Basic Concepts
In a nutshell: Physical changes affect appearance but not identity, while chemical changes create something new.
## How Matter Transforms
Matter can change in many ways. These changes are divided into two main types: **physical** and **chemical**.
### Physical Changes
A physical change alters how something looks or feels but doesn't change what it is. Examples include:
- Tearing paper
- Melting ice
- Dissolving sugar in water
After a physical change, the substance stays the same at the molecular level.
### Chemical Changes
A chemical change creates something new. The original substance becomes a different material with new properties. Signs of chemical change include:
- Color change
- Gas formation (bubbles)
- Temperature change
- Formation of a solid (precipitate)
Baking a cake, rusting iron, and burning wood are all chemical changes.
## Why Do These Changes Matter?
Understanding these changes helps us cook, clean, create new materials, and even understand how our bodies work!
Examples
- Melting butter is a physical change; frying an egg is a chemical change.
- Rust forming on a bike is a chemical change; cutting vegetables is a physical change.