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Mixtures

In many mixtures, like concrete or granola, you can clearly see the

separate pieces or components. Each spoonful of granola is different. If you pick up a spoonful of wet concrete, it may or may not contain a pebble. This type of mixture is called a heterogeneous mixture (heterogeneous means “different kinds”), because two or more substances can be seen and felt. You could easily separate the components (parts) of the mixture! If you take a small sample from such a mixture, it may have different properties from another sample. Another name for a heterogeneous mixture is a mechanical mixture.

You see and use mechanical mixtures almost every day. To find a

mechanical mixture, you could look inside your closet at home or inside your pencil case at school. Maybe you ate a mechanical mixture for breakfast, such as cereal and milk, or a banana chocolate chip muffin. Figure 1 below shows three more examples of mechanical mixtures.

Heterogeneous (Mechanical) Mixture: A mixture with different parts that you can see.

Figure 1 – How can you tell that each of these images represents a

mechanical mixture?

Some mixtures do not look like mechanical mixtures. They look like pure substances. Like the grape juice in Figure 2 below, shampoo looks like only one kind of matter. However, both grape juice and shampoo are mixtures. Grape juice contains water particles, sugar particles, and flavour particles. Shampoo contains water particles, detergent particles, colour particles, and scent particles.

Figure 2 – Shampoo and grape juice are both mixtures, even though they look like pure substances.

Mixtures that look as though they are pure substances are called solutions. A solution contains more than one kind of particle, but it looks like a pure substance. Solutions are sometimes called homogeneous mixtures. Both steel and seawater are solutions. Clear apple juice is a solution. The air you breathe is also a solution.

In a homogeneous mixture (homogeneous means “same kind”),

the particles of the pure substances mix together so completely that the mixture looks and feels as though it is made of only one substance. You cannot easily separate the components (parts) of the mixture! No matter what size of sample, the properties of this mixture are always the same. Homogeneous Mixture (Solution): A mixture that looks like a single pure substance; a uniform mixture of two or more pure substances.

Figure 3 – (a) The different particles of a solution (homogeneous mixture) are evenly mixed. (b) The different particles of a mechanical mixture (heterogeneous mixture) are unevenly mixed.

MATTER

PURE SUBSTANCES MIXTURES

HOMOGENEOUS MIXTURES

(SOLUTIONS)

HETEROGENEOUS MIXTURES

(MECHANICAL MIXTURES)

Can combine to form …

Check Your Understanding – Mixtures

1. List five homogeneous mixtures (solutions) and five heterogeneous (mechanical) mixtures found in your home.

2. Search your home for at least four different mixtures (you may use examples from the previous question). Try to find a variety of mixtures, including the following:

• a mixture of two or more solids • a mixture of two or more liquids • a mixture made by mixing a solid and a liquid • a mixture made by mixing a liquid and a gas

Fill out the following table for the above mixtures: Mixture 1 Mixture 2 Mixture 3 Mixture 4

Name of Mixture

Mechanical Mixture or Solution?

Components (Parts) of Mixture