Lava lamp experiment
Ingredients
*1 transparent glass or jar
*Water
*Cooking oil
*Food colouring
*1 antacid tablet
Method
*Fill the glass about one-quarter with water. Slowly pour cooking oil into the glass until it is almost full. Let the oil and water settle into separate layers.
*Add a few drops of food colouring. The colour will pass through the oil and mix with the water.
*Break the effervescent tablet into small pieces.
*Drop one piece into the glass and watch the colour rise and fall and move around like in a lava lamp.
What happened?
The tablet released gas that lifted the coloured water through the oil, and when the gas escaped, the colour blobs sank back down.
Raisins afloat
Ingredients
*2 transparent glasses/jars
*Water
*Cooking oil
*A handful of raisins
Method
*Fill one glass with water.
*Fill the second glass with cooking oil.
*Drop a few raisins into each glass.
*Observe the two glasses for the next few minutes. You will notice that the raisins will sink in water but float or move slowly in oil.
What happened?
Oil and water have different densities. Oil is thicker and lighter than water, which allows the raisins to float more easily.