Observe: Ouch, That Sand is Hot!

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Various surfaces and substances absorb heat from the Sun differently.

The Sahara is the biggest desert in the world; it covers most of Northern Africa. It is also one of the hottest and driest areas of the world. If you have ever tried to walk across a beach on a hot day in your bare feet, you can imagine what it would be to walk in the Sahara on a sunny day!

Many people do not know that a desert gets very cold at night. Sand heats up quickly in the Sun, but dry sand does not hold heat energy well. It cools very fast when the sun sets.


Even on the hottest day at the beach, the water stays cool.

If you do get hot feet at the beach, you can always step into the water. However, why does the Sun heat up the sand so much and not the water?

The answer has to do with heat capacity.

Water has a very high heat capacity; dry sand has a very low heat capacity. Although the water on the beach receives the same energy from the Sun as the sand does, the water does not increase much in temperature. High heat capacity substances such as water need to gain or lose much more heat to change their temperature. You could say that a high heat capacity substance resists temperature change. Substances such as dry sand have low heat capacity. With only a small amount of heat gain or loss, dry sand changes its temperature.

Heat capacity is linked closely to weather patterns. For example, hot days on the Sahara cause fast-rising air that can lead to stormy weather. Hot, rising, spinning air from the Sahara is carried west by the wind, and it can travel all the way across the Atlantic Ocean to become strong hurricanes that strike North America.

In the next activity, you will observe exactly how various surfaces and substances hold heat differently.

  Video

Watch the ADLC Digital Lesson: Heat Capacity before starting the activity. This is a demonstration of how temperature of different substances changes different amounts when exposed to equal heating.


Do various substances and surfaces hold heat differently?

Materials

  • ADLC Video – Heat Capacity
  • Temperature Change Graph
  • Heat Capacity of Substances chart

    Notebook

    Click here to download the instructions for this activity. Save to your Weather Notebook.

      Cultural Connection

    The Tuareg people of North Africa live in the Sahara desert. The men wear a piece of fabric on their heads called a tagelmust. Tuareg men cover their faces with the tagelmust as excellent protection from sandstorms. The head covering keeps the head cool in the Sun and warm at night.