Lesson 15 of 19
Useful and harmful changes
Show on a big screenCurd is a useful change in milk. Rust is not a useful change.
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The idea
Decay means rotting. Compost is rotted waste that helps plants grow.
Step 1 of 3
- Food decays. Is that good or bad?
- In a cupboard, it spoils our food. This is undesirable.
- In a pit, it makes compost. This is desirable.
Idli batter rising and fallen leaves turning into soil are desirable. Rust, and the fuzzy mould on stored food, are undesirable.
A desirable change helps us. An undesirable change harms us. The same change can be both.
Try the lab to finish this lesson.