Look at images and text through sandwich bags to learn about opacity and transparency, properties that are determined by light.
Start by holding one transparent polyethylene sandwich bag in the air. Can you recognise that light travels through the material, which allows them to see through the bag? Now, place the sandwich bag over a colour picture, a black and white picture then text, one at a time, rating how well you can see them through the bag. Then add a second sandwich bag, observing what effect the extra bag has and rating what they can see before adding more bags, one at a time and testing again as before. When the sandwich bags become opaque and you can no longer see through them, stop and record how many bags you have used.
Using water as a solvent, separate coloured ink from a range of pens through the process of chromatography.
Draw a series of dots, one for each coloured pen, near the bottom of a piece of blotting paper. Then stand the paper in a shallow pot of water. As the water is absorbed, it moves up the paper and carries the coloured inks with it. Because the inks have different properties, the colours get carried different distances. Examine the inks’ colour components when the paper has dried.