* Physical changes alter the form or appearance of a substance but not its chemical composition.

* Chemical changes result in the formation of new substances with different chemical properties.

When you pour a liquid, you're simply changing its position and shape. The liquid itself remains the same chemically.

Here's an example:

* Physical Change: Pouring water from a pitcher into a glass. The water is still H₂O, it just has a different shape and location.

* Chemical Change: Burning wood. The wood reacts with oxygen to form ash, carbon dioxide, and other substances. This is a chemical change because the wood is no longer wood; it has transformed into something completely different.