Mixing, markets and new substances
Answers are for parents and teachers.
1
A cook mixes 150 g of rice with 60 g of lentils in a closed bowl. What is the mass of the mixture?
150 + 60 = 210 g.
2
In your kitchen, find three physical changes and three chemical changes. Write what makes each one that type.
Answers differ. Physical: melting butter, cutting bread, stirring sugar into tea. Chemical: cooking an egg, a banana going brown, baking a cake.
3
Explain why the damp iron nail rusted but the dry nail stayed shiny.
Iron needs water and oxygen from the air to make rust. The damp nail had water, the dry one did not.
4
Write a claim, evidence and reasoning to answer: does mixing change the total mass?
Claim: mixing in a closed container does not change the total mass. Evidence: 30 g + 20 g gave 50 g. Reasoning: all the particles are still there, and none escaped.
5
A glass of water has a mass of 250 g. A teaspoon of sugar of mass 5 g is dissolved in it. What is the mass now?
250 + 5 = 255 g.