8 Mixtures: Mixtures may be: Homogeneous (also called solutions) Or
Heterogeneous (also called mechanical mixtures)

9 Homogeneous Mixtures These mixtures appear to be the same throughout and often have the same properties: -only one part visible (appears to be one substance) -usually transparent -light passes through unaffected - particles do not settle, they dissolve

10 the particles are evenly mixed so that none of the original substances are visible (dissolved)

11 Homogeneous Mixture can be: solid liquid or gas Stainless steel
Salt water Clean air

12 More Examples of Homogeneous Mixtures
Apple juice Kool aid Salt water Stainless steel Brass Clean air

13 Heterogeneous Mixtures
Have different visible parts, each with their own properties - two or more parts visible to the eye - not transparent - particles settle and they do not evenly mix -Light will scatter

14 Heterogeneous Mixtures
can include: solids liquids or gases Granola bar Oil and vinegar Polluted air

15 Examples of Heterogeneous Mixtures
Sand and water Granola bar Tossed salad Pizza Cement Polluted air Oil and vinegar Salad dressing

16 Homogeneous or Heterogeneous
3 techniques can be used to distinguish between the two: Use a microscope. A solution contains only one type of particle Use a filter. If anything gets caught in the filter it is a mechanical mixture. Tyndall effect. Mixtures scatter the light (you can see it ) and solutions do not scatter light (you cannot see it).

17 Tyndall Effect The tyndall effect can be used to tell the difference between a solution and a mixture. cannot be used to distinguish between a solution and a pure liquid How? If you shine a beam of light directly through a mixture and you do not see the beam, it is probably a solution. The particles are evenly mixed at the molecular level so they will not block or scatter the light. Left: Silver colloid mixture Right: Tap water

18 In a Solution... Light passes unaffected (if a student looks at the beaker perpendicular to the direction of the beam they will NOT see it

19 In a Mechanical Mixture...
The light will scatter as it passes through the mixture because all particles are not dissolved (as shown on the left)

20 Mechanical Mixture or Solution?

21 Flow Chart Matter Pure Mixture Heterogeneous Homogeneous
Mechanical Solution mixture

22 Some mixtures may be both homogeneous and heterogeneous
Example: orange juice The large pulp particles make it a heterogeneous and the sugar molecules dissolved in it make it homogeneous.

23 Colloids A colloid is a type of mixture that appears to be a solution but it is actually a mechanical mixture

24 Solid Sol Examples: cranberry glass, ruby glass
Examples of colloids Dispersed medium Gas Liquid Solid Continuous Medium Gas NONE (All gases are mutually miscible) Liquid Aerosol Examples: fog, mist Solid aerosol Examples: smoke, air particulates Foam Examples: whipped cream Emulsion Examples: mayonnaise, hand cream Sol Examples: milk, paint, pigmented ink Solid Foam Examples: aerogel, styrofoam, pumice Gel Examples: butter, gelatin, jelly, cheese, opal Solid Sol Examples: cranberry glass, ruby glass

25 Suspensions Suspensions are a heterogenous fluid containing solid particles will settle over time if left undisturbed Examples: Mud or muddy water, is where soil, clay, or silt particles are suspended in water. Flour suspended in water Fog is water suspended in air. Paint Chalk powder suspended in water. Dust particles suspended in air.  

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