Science Class 7
Changes Around Us: Physical and Chemical
Two questions for any change: is it new, and can we undo it?
19 lessons · ~82 min total
Track progress — 0 of 19 lessons read 0%
Lessons in this topic
- 0 Start here Ice melts. An apple browns. Are they the same kind of change? · 3 min You are here
- 1 Fold it, cut it, crumple it Folding and cutting change the shape of paper. The paper stays paper. · 4 min
- 2 Ice, water and steam are one substance Ice, water and steam are one substance in three forms. The weight stays the same. · 4 min
- 3 Dissolving is not disappearing Sugar in water spreads too thin to see. Dry the water and the sugar is back. · 4 min
- 4 Some of these will not go back None of these make a new substance. Some still cannot be undone. · 5 min
- 5 Checkpoint: changes that make nothing new A quick check on shape, form, dissolving and changes that cannot be undone. · 4 min
- 6 A test for something new A chemical change makes a new substance. Lime water turning milky shows carbon dioxide. · 4 min
- 7 Five signs, and what each one is worth A colour, a gas, heat, a smell, a solid. Each is a clue, not an answer. · 4 min
- 8 One candle, two changes at once Wax melting is physical. Wax vapour burning is chemical. A candle has both. · 4 min
- 9 Two questions, not one Is something new made? Can we undo it? Two separate questions, four boxes. · 5 min
- 10 Slow changes in rocks Rocks change slowly. Some changes are physical. Some make new substances. · 4 min
- 11 Checkpoint: new substances and the two questions A check on lime water, signs, the candle, the two questions and slow changes. · 4 min
- 12 Burning needs air Combustion needs a fuel and oxygen. It gives out heat or light. · 5 min
- 13 The fire triangle A fire needs fuel, oxygen and heat. Take one away. · 5 min
- 14 A change written in words A word equation puts the starting substances on the left. · 5 min
- 15 Useful and harmful changes Some changes help us. Some harm us. A change can be both. · 5 min
- 16 Checkpoint: burning, equations and useful changes A quick graded check on burning, word equations and useful changes. · 4 min
- 17 The big picture The whole chapter on one screen. Two questions sort most changes. · 3 min
- 18 Track quiz A cheat-sheet of the rules, then one question per idea. · 6 min
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