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Science project idea

Three states of water in a bag taped to a sunny window

A zip bag with a little water and an ice cube, taped to a sunny window, shows all three states of water: the ice melts, the water evaporates, and the vapour condenses into drops on the cool upper part of the bag that run back down like rain.

Make it yourself7 numbered steps, the materials and the science, all free.Go to the stepsGet a ready-made kitReady-made models, kits and spare parts in the store under Chemistry.Browse ChemistryAsk on WhatsAppAsk the head office whether a model or kit for this idea is available.Send a message

What it shows

A zip bag with a little water and an ice cube, taped to a sunny window, shows all three states of water: the ice melts, the water evaporates, and the vapour condenses into drops on the cool upper part of the bag that run back down like rain.

The science

Water can be solid, liquid or gas depending on how much energy its particles have. Sunlight warms the bag, so the ice gains energy and melts, then surface water gains enough to escape as vapour. Vapour that touches the cooler top of the bag loses energy and turns back to liquid drops, which join and run down. The same three changes drive the water cycle outside.

Materials

Cost: free. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.

  • A clear zip-lock bag
  • A quarter cup of water
  • One ice cube
  • A drop of blue food colour, optional
  • Tape
  • A marker to draw a sun, cloud and sea on the bag

Safety

For this project: Close the bag fully so it does not leak; keep food colour away from clothes.

Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.

All the safety rules

Step by step

7 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.

  1. Draw a sun in one top corner of the bag, a cloud in the other, and wavy sea lines near the bottom.

  2. Pour the water in, add the food colour and the ice cube, and seal the bag tightly.

  3. Tape the bag flat on the inside of a window that gets morning sun.

  4. Check after thirty minutes and note whether the ice has melted.

  5. Look again after two hours for tiny drops forming near the cloud drawing.

  6. By evening, tilt your head to see drops running down the bag back into the water.

  7. Draw the bag at three times of day, labelling solid, liquid and gas where you saw each.

What you should see

Within a day the ice is gone, the upper bag is misted with drops and streaks show where drops have run down, giving a working picture of melting, evaporation and condensation in one bag.

Viva questions

A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.

1Where is the gas state in your bag?

The invisible water vapour in the air inside the bag above the water.

2Why do drops form at the top?

The top is cooler, so vapour there loses energy and condenses back into liquid.

3Did the food colour go into the drops?

No, the drops are clear because only water evaporates and the colour stays behind.

4What is this process called outside?

The water cycle: evaporation, condensation and rain.

Free ebook: Viva Questions for Science Projects

Take it further

Tape a second bag to a shaded window and compare how long the ice takes to melt and how many drops form.

Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.

Free ebooks for this project

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