Lesson Plan - Get It!
Describe how you make a fruit salad. Can chemistry be that tasty?
Fruit salads are made up of different fruits, like strawberries, bananas, blueberries, and grapes.
Each of these fruits can be cut into different size pieces, but they are easy to identify as part of the salad. Fruit salads are a good representation of a mixture. In chemistry, mixtures are substances that have been physically mixed. Generally, mixtures can be separated apart into the components that make them up. For example, I could separate out all the fruit in my salad by type.
There are two types of mixtures: heterogenous and homogenous.
- A heterogenous mixture is similar to the fruit salad example because it is easy to identify the materials in the mixture. A heterogenous mixture may include all three phases of matter: solids, liquids, and gases.
A smoothie has both solid and liquid materials, making it a heterogenous mixture. It is also an example of a suspension, because the substances will settle out over time. The heavier, larger particles will sink to the bottom, while the liquid concentrates at the top.
- In a homogenous mixture, the substances are uniformly mixed. That means it is very hard to tell individual components apart. Think about making Kool-Aid: once you have mixed the powder, water, and sugar together, you cannot identify individual substances.
Another name for homogenous mixtures is solutions. Solutions are made up of materials mixed together so that individual components are not visible. Solutions include soda, laundry detergent, and mouthwash. These examples are mixed so that you cannot identify individual parts!
Did you know that jello and milk are also solutions? They illustrate a special type of solution, called a "colloid." A colloid has larger particles than a liquid solution, but the materials are mixed in the same uniform way as a liquid solution.
Not every substance is found in a mixture; some are considered pure. Elements and compounds are examples of pure substances, because they cannot be isolated into components. Compounds exist in nature with set ratios between the elements. For example, sodium chloride will always have one sodium and one chlorine atom. It cannot exist with any other ratio.
Pure substances and mixtures make up many of the food items we consume, the products we use to get ready in the morning, and the chemicals that provide us resources.
- Pure substances are made up of all the elements located on the periodic table, as well as compounds that are chemically bonded together.
- Mixtures are physically combined, and can exist as heterogenous or homogenous, based on the composition.
- A heterogenous mixture has easily identifiable parts, while a homogenous mixture is made up of materials that are uniformly blended. Another name for a homogenous mixture is solution, which you will learn more about in future lessons.
Continue on to the Got It? section, where you will learn about separating the components in a mixture.