The physical properties of water change.
In Minecraft there is free flowing water, ice, and snow.
Students can explore the world to find these three forms of water and discuss their differences. For example, students can stand on snow and ice, but they will sink down in water. Also, ice is much harder than snow, but snow is much more supportive than water.
To extend the lesson, ice can be turned into water and by mixing water and snow, they can make ice.