Teach your kids about density by making a homemade lava lamp. This project will show them how a liquid with a low density will float on water, while a highly dense material will sink. This is a great project to do on a rainy day or any day your kids need something to do. It only takes a few minutes to make the lava lamp, but it will keep them occupied for hours. Use items from around the house and the entire project will be free.
Things You'll Need
To make your own lava lamp, you'll need a clean plastic bottle or glass jar, vegetable oil, water, Alka-Seltzer or salt and food colouring. Cover your workspace with a large towel or tablecloth to protect it from oil and food colourant. Gather all of your supplies ahead of time, because you will need each of them in consecutive order.
Make a Lava Lamp With Alka-Seltzer
Pour vegetable oil into a clean, plastic bottle until it is about 3/4 full, and then fill the remainder of the space with water. Add 10 to 15 drops of food colouring or more until the mixture is a dark colour. Cut the Alka-Seltzer tablet into eighths, and then drop it into the mixture one piece at a time. Allow the piece to completely dissolve and stop bubbling before adding the next piece of Alka-Seltzer.
Use Table Salt to Make a Lava Lamp
Pour 3 to 4 inches of water into a glass jar and then add several drops of food colouring. Fill the remainder of the jar with vegetable oil. Remember that oil and water don't mix, and after sitting for a few seconds the oil with form a layer on top of the water. Add several teaspoons of table salt to the layer of oil. This should thicken the oil, causing it to drop to the bottom of the jar. The oil will float to the top of the water after the salt starts dissolving in the water. Shake additional salt onto the oil and the process will repeat.
Make Your Homemade Lava Lamp "Light Up"
Cover the bottle or jar with a lid, and shake gently to watch the lava move back and forth. Shine a flashlight under the bottle or jar to brighten the lava and bubbles, or place the lava lamp in front of a night light or small electric lamp after shaking it up to watch the bubbles move.