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Pure Substances and Mixtures and Mechanical Solutions
Grade 7 Science - WillisPure Substances and Mixtures
Lesson 2
Learning Goals I can distinguish between pure substances
and mixtures.I can use the particle theory to describe the
difference between pure substances and mixtures.
I can distinguish between solutions and mechanical mixtures.
Pure Substances and Mixtures
Pure substances: matter that contains only one kind of particleE.g.: tin foil, table sugar, distilled water, salt
Mixture: matter than contains two or more pure substances mixed togetherE.g.: salt water, batteries, milk, air
Pure Substances and Mixtures
Is apple juice a pure substance or a mixture? Discuss
(Answer next page)
Pure Substances and Mixtures
Apple juice is a mixture of water particles, sugar particles, flavour particles and vitamin particles all mixed together.
Mechanical Mixtures and SolutionsScientists classify mixtures into two main
groups:
1. Mechanical Mixtures (also called heterogeneous mixture): a mixture with different parts that you can see. E.g.: cereal bars, omelettes, cookies
2. Solutions (also called homogeneous mixture): a mixture that looks like a single pure substance – uniform in appearance. E.g. tea, salt water, paint
Mechanical Mixtures and Solutions
Solutions can be in any three states: solid, liquid or gas, but only one state is visible at a time.
Mechanical mixtures can include different states in one mixture. (Think of breakfast cereal!)
Particles of MixturesIt may surprise you that clear apple juice, air
and steel are homogeneous mixtures, not pure substances!
Why?In a solution, the different kinds of particles
are mixed together evenly. In a mechanical mixture, the different kinds of
particles stay together in groups and are distributed unevenly. As a result, when you look at a mechanical mixture you can usually see the different kinds of matter.
Particles of Mixtures
Classifying MatterMATTER
Mixtures
Mechanical Mixtures
Solutions
Pure Substances
