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Changes Around Us: Physical and Chemical

Useful and harmful changes

Curd 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.

Food decays. Is that good or bad?
Step 1 of 3
  1. Food decays. Is that good or bad?
  2. In a cupboard, it spoils our food. This is undesirable.
  3. 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.

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This track

  1. 0 Start here
  2. 1 Fold it, cut it, crumple it
  3. 2 Ice, water and steam are one substance
  4. 3 Dissolving is not disappearing
  5. 4 Some of these will not go back
  6. 5 Checkpoint: changes that make nothing new
  7. 6 A test for something new
  8. 7 Five signs, and what each one is worth
  9. 8 One candle, two changes at once
  10. 9 Two questions, not one
  11. 10 Slow changes in rocks
  12. 11 Checkpoint: new substances and the two questions
  13. 12 Burning needs air
  14. 13 The fire triangle
  15. 14 A change written in words
  16. 15 Useful and harmful changes
  17. 16 Checkpoint: burning, equations and useful changes
  18. 17 The big picture
  19. 18 Track quiz

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