🌡️ Does a cover keep water in the sun warmer?

My hypothesis

If I change what covers the water, then how many degrees the water warms in one hour will ______, because ______.

🔊 You fill in the blanks. Think about what each cover does to the sun's light, and to the warmth that tries to get out. A guess is a good because: the test finds out.

Change, measure, keep the same

Scientists call the thing you change the independent variable and the thing you measure the dependent variable. The things you keep the same are the controls: if one of them changed too, you wouldn't know which change made the difference. Try each of the 4 levels 3 times.

What you need

• 🥛 Clear plastic cups, all the same size: 12, all the same size
• 🚰 Water from the tap
• 🌡️ A thermometer (digital, or the red-liquid kind)
• 🎞️ Clear plastic wrap
• 🥈 Foil
• 🟨 Construction paper: black, white, red, blue and yellow: black
• 🩹 Masking tape, to mark lines
• 🍽️ A baking tray or big plate
• ⏱️ A stopwatch or a kitchen timer
• ✂️ Kid scissors

Steps

1. Pour the same amount of cool tap water into twelve clear cups, about halfway.🔊
2. Dip the thermometer in one cup and write down the starting temperature.🔊
3. Cut nine wraps big enough to cover a cup's top and sides: three plastic wrap, three foil, three black paper.🔊
4. Wrap three cups in each kind, and tape each wrap down on one side only so you can lift a flap.🔊
5. Leave the last three cups with no cover.🔊
6. Carry all twelve cups on a tray to one sunny spot on the ground, side by side, and start the timer.🔊
7. Never look at the sun: look down at your cups.🔊
8. Every 15 minutes, lift the flap on one cup of each kind, read its water and write it in your log.🔊
9. After one hour, quickly read the water in all twelve cups and write each number down.🔊
10. Take away the starting number to find how many degrees each cup warmed.🔊
11. Find the mean warming for each cover and draw a bar graph.🔊

Every step is one you can do yourself, with a grown-up nearby. Write each number down straight away, in the table below, so nothing is lost.

Your results table

From 4th grade, add the tries for each level and divide by how many there were: that's the mean, and it goes in the last column. Then draw a bar graph, one bar for each thing you tried.

Why it works

🔊 Sunlight carries energy, and things in the sun warm up as they soak it in. Clear plastic wrap lets light in but slows warm air and water vapour from escaping, so the water under it often warms well. Black paper soaks up light and turns it into warmth, while shiny foil bounces much of the light away, so the water under it often stays cooler.

Going further (7th and up): Change a second thing: put the covered cups in the shade as well as the sun, and graph the warming for each cover in both places.

Board layout

This project at your grade

From 4th grade up, the table gets a mean column. See every project for 3rd grade, or print a blank results table.

What a judge will ask

• What did you change, and what did you measure? I changed what covers the water and measured how many degrees the water warms in one hour, in degrees.
• What did you keep the same, and why does that matter? I kept the same amount of cool tap water in every cup and the same kind of cup the same, so the only difference was what covers the water.
• How many times did you test it? 3 times at each of my 4 levels.
• If you did it again, what would you change or test next? I'd put the covered cups in the shade as well as the sun, and graph the warming for each cover in both places.

Make it yours

Keep this project on this device and Peabody counts down to your fair day, with a plan for each day. Nothing is sent anywhere.

Try next

• 🌡️ Which colour of paper warms up most in the sun?3rd–8th grade · 1 day of testing · about $3🌦️ Growing and weather · 🌱 Outside and plants
• ☀️ Where does a puddle dry fastest: sun, shade or wind?2nd–6th grade · 2 days of testing · free🌦️ Growing and weather · 🌱 Outside and plants