Watch water boil. With a grown-up at the stove, put a thermometer in a pan of water and heat it. Write down the temperature every minute. When it boils, keep watching. The number stops at about 100 °C, even though the heat is still on. The heat is going into making steam.

Before chapter 3. Beto wants to open the base to fix the switch. Is that where the fault is?

The answer. No. A kettle switches itself off when steam reaches a small metal disc and warms it until it snaps. The lid seal was cracked, so the steam escaped round the lid and never reached the disc. In the book a 3000-watt kettle heats 1.5 litres to boiling in about three minutes.

Safety. Anything that plugs into the wall is a grown-up's job. In the book, the children only ever touch the kettle cold and unplugged, and a grown-up does every test.

Pause to think. What did Beto keep in this book, apart from the kettle?

The grown-up layer. HeatForge has boiling, steam and conduction to explore safely on screen.

For the ride home. Ask: why does a pan lid make water boil faster?