Grade 7 Science Unit 3: Mixtures & Solutions: The Particle Theory

Particle Theory of Matter n All matter is made up of tiny particles. n These particles are always moving… they have energy.

n There are spaces among particles. n There are attractive forces between the particles. n The particles of one substance differ from the particles of other substances.

Matter can be either: n Pure substance n Mixture

Pure Substances... n ALWAYS appear as uniform throughout n A material that is only composed of one type of particle.

Sea shell- calcium carbonate

Examples of Pure Substances sugar gold, copper distilled water (H 2 O) carbon dioxide (CO 2 ) Table salt

Mixtures... n Composed of two or more types of particles. n MAY have distinct visible components.(heterogenous) n MAY appear uniform throughout. (homogeneous)

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

Examples of Mixtures… salt water, kool-aid chocolate chip cookie muddy water salad dressing air

Heterogeneous Mixtures pg 234 Also known as mechanical mixtures. n Contains 2 or more different particles and it is very easy to see the different parts. n It is easy to separate by hand or mechanical means such as filtration.

Examples n Chocolate chip cookie n Pizza n Cement n Salad dressing

Homogeneous Mixtures pg 234 n Also known as a ‘solution’ n Contains 2 or more different particles but the parts seem to be the same throughout. You cannot see the different parts.

Examples: n 14 Karat gold(58% gold & 42% other metals) n Stainless steel pan (iron and chromium) n Sugar and water n Salt water n Vegetable oil.

Heterogeneous, Homogeneous or Pure Substance: Cooking oil

Heterogeneous, Homogeneous or Pure Substance: n Beach Sand

Heterogeneous, Homogeneous or Pure Substance: n Oxygen

Heterogeneous, Homogeneous or Pure Substance: Fountain drink

Heterogeneous, Homogeneous or Pure Substance: n Salad

n Copper Heterogeneous, Homogeneous or Pure Substance:

Student Activity n Complete a three tab foldable which includes pure substances, heterogeneous mixture and homogeneous mixture. n Complete the worksheet

Is it a solution, mechanical mixture or pure substance? 1) You can use a microscope

Is it a solution, mechanical mixture or pure substance 2. If a liquid is a mixture, pour it through filter paper. See what happens…

Is it a solution, mechanical mixture or pure substance 3. The Tyndall Effect

If it is a solution (Homogeneous mixture) you will not see a beam of light. Heterogeneous you will…