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Changes Around Us: Physical and Chemical

Dissolving is not disappearing

Sugar is stirred into water. The glass looks clear. Is the sugar still there?

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The idea

Sugar sits at the bottom of the glass.
Step 1 of 4
  1. Sugar sits at the bottom of the glass.
  2. Stirred. The sugar spreads through the water.
  3. Left in the sun. The water dries off.
  4. The sugar is back. Same weight as before.

The rule

Yes, the sugar is still there. Dissolving means spreading through water in tiny pieces.

Sugar in water is spread too thin to see. Drying the water brings the sugar back. Only the water dries off, so the sugar is left behind.

Nothing new is made. Dissolving is a physical change. Sea water works the same way. In shallow pans, the water dries and the salt remains.

Jump to lesson

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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