The purpose of this activity is to determine which substances are soluble in water. This is a good opportunity to practice lab safety procedures and to teach the necessary vocabulary, such as soluble, solute and solvent. For this lab, begin with a variety of labeled substances. Include salt, sugar, baking soda, sand and any others of your choosing. Have students record in their lab notebooks which substances they found to be soluble.
This activity demonstrates the fact that more of a solid can be dissolved in a warm liquid than in a cold one. Begin with a discussion of real life experiences dissolving sugar in a cold or warm drink. Ask students for their prediction about the effect of water temperature on solubility. Then have students add sugar to water of different temperatures, a few grams at a time, until they have saturated the solution. This is a good activity for practicing temperature measurement, volume measurement and graphing.
In this activity, students will use what they know about the solubility of salt and sand to find a way to separate a mixture of the two substances. After leading them through a discussion of the solubility of both substances, challenge them to separate a mixture of the two using using water (heated if possible in your lab), glass jars or beakers, a funnel and a coffee filter. After dissolving the salt and straining the sand out, let the two components dry in shallow pans so that students can see the two substances separated.
Many harmful chemicals are water-soluble. Demonstrate for students the solubility of a household cleaner, calcium chloride ice melt, and plant fertilizer. Explain that many of these products can be carried by rainwater runoff into lakes, rivers and oceans. Have students use the Internet to research the impact of these products on bodies of water. Then have them create an informational brochure explaining how pollutants get into water and how the problem can be prevented.