* No new substances are formed: When you mix sand and water, you still have sand and water. The chemical composition of each substance remains the same.

* The change is reversible: You can easily separate the sand and water by letting the water evaporate or by using a filter.

* No chemical bonds are broken or formed: The process doesn't involve any chemical reactions that would create new compounds.

Key takeaway: Physical changes involve changes in the form or appearance of a substance, but not its chemical composition.