Physical changes and chemical changes are two important processes that change how materials work. Knowing the differences between them is important when learning about chemistry.

Physical Changes

• What It Is: A physical change changes the way something looks or feels, but it doesn’t change what it is made of.

• Examples:

  • When ice melts into water.
  • When you mix sugar into water.
  • When you break a glass.

• Things That Change:

  • State of Matter: Things can change from solid to liquid to gas (like ice melting).
  • Appearance: Size, shape, and color may change, but it’s still the same material.

• Can It Be Changed Back?: Most physical changes can be reversed. For example, you can freeze water back into ice.

Chemical Changes

• What It Is: A chemical change turns one substance into another by changing its makeup.

• Examples:

  • Iron rusting.
  • Burning wood.
  • Baking a cake.

• Things That Change:

  • Chemical Bonds: The connections between atoms break apart and new ones form, creating new substances.
  • Energy Changes: Chemical changes can release energy (like heat) or absorb energy.

• Can It Be Changed Back?: Chemical changes usually cannot be reversed easily. For example, you can’t un-bake a cake.

Important Points

• Measuring Changes: During a physical change, the weight usually stays the same. But in a chemical change, the total weight stays the same because of the law of conservation of mass.

• Statistics: In living things, over 95% of processes involve chemical changes. On the other hand, most everyday actions involve physical changes.

By understanding these differences, scientists can predict how materials will act in different situations.