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A Texas stock tank at midmorning with mist lifting, the Gulf of Mexico in the distance and clouds forming above.

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Sun, Ocean and the Water Cycle

Where most of the water is.

Lesson 26 of 41

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Before we start

Today’s story

Sun, Ocean and the Water Cycle

Look at a map of Earth. Most of it is blue. The ocean covers about three quarters of the planet. Almost all of Earth's water, about 97 percent, is in the ocean, and it is salty.

The Sun powers the water cycle. Its heat turns some water into water vapor, and this is evaporation. The vapor rises, cools and turns back into tiny drops, and that is condensation. Drops gather into clouds.

When the drops grow heavy, they fall as rain, snow or hail. That is precipitation. The water runs back to rivers and the sea, and the cycle starts again. Here are the steps.

See it

Five steps. Every time.

    Hands on

    Water Cycle in a Bag

    20 minutes plus one day · Do this with a grown-up nearby

    You need

    • a clear zip bag
    • water
    • blue food coloring
    • a marker
    • tape
    • a sunny window

    Do this

    1. Pour a little water in the bag and add a drop of coloring.
    2. Seal the bag tightly.
    3. Draw a sun and a cloud on the outside with the marker.
    4. Tape the bag to a sunny window.
    5. Check it every hour and the next morning.
    6. Notice where the drops form.
    Write or draw: Draw the bag at the start and at the end. Label evaporation, condensation and precipitation.

    Watch for: Water collects as drops high on the bag, then runs down. The color stays in the bottom because only water evaporates.

    Safety: Do not open the bag after it has been warm. Wash hands afterward.

    Same every time

    Three rules

    Rule 1The Sun is the engine.

    Without its heat the water would not move.

    Rule 2Water never disappears.

    It only changes place and form.

    Rule 3Most water is salty.

    Drinkable fresh water is a small share of the total.

    Grandpa Fenn’s notebook

    Say it like a scientist

    evaporation
    Liquid water turning into water vapor.
    condensation
    Water vapor cooling into tiny drops of liquid.
    precipitation
    Water falling from clouds as rain, snow, sleet or hail.
    water vapor
    Water as an invisible gas in the air.

    Poppy’s quiz

    Six questions

    Tap an answer. Green means right. You will see why.

    Talk about it

    Say it out loud

    • How do you know water in a puddle is going into the air? What evidence could you collect?
    • Where does the water in your tap or stock tank come from? Trace its path.
    Did you know

    The water you drink today is very old. It has been cycling between ocean, sky and land for billions of years.

    Someone who does this

    A hydrologist studies where water is and how it moves, in rivers, soil and sky.

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