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Class 5 · Science and environment

Sun or shade: which dries faster?

Two wet cloths: one in the sun, one in the shade. Which dries first, and how much faster?

What you will learn: Run a simple comparison and show results on a bar graph.

Small test at the end: scroll down to the end of this page for five short questions that check what you have learnt. Tap an answer, then press Check answer. Go to the questions ↓

Jump to: Check yourself · For grown-ups · For teachers

Safety first

Cap on, water to drink, and wait in the shade between checks.

Keep it safe:

  • Do not stand in strong sun for long. Wear a cap, stay in the shade between checks and drink water.
  • Hang the cloths at a height you can reach without climbing.

You will need

  • Two same-size clothsOld handkerchiefs or napkins.
  • A bowl of water
  • Clothes pegs and a line
  • A clock
  • Squared paperFor the graph.

Time: Set up in a few minutes. Check every 15 minutes until both cloths are dry; the example took 90 minutes.

The story

On washing day, Dadi hangs one dupatta in the sunny yard and another on the shady veranda. "The sunny one will dry first," says Tanmay. "Prove it," says Dhruv. "And how much faster?" A guess is a good start. How could they test it fairly, and show the answer on a graph?

The idea

To compare fairly, change only one thing. Here it is where the cloth hangs: sun or shade.

Keep everything else the same: the same kind and size of cloth, the same amount of water, wrung out the same way, hung at the same time.

Check every 15 minutes. A cloth is dry when it no longer feels damp or cool anywhere.

Show the results on a bar graph: a title, labels on both axes and an even scale. Results are for your test; repeat it to see if they hold.

A bar graph titled "Time for a cloth to dry". The bar for Sun reaches 45 minutes and the bar for Shade reaches 90 minutes. The vertical axis is minutes to dry, from 0 to 100.Time for a cloth to dry (one test)02040608010045Sun90ShadeMinutes to dryWhere it was hung
A bar graph titled "Time for a cloth to dry". The bar for Sun reaches 45 minutes and the bar for Shade reaches 90 minutes. The vertical axis is minutes to dry, from 0 to 100.

Worked example

Rahul's drying test

  1. Two same-size cotton cloths, each soaked and wrung out the same way.
  2. One hung in the sun, one in the shade, at 10 am.
  3. Checked every 15 minutes: the sun cloth was dry at 45 minutes, the shade cloth at 90 minutes.
  4. The shade cloth took 90 − 45 = 45 minutes longer: twice as long.

In this test, the cloth in the sun dried in half the time. Testing again on another day would show if this happens again.

Try it

  1. Make the cloths the same.

    Soak both cloths. Wring each out the same way, twice.

  2. Hang them.

    One in the sun, one in the shade, at the same time. Write the time.

  3. Check every 15 minutes.

    Touch each cloth. Damp or cool anywhere means not yet dry.

    Write the time each one is dry.

  4. Draw a bar graph.

    One bar for each place. Up the side: minutes to dry, in even steps.

    Add a title and labels.

  5. Write a conclusion.

    "In my test, the cloth in the ___ dried ___ minutes faster."

What you make (paper or offline)

Your drying graph

A bar graph of drying time: Sun 45 minutes, Shade 90 minutes.Time for a cloth to dry (one test)02040608010045Sun90ShadeMinutes to dryWhere it was hung
A bar graph of drying time: Sun 45 minutes, Shade 90 minutes.

A bar graph with a title, axis labels and an even scale.

A conclusion sentence using your numbers.

One thing you kept the same, and why.

Make it on paper. Keep it with you. Nothing to upload.

Check yourself

Five questions about what this page teaches. Choose an answer and press Check answer, or open "See the answer and why". Nothing is saved or sent: your choices stay on this screen and disappear when you leave or reload the page.

  1. Question 1 of 5In this test, what was changed on purpose?

    See the answer and why
    • A. The time they were hung Not this one. Both were hung at the same time.
    • B. The size of the cloths Not this one. Both cloths were the same size, so the test is fair.
    • C. The amount of water Not this one. Both were soaked and wrung out the same way.
    • D. Where it was hung Correct. Sun or shade: that is the one thing we changed. Everything else stayed the same.
  2. Question 2 of 5The sun cloth dried in 45 minutes and the shade cloth in 90 minutes. How many minutes longer did the shade cloth take?

    See the answer and why
    • A. 135 minutes Not this one. That adds the times. "How much longer" means take away.
    • B. 90 minutes Not this one. 90 minutes is how long the shade cloth took in all.
    • C. 2 minutes Not this one. It took 2 times as long, but 45 more minutes.
    • D. 45 minutes Correct. 90 − 45 = 45 minutes longer.
  3. Question 3 of 5Why must both cloths be the same size?

    See the answer and why
    • A. So only the place could matter Correct. If sizes differed, you would not know whether size or place made the difference.
    • B. So the graph looks neat Not this one. The graph is not the reason. A fair comparison is.
    • C. So they fit on the same peg Not this one. Pegs are not the reason. A fair test is.
    • D. Because a big cloth never dries Not this one. Big cloths do dry. They may just take longer.
  4. Question 4 of 5On the bar graph, what does the side axis show?

    See the answer and why
    • A. Minutes to dry Correct. The height of each bar shows how many minutes that cloth took.
    • B. The size of each cloth Not this one. Size was kept the same, so it is not on the graph.
    • C. The temperature outside Not this one. Temperature was not measured in this test.
    • D. How much water each cloth held Not this one. Both held about the same at the start. The axis shows time.
  5. Question 5 of 5Rahul did the test once. What should he say?

    See the answer and why
    • A. "Shade dries clothes faster." Not this one. That is the opposite of what his test showed.
    • B. "In my test, the sun cloth dried faster. I could repeat it to check." Correct. One test is real evidence, but repeating shows whether it happens again.
    • C. "Cloth in the sun dries faster every time, everywhere." Not this one. One test cannot show "every time, everywhere".
    • D. "My test proves nothing, so ignore it." Not this one. One test is real evidence. It is just not enough on its own for a rule.

Think back

What could have made your test unfair?

Would the result be the same on a cloudy day?

Investigate further

  • Test a cloth hung flat against a cloth hung folded. Which dries faster?
  • Test on a windy day and a still day. Does wind change the time?

For grown-upsTap a heading to open it. The safety notes are at the top of the page.

Before you start
  • Two same-size cloths, pegs and a line in both a sunny and a shady spot.
  • Plan for about an hour and a half on a sunny day.
Questions that help
  • "What did we keep the same? Why?"
  • "Would the answer be the same tomorrow?"
What's really going on

Warmth from the sun speeds up evaporation, so cloths usually dry faster in sun, but wind, humidity and the cloth also matter.

The key habit here is changing one thing at a time and saying what one test can and cannot show.

Other ways to do it
  • No sun? Compare a cloth near a fan with one away from the fan.

For teachersLearning aims, classroom ideas and what to look for.

Learning aims
  • Carry out a simple fair comparison.
  • Present results as a bar graph with a title, labelled axes and an even scale.
Subject links
  • Science: evaporation and fair testing.
  • Mathematics: bar graphs and time.

These links are general. They have not been checked against a specific board syllabus.

In the classroom
  • Groups run the same test; pool results on one class bar graph and discuss differences.
What to look for
  • Names the one thing changed and things kept the same.
  • Draws an even scale and labels both axes.
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