6th Grade Science / Lesson 7 - Substances Mixes
What will we be learning today?
How Can Substances Be Mixed Together?
Can you think of examples of combining different substances together without changing the substances? Any combination of two or more substances in which the substances keep their own properties is a mixture. For example, a tossed salad is a mixture. You also make a mixture if you add sulfur and iron particles together. With a magnet you can easily separate the parts of this mixture, since a magnet attracts iron but not sulfur.
A magnet attracts iron but not sulfur. A magnet can be used to separate an iron-and-sulfur mixture Even though the substances in a mixture keep their own properties, you may not always recognize these properties. For example, perfumes are mixtures. If you separated the substances making up perfumes, you might find some of them have foul odors. However, when these substances are mixed together in perfumes, their odors blend to make a pleasing fragrance. If you were familiar with the odor of each substance, you could recognize it in the mixture. Perfume chemists can recognize odors of the individual substances in a mixture. Suspensions
One type of mixture is called a suspension. A suspension is a mixture made of parts that separate upon standing. An example is a mixture of soil and water. Products marked "Shake well before using" are often suspensions. Solid particles separate from a suspension by settling to the bottom. Fine particles, however, often remain suspended a long time. You can separate them by using a strainer or filter. Emulsions
Oil and water stay mixed only moments after shaking. For the short time that they are mixed together, however, they make up a kind of suspension called an emulsion. An emulsion is a suspension of two liquids that usually do not mix together Colloids
Fog is a mixture of fine water droplets in air. The droplets do not settle out. Fog is not a suspension. Rather it is an example of a mixture called a colloid . A colloid contains undissolved particles or droplets that stay mixed in another substance. Fog is a liquid-in-gas colloid. Smoke is a solid-in-gas colloid. Let's Review What We Learned Today!