* Physical Change: Involves a change in the form or appearance of a substance, but not its chemical composition.

* Chemical Change: Involves the formation of new substances with different chemical properties.

Buoyancy Explained:

Buoyancy is the upward force exerted by a fluid (like water or air) that opposes the weight of an immersed object. It arises from the pressure difference between the top and bottom of the object, caused by the fluid's density.

* No New Substances Formed: The object doesn't change its chemical makeup when it's submerged. It simply experiences an upward force.

* Reversible: If you remove the object from the fluid, the buoyancy effect disappears, and the object returns to its original state.

Example:

A wooden block floating in water:

* The block's chemical composition remains the same (wood).

* The block simply experiences an upward force (buoyancy) that keeps it afloat.

Let me know if you have more questions!