Why does double cream become stiff when it’s whipped? Try our kids’ quiz

Illustration: Hennie Haworth/The Guardian

1. Kathryn, 11, asks: why does double cream become stiff when it’s whipped?

   1. The cream gets annoyed with being whipped and grows big and angry

   2. It gets hotter when it is whipped and expands

   3. The cream reacts with the cold of the metal whisk

   4. The fat molecules break down and arrange themselves around air bubbles

2. Millie, 8, asks: how do we know how old the Earth is?

   1. By sampling rocks from meteorites and the moon

   2. By cutting it open and looking at its rings

   3. By studying fossils from the ocean floor

   4. By examining the writings of ancient civilisations

3. Lizzy, 8, asks: what is the official currency of China?

   1. Renminbi

   2. Yuan

   3. Chinese dollar

   4. Lao kip

4. Thali, 7, asks: what is the world’s oldest active volcano?

   1. Stromboli

   2. Ben Nevis

   3. Volcano Meji

   4. Mount Etna

5. Tovah, 3, asks: why do clouds move?

   1. The spinning of the Earth creates a centrifugal effect, making them move

   2. They don’t: the Earth moves so it looks as if clouds are moving

   3. The same gravitational forces from the moon that move waves, move them

   4. The wind carries them

Solutions

1:D - Cream is made of the fatty layer on the top of milk; it’s full of water, milk sugars, protein and lots of fat. When you whip it, little bubbles of air get trapped in the mixture. The fat droplets break up and the molecules arrange themselves around the air bubbles, so the air can’t escape and makes the cream grow bigger until it goes stiff., 2:A - The Earth is around 4.6bn years old. Scientists tell this from samples from the moon and other meteorites. They study radioactive materials in the rocks, whose atomic structures divide in a predictable and consistent manner over time., 3:A - The official name is renminbi, meaning “the people’s money”. But yuan is a unit of this currency, so that is often used instead., 4:D - Studies of Mount Etna in Sicily, Italy, suggest it has been going for about 2.6m years and is Europe’s most active volcano. It was already very old when its first recorded eruption took place in 1500BC; since then, it has erupted at least 200 times., 5:D - The wind carries clouds through the air. Even when it seems there is no wind on the ground, there may be higher in the atmosphere.

Scores

1. 5 and above.

2. 4 and above.

3. 3 and above.

4. 2 and above.

5. 0 and above.

6. 1 and above.

Molly Oldfield hosts Everything Under the Sun, a weekly podcast answering children’s questions, out now as a book.

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