Today is rung 3 of 5 on this topic
Matter, mixtures and chemical change
Can do: Distinguishes physical from chemical change, and knows matter is conserved even when it looks like it's gone.
Why it matters
Conservation of matter is one of the most counter-intuitive ideas in science and one of the most testable at home.
What it looks like when it's wobbly
Thinks dissolved sugar has disappeared, and that gas has no mass at all.
⏱️ Two-minute check
"If you dissolve sugar in water, does the water get heavier? How do you know?"
Solid looks like: Yes, because the sugar is still there — and they can propose weighing it.
The full activity for this topic · 25 minutes
Weigh It Before and After
- 1Weigh a glass of water, weigh the sugar, dissolve, and weigh again. Predict first.
- 2Discuss why the total is unchanged even though the sugar is invisible.
- 3Put vinegar and baking soda in a sealed bag and weigh before and after. It stays the same.
- 4Open the bag and weigh again. Now it's lighter — because the gas left.
- 5Sort five changes into physical and chemical, with reasons.
If it's too hard
Just the dissolving experiment with a prediction.
If it's too easy
Explain why a burning candle appears to lose mass, and what would have to be measured to check.
Say this
"Where did it go? It can't just stop existing. What would we have to weigh to prove it?"