Basic Science · Primary 4
At home: changes that cannot be undone
Prompt PPJ-SCI-02252
🦉 Learn it
Some changes can never be undone. We call them irreversible changes. A new material is made, and you cannot get back what you started with.
When Mama cooks rice, the hard grains become soft. You cannot make cooked rice hard and raw again. When firewood burns, it becomes ash and smoke. You cannot turn ash back into wood.
Signs of an irreversible change: a new smell, a new colour, smoke, or something that will not go back however much you warm or cool it.
Tunde's rusty nail
Tunde finds an old nail by the tap. It is covered in orange-brown rust. Rust is a new material made when iron meets water and air. Scrubbing hard cannot turn rust back into shiny iron.