One basic yet fun chemistry experiment gets your middle school students to investigate the relationship between salt and ice. Provide your students with four same-sized ice cubes and instruct them to place four glass beakers next to one another. Have students label each beaker with the following: "control," "half," "one," " and "two." Students should place one ice cube in each beaker beaker before adding half a teaspoon of salt to the "half" beaker, a whole teaspoon to the "one" beaker and two teaspoons into the "two" beaker. Students should start a timer the second they add the salt to the four beakers and, once each cube has melted, note down the time. Get students to think about the effect of salt on ice once each cube has melted.
This experiment with immiscible liquids gets middle school students to make something akin to a homemade lava lamp. First, students should 2/3 fill the glass beaker with tap water. Instruct students to add 1/2 a medicine dropper of food coloring. Inform students they will next add two tablespoons of oil to the beaker and get them to write down their prediction of what will happen. Have students add the oil and observe the results. Get students to then make their second hypothesis, which asks them to predict what will happen when they stir the contents of the glass. Have students stir the oil and water vigorously with a metal spoon and watch the results. Finally, get students to hypothesize about what will happen when they add a tablespoon of salt to the beaker. Have students add a tablespoon of salt and compare their findings to their hypothesis.
Middle school students will love this project, as they mix together different substances to produce their own fun polymer. Instruct students that they must wear rubber gloves throughout the experiment and that they must not ingest any of the substances. Get students to fill a one-cup measuring cup half way with hot tap water, add 1/2 teaspoon of borax powder and stir until dissolved. In a separate measuring cup, have students mix 1/2 cup of PVA glue and 1/2 cup of hot tap water thoroughly. Instruct students to mix the contents of each measuring cup together in a mixing bowl and knead the substance into a flexible solid using their gloved hands. Students should continue to knead for at least two minutes before pouring away any excess liquid and playing with their homemade polymer.
Middle school students can learn the chemical trick behind basic invisible ink during this fun project. Instruct students to pour 1/2 cup of concentrated lemon juice into a small bowl and, using a paintbrush and a plain piece of paper, write out a message by dipping the brush into the lemon juice and writing on the paper. Inform students that one coating of lemon juice might not be sufficient and so they may have to re-dip their brush into the lemon juice in order to fully write their message. Students should leave their paper to dry for at least 20 minutes, after which time they will see their message has disappeared. Get students to switch on a hot desk lamp and carefully hold their sheet of paper near --- but not touching --- the bulb for several minutes until their message starts to show up as a pale brown color.