This is a great experiment to help introduce seventh-graders to the idea of air pressure as it relates to both liquid water and water vapor. First, have your students clean out an empty can of their favorite soda. Next, have them put just enough water inside the can to cover just the bottom. With a standard heat-element burner, heat the can until the water inside starts to boil; the boiling indicates that the water inside the can has been turned into water vapor. Have your students carefully use a pair of metal tongs to lift the can and place it upside down into a bowl of ice water. The moment the can comes in contact with the cold water, the higher-pressure vapor inside the can will convert back into a few measly drops of liquid water. This will drastically lower the air pressure on the inside of the can, which will “magically” crush in on itself due to the greater external air pressure.
This is a fun, hands-on activity to demonstrate the principle of centripetal force that seventh graders are sure to enjoy. Have your students fill a plastic beach bucket halfway with water. Next, have them secure one end of a sturdy rope to the handle of the bucket. Finally, instruct your students to grip the other end of said rope securely in their dominant hand, and then spin the bucket in a vertical loop. Thanks to the power of centripetal force, the water will remain in the bucket even when the bucket in completely inverted, as long as the student continues to spin the bucket. Explain to your students that centripetal force – acting in tandem with centrifugal force -- is what keeps the moon in orbit of Earth.
Here’s a nice experiment to help your seventh-graders practice the scientific process of testing the simple hypothesis that a person’s dominant hand is more sensitive than their non-dominant hand. After recording whether each test subject is right-handed or left-handed, your students will have their subjects submerge both of their hands in a big bowl of ice water. Each test subject will be instructed to remove their hands only when that hand is too uncomfortable. Have your students record whether the first hand that each of their subjects removed from the ice water was that subject’s dominant hand. Later your students can compile their data into a chart to confirm or reject the hypothesis.
This is a great experiment that will help students observe the differences between solids and liquids, while at the same time getting a wake-up call regarding the sugar-content of generic soda. This experiment will have your students practicing the scientific process by discovering exactly how much sugar is in a regular can of soda. First, have your students pour a can of soda into a small pot. With a burner, bring the soda to a boil, and keep boiling until all of the water has evaporated and all that remains is the soupy remains of the sugar. Have the students weigh the entire pot, and then subtract the weight of the pot itself. This should give you a fairly accurate weight for the sugar that approximates the number stated on the label of the can. Finally, have your students measure out an equivalent weight of regular white sugar and have them pour that sugar into a drinking glass. Your students will be visually amazed out how much sugar they ingest with a single can of soda.