☰ Year plan · Science

Sand, water and the forecaster’s tools

Week 20 · Unit 3: Concept 3.2 (B): heating of sand and water, rising warm air, forecasting tools · 3 lessons
1

Sand or water: which warms up faster?

Science P6: Term 2, Unit 3, pp. 26–31
GoalCompare how fast sand and water warm up and cool down, and explain why seaside places have milder weather.
New words
temperature · how hot or cold something isinvestigation · a fair test to answer a questionmild · not too hot and not too cold
Explanation

Which warms up faster in the Sun, a tray of sand or a tray of water? Let us investigate. A grown-up puts the same amount of dry sand in one tray and water in another and sets both in the sun with a thermometer in each. We read the temperatures every ten minutes. The sand gets hotter much faster. Then we move both trays into the shade: the sand also cools faster, while the water changes slowly. So land and sand heat up and cool down faster than water. Water is the opposite: it warms and cools slowly. This is why places near the sea have milder weather: the sea warms slowly in summer and cools slowly in winter, so the air nearby is not so hot or so cold. Our model leaves out waves, the depth of the sea, and the mixing of water.

010203040010203040°Csandwater
Worked examples
StartAfter 40 minutesChange
sand223513
water22264
Mariam’s graph shows that after forty minutes in the sun the sand is 13 degrees warmer than at the start, while the water is only 4 degrees warmer.
Karim says: the sand must heat up slower because it is solid. Mariam checks the graph. The line for sand climbs more steeply. The sand heats faster.
beachsea
At the beach in the afternoon, the sand is too hot to walk on barefoot, but the sea feels cool. In the evening the sand cools quickly and the water is still warm.
Class activity

Sand and water. With a grown-up, put equal amounts of dry sand and water in two shallow trays in the sun. Put a thermometer in each (not touching the bottom) and read every ten minutes for forty minutes. Then move them into the shade and keep reading. Draw a line graph. Never look at the Sun. Remember the sand: it can be hot.

Practice
1
Which warms faster in the Sun, sand or water?
2
Which cools faster in the shade, sand or water?
3
Why do places near the sea have milder weather?
4
Name something our model leaves out.