Fact 1: Freezing causes a solid to form.

Fact 2: Freezing is a physical change.

Given the two facts above, answer the question "What causes solids to form?" with the following options: 
- Physical weathering
 - an external framework
 - Physical changes
 - adding sand
 - adding mud
 - heating liquids
 - adding water
 - A solid geometric shape


 

   Physical changes      