Show students you can't always see a physical change, such as when a liquid turns into a gas. Fill a plastic bottle halfway with water. Smash an antacid tablet into a few pieces. Place the tablets into the water carefully and quickly. You or another adult assistant places the mouth of a balloon over the mouth of the bottle as quickly as possible. The balloon expands with the gas coming from the reaction of the tablets with the water in the bottle. Remove the balloon after 60 seconds; it is still full of gas. Drain and throw out all materials after you record what you see. Wash your hands thoroughly.
Demonstrate to students how much of the air is made up of oxygen, and that the composition of the air itself can cause a physical change on metal called rust. To perform, wet a large piece of steel wool and push it to the bottom of a glass jar. The steel wool should be big enough so you can tip the jar upside down, and the wool doesn't move. Pour 4 cm of water into two clear plastic containers. Turn two jars -- the one with the steel wool and one without -- upside down inside the water in the containers. Put a rubber band around both jars where the water level in the container hits the jar. Leave undisturbed for two days. Note the change in water level in the jar with the steel wool, compared to the one without. As the steel wool rusts, it removes oxygen from the air and water is sucked up into the jar.
Make a type of polymers which are goopy and gooey to the touch. For ingredients, you need water liquid glue, powdered laundry detergent and liquid starch. Gather paper towels, measuring spoons, plastic cups, and spoons. For the first recipe, mix 1 tsp. glue with 1 tsp. water in a small cup. Place 1 tsp. detergent into a separate cup with 1 tbsp. water and mix. One student stirs the glue and water while her partner slowly mixes in the detergent and water. When the solution becomes globby, drop it between two paper towels to soak up excess moisture. Students can now experiment with and observe the properties of the glob. Record the physical changes observed at each step of the process.
Water is a unique liquid, and liquids that appear as clear, colorless and odorless as water act much differently than water does. To prepare, have three clear plastic cups, masking tape, a pen, water, isopropyl alcohol, mineral oil, straws, wax paper and a brown coffee filter. Students put on goggles before they begin. Put a piece of tape on each cup and label them water, oil and alcohol. Place 1/2 tsp. of each liquid into each cup. Drop a single drop of each liquid onto a piece of wax paper, using three different straws. Tear open the coffee filter and repeat the process by placing drops on the filter. Record how each liquid acts in the plastic cup, on the wax paper, and on the paper filter.