Making a lava lamp!
Making a lava lamp is one of those easy to do activities that keeps the kids enthralled for ages. All you need is some oil, a clear jar, some food colouring and alka seltzer. Put a small amount of water at the bottom of the jar and then fill up the rest of the jar to the 3/4 mark with the oil. Pipette in about 10/15 drops of your chosen food colouring and then put the alka selzer in and watch it fizz. As you can see, my preschooler was fascinated watching this!
The science behind it…
Water and oil are immiscible i.e. they don’t mix, and water is denser than oil. This means that water sits below the oil. The food colouring droplets attach to the water molecules. When the alka selzer is added, it forms carbon dioxide gas. This gas bubbles up through the oil and the bubbles attach to the coloured water so that it rises up through the oil too. When the bubble pops at the top, the colour globules sink to the bottom again.