Activity Name: Mixtures and Solutions

Target Subject: Physical Science

Purpose: To create heterogeneous and homogeneous mixtures and solutions, identify the differences, and to explore the concepts of concentration and dilution.

Background Information: Mixtures contain more than one kind of particle, (atoms, molecules, and or compounds). A heterogeneous mixture contains particles that are not the same, can be separated by physical means, and are not distributed the same throughout the mixture.Trail mix is a good example.

In homogeneous mixtures and solutions the particles are distributed evenly throughout the mixture and are not easily separated. A thoroughly mixed glass of lemonade is a good example. In science the lemonade powder, or whatever is being dissolved, is referred to as a solute. The substance doing the dissolving is called a solvent. In the lemonade solution, water is the solvent. The amounts of solvent and solute can be changed to create various concentrations of the solution from dilute to concentrated, or even oversaturated, where no more solvent will dissolve.

Preparation: Depending on the experience of the students and the time available, this activity can be presented as three different activities or done sequentially. Preparation involves obtaining the various supplies listed in the materials list.

Materials: Trays Bowls Cups Ingredients for trail mix such as small candies, raisins, pretzels, etc. Variety of small none edible objects such as buttons Powdered drink mix

Water Spoons or stirring rods Rubber gloves

Procedure: 1. If use of food is permitted in the setting, create trail mix by adding

a small amount of separate ingredients from individual containers into one large bowl. Following a recipe for trail mix gives practice in measuring skills.

2. Mix with gloved hands. Divide into small containers and eat noticing the variety and numbers of items in the mixture and how easily they are separated.

3. If food is not allowed or available, use a variety of small objects such as buttons, bells, and pompoms. The different sizes and textures will support the idea of heterogeneous mixtures.

4. Follow the same procedure as described above, except after the items have been combined in one large bowl they can be tactually re-separated back into the original containers.

5. Make a powdered drink mix with water to illustrate how a homogeneous mixture is not easily separated.

6. While stirring with a spoon or stirring rod, note the gritty feeling of the crystals before they dissolve. An effective stirring technique to facilitate dissolution is stirring in a circle a few times then stirring in a zigzag line back and forth across the container.

7. Alternate these methods until the crystal seem to disappear. They have not vanished; they are in solution, hanging out between the molecules of water.

8. If allowed, taste the water before the crystals are added, then after they have dissolved, and note the differences.

9. The concepts of diluted and concentrated solutions can be experienced by adding more or less of the solute (the powdered drink mix).

10. Salt and water provide an easy way to show that some solutions can be separated by evaporation. Tactually observe the crystals dissolving. After the salt solution is left to evaporate, feel the crystals that have reformed in the container and note that the water has evaporated.

Safety Note: Remember lab materials should never be tasted unless directed by instructor.