The big blue ocean
Most of our planet is covered by salty sea water. Find out where the salt comes from, what lives in the dark deep, and make an egg float!
Read
Look at a globe: most of our planet is blue. The ocean covers more of the Earth than all the land together.[1]
Almost all the water on Earth is in the ocean.[1]
All the oceans are joined into one big ocean. We give its parts names: the Pacific, the Atlantic, the Indian, the Arctic and the Southern Ocean.[2]
Sea water is salty. The salt comes from rocks on land. Rain and rivers carry tiny bits of it to the sea.[3]
At the top of the ocean the sun shines. Deep down it is always dark and very cold, and some animals make their own light.[8]
Tiny living things in the sea, too small to see, make a lot of the oxygen that we breathe.[7]
Try it: Can an egg float?
You need
- Two clear cups or jars
- Water
- Salt (about 6 big spoonfuls)
- A spoon
- A raw egg (or a small potato piece)
- Paper towels
Safety
Do not drink the salty water. Raw egg can carry germs: an adult handles the egg and everyone washes their hands afterwards. Wipe up spills so no one slips.
What to do
- Fill both cups with the same amount of water.
- Stir lots of salt into one cup until most of it is gone. Now it is salty, like the sea.
- Guess: will the egg sink or float in the plain water? And in the salty water?
- Gently put the egg into the plain water with the spoon. What happens?
- Lift it out and put it into the salty water. What happens now?
What happens, and why?
Salt water is heavier than the same amount of plain water. Things float more easily in salt water, so the egg sinks in plain water but can float in very salty water.[4]
Play: Sunny top or dark deep?
Does this belong in the sunny top of the ocean or in the dark deep? Tap the right place.
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Quiz
Other ages: Ages 10–11 · Ages 15–16