Gather samples of materials that are either good reflectors or poor reflectors (I had 10 different materials) and place them in a colour-coded envelop (folded coloured paper). I hid all envelopes around the room and told students they needed to find 4 DIFFERENT materials. They then glue the material into the correct box, and then proceed to analyze their findings in order to answer the next questions. I also mention to the kids that they should not have 4 good or poor reflectors (at least 1 of the other type), so that is why there are only 3 boxes for each.