The surface of a material controls lots of properties of a materials such as what it looks like, what it feels like and even how liquid behave on it.
In this activity collect some different materials and describe what each of them looks like and feels like and then use a magnifying glass (if you have one) to look at the surfaces and try to work our the differences between the surfaces and why this may give them different properties.
We have not yet made a specific video for this activity but this video is relevant: https://youtu.be/8Xog_UstOFY