• Quick retrieval from earlier learning (Heating and cooling: can the change be undone?). Students answer on mini whiteboards.
• Show answers together and note who needs support in the main task.

1. Can this change be undone: candle wax melting? (can change back / cannot change back) → can change backPrompt: Could you get the starting material back by warming it or cooling it?
2. Three of these changes CANNOT be undone. Which one is different? (butter softening in a warm kitchen / burning a log on a fire / popping popcorn / frying an egg) → butter softening in a warm kitchenPrompt: Think about melting and freezing versus cooking and burning.
3. Ice cream is left in the sun and melts. Then it is put back in the freezer. Is it the same as before? (It freezes solid again, though it may be icier and harder than before. / It stays a liquid in the freezer. / It turns into milk powder. / It burns.) → It freezes solid again, though it may be icier and harder than before.Prompt: Is melting a change that can be reversed?

• Show an ice cube melting and a kettle steaming and ask what is the same and what is different.
• Share the objective: What happens when we cool it?. Read the success criteria together.

• Work through the example out loud, saying why you do each step, not just what you do.
• Example: What happens when this cools down: hot candle wax left to cool?
• Step 1: So the answer is: turns back into solid wax
• Answer: turns back into solid wax
• Pause after each step and ask a student to say what comes next.

• Do these together. Students try each step on whiteboards before you reveal it.
• Use the hints as prompts rather than giving the answer.

1. What happens when this cools down: warm jelly mix in the fridge? (freezes into ice / turns into water droplets / becomes an ice lolly (popsicle) / sets into a wobbly solid) → sets into a wobbly solidPrompt: Cooling often turns liquids into solids, and gases into liquids.
2. Why do ponds freeze on cold winter nights? (The fish make ice. / The Moon cools the water. / The water cools below 0 °C and turns to ice. / Snow falls into the pond and makes it solid all the way down.) → The water cools below 0 °C and turns to ice.Prompt: At what temperature does water freeze?

• Students work on the student sheet. Circulate and check the first two answers of every student early.
• Students who finish: write a question of their own for a partner, with the answer.

The 8 questions are on the student sheet below, with answers in the key.

• Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.

1. True or false? Frozen juice can never melt back into juice. (True / False) → FalsePrompt: Cooling usually turns gases to liquids and liquids to solids.
2. A cold drink can has drops of water on the outside on a warm day. Where did they come from? (The can is sweating like a person. / The drink leaked through the metal. / It rained on the can indoors. / Water vapour in the air cooled on the can and turned into droplets.) → Water vapour in the air cooled on the can and turned into droplets.Prompt: Air has invisible water vapour in it.

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-2.