The k8 school logo

Online Homeschooling Website

“When the power of love overcomes the love of power, the world will know peace” – Jimi Hendrix

Reversible changes


What is a reversible change? A reversible change is a change that can be undone or reversed.

 

Give another name for reversible changes.

Physical changes

 

Why we call them physical changes?

 

  • A reversible change might change how a substance looks or feels (Changing the physical appearance), and it is easy to turn it back again.
  • But it doesn’t produce new substances.

E.g. – Water can change into ice. Ice can change into water. Here only the state of the substance (liquid water) changes, but not the substance (water).

 

Examples of reversible changes.

 

Melting

Example (1) – When chocolate is warmed until it melts, the melted chocolate can be changed back into solid chocolate by cooling.

Reversible Changes Examples Melting Chocolate
 

Example (2) -When candle wax is heated, the solid wax melts and becomes a liquid. If you cool the molten wax, it becomes a solid again.

Reversible Changes Examples Melting Wax

Freezing

Example – When orange juice is frozen to make ice lollies, the ice lollies can be changed back into orange juice by heating.

Reversible Changes Examples Freezing Ice lollies
 

Boiling, evaporating and condensing (changing a gas into a liquid)

Example (1) – If you could capture all the steam that is made when a kettle boils, you could turn it back to water by cooling it.

Reversible Changes Examples Evaporating

 

 

Example (2) – When we put some water in the freezer of a refrigerator it will turn into ice. If we then warm ice it melts and changes back into water.

Reversible Changes Examples Freezing Ice

 

Dissolving

Example (3) – When salt is mixed with water it disappears because it dissolves in the water to make salty water. But the salt can be recovered from the salty water by boiling off the water.

Reversible Changes Examples Dissolving

 

 

Changing the shape of a substance

Example (1) – When you cut a piece of wood in half, you change its shape. But you do not alter the way the wood is made.

Example (2) – When you stretch an elastic band, you alter its shape but it is still made of elastic.