Wash out a small, plastic soda bottle. Fill it about one-third full of water. Drop in a few drops of food coloring for easier illustration. Pour vegetable oil into the bottle until it is about two-thirds full. Screw the lid back onto the bottle. Have your child shake the bottle as vigorously as possible. Watch as the water settles down to the bottom and the oil floats to the top every time. Drop in a few drops of liquid dish detergent. The detergent is attracted to both the water and the oil molecules and will cause them to emulsify. Discuss how this is helpful when washing greasy pots and pans.
Wash out a small, plastic soda bottle. Fill it two-thirds full of cooking oil. Add enough water to fill the bottle close to the top. Add about 10 drops of a dark food coloring to help track the water's movement. Cut an Alka-Seltzer tablet into eight pieces. Drop one little chunk into the bottle and watch as the colored water bubbles move throughout the liquid. When the bubbles die down, add another chunk. After you have used up all the Alka-Seltzer chunks and the bubbling has slowed, tip the bottle carefully on its side to watch a slow wave-like action of the colored blob, just like a lava lamp.
Wash out a small, plastic soda bottle. Fill it one-third of the way with water. Add a few drops of food coloring to illustrate the change to come. Add vegetable oil to the bottle until it is two-thirds full. Allow the oil to float to the top and the water to settle to the bottom of the bottle. Place the bottle in a freezer. After several hours, take out the bottle to examine it. Your child will see that the oil and water have switched places. The oil will be on the bottom and the water will be on top. Water expands when it freezes and therefore becomes less dense than the oil. This causes it to float over the oil when frozen. Thaw it out again and the water will settle below the oil.
Unfortunately, it seems every few years there is an oil spill that is large enough to make national news. When this happens, environmentalists scramble to clean the oil before it reaches the shoreline. Illustrate for your class how this is done. Fill a casserole dish with water. Shape a piece of aluminum foil like a boat. Pour in a good amount of oil into the boat. Tip the boat so that the oil spills across the surface of the water. Discuss how oil and water do not mix, making the cleanup possible. Give your students cotton balls to soak up the oil, which is the same principle environmentalists use. Talk about how environmentalists might carry away the oil-saturated material and how to best dispose of it.