Changes we want, changes we do not

The idea

Some changes are desirable and some are undesirable, and a change that is undesirable in one situation may be desirable in another.

Wanted or not?

Changes happen all around us. Milk turns into curd. Iron rusts. Food decays.

Do we want every change to happen?

• Yes, we want every change
• No, we want some and not others
• We do not want any change

Sort the changes

Sort each change. A desirable change is one we want. An undesirable change is one we do not want. Watch the last card.

Desirable or undesirable

Decomposition of food can be very useful in converting food waste into compost.

Some changes are desirable and some are undesirable. A change that is undesirable in one situation may be desirable in another.

• Change | We call it
• Milk changes into curd | desirable
• Ripening of fruits | desirable
• Cutting of fruits | desirable
• Cooking of food | desirable
• Rusting of iron | undesirable
• Decay of food during storage | undesirable
• Decay of food waste in a compost pit | desirable

Notes

Some changes are desirable and some are undesirable. A change that is undesirable in one situation may be desirable in another: decay of food in storage is undesirable, but decomposition of food waste into compost is useful.

Check yourself

Which of these is an undesirable change?

Food decays in a kitchen cupboard. Food waste decays in a compost pit. Which one is desirable?

A change that is undesirable in one situation may be _ in another situation.

Milk into curd, rusting of iron, cooking of food, decay of food in storage and ripening of fruits. How many of these five are desirable changes?

Answer: 3

Three: milk into curd, cooking of food and ripening of fruits. Rusting and decay in storage are undesirable.

• Milk changing into curd. We want milk to change into curd. It is a desirable change.
• The rusting of iron — correct. Yes! We do not want iron things to rust.
• The ripening of a fruit. We want fruits to ripen. It is a desirable change.
• Only the decay in the cupboard. We do not want stored food to decay. It is undesirable there.
• Neither of them is desirable. In the compost pit the decay is useful: it turns food waste into compost.
• Only the compost pit one — correct. Yes! There, the decay turns food waste into compost.
• desirable — correct. Yes! Decay is undesirable in storage but desirable in a compost pit.
• impossible. The change can still happen. It may even be useful in another situation.
• reversible. That is a different idea. Here we ask if we want the change or not.