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Science project idea

Stirring or warm water: which dissolves sugar faster?

Dissolving gets faster when the water is warmer, when the liquid is stirred, and when the sugar is in smaller pieces. A fair test with a stopwatch shows which of these three has the biggest effect.

Make it yourself8 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

Dissolving gets faster when the water is warmer, when the liquid is stirred, and when the sugar is in smaller pieces. A fair test with a stopwatch shows which of these three has the biggest effect.

The science

For sugar to dissolve, water molecules must bump into the sugar and carry particles away from its surface. Warm water molecules move faster, so they hit the sugar more often and harder. Stirring sweeps away the sugary water around the cube and brings fresh water to it. Crushing the sugar gives more surface for the water to attack. Each change speeds up the same process.

Materials

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

  • Sugar cubes or equal spoons of sugar, 6 portions
  • Six identical glasses
  • Cold water, room-temperature water and warm water (adult pours warm)
  • A spoon
  • A stopwatch or a phone timer
  • A notebook for the table

Safety

For this project: An adult must pour the warm water; it should be warm to touch, not boiling.

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

8 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. Fill three glasses with the same amount of cold, room-temperature and warm water.

  2. Drop one sugar cube into each at the same moment and start the timer without stirring.

  3. Note the time when each cube has completely disappeared; the warm glass should finish first.

  4. Refill two glasses with room-temperature water and drop a cube in each; stir one steadily and leave the other alone.

  5. Record the time for both; stirring should roughly halve the time.

  6. In a final glass of room-temperature water, drop a cube crushed to powder and time it.

  7. Make a bar chart of all the times with the glasses along the bottom.

  8. Write which single change made the biggest difference in your test and give a reason.

What you should see

A bar chart showing dissolving times, usually warm water fastest, then crushed sugar, then stirring, with the undisturbed cold cube taking several minutes.

Viva questions

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

1Why does warm water dissolve sugar faster?

Its molecules move faster and knock sugar particles off the cube more often.

2Why does stirring help?

It carries away the sweet water near the cube and brings fresh water to it.

3What made your test fair?

Same amount of water and sugar in every glass, changing only one thing at a time.

4Does sugar disappear when it dissolves?

No, it is still there, spread out as tiny particles; the water tastes sweet.

Free ebook: Viva Questions for Science Projects

Take it further

Repeat the whole test with salt and see whether the order of fastest to slowest stays the same.

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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