Why do metals heat up in the sun?

At some point we have all made the mistake of going to pick up something that has been left lying in the sun for too long. Sometimes, it will be too hot to hold for long. Some objects heat up far quicker than others. Some hardly heat up at all. For example, metal objects are often the hottest to touch. Why do objects heat up like this? Why are some objects more likely to heat up than others?

HOW DOES THE SUN PROVIDE HEAT?

The surface of the sun is 5500oC. That is almost one hundred times the highest recorded temperature on Earth. This means that the sun has a lot of energy, which we call solar energy. Solar energy travels through space until it reaches the earth. The sun is 150 million kilometres away from the Earth. The solar energy that reaches the Earth is in two major forms – visible light and thermal energy. The visible light lights up the day. The thermal energy warms up the Earth. The brightness and heat of the sun can change – this is because of many reasons.  For example, when there are lots of clouds in the sky, they can block thermal energy before it reaches the ground.

WHY DO OBJECTS HEAT UP IN THE SUN?

The thermal energy from the sun heats up the air, the ground and other objects. All material is made up of small particles called atoms. When energy from the sun hits an object its atoms are heated up. When atoms are heated they move and bump into other atoms. This transfers some of their energy to them. This is how heat spreads through an object.

WHY DO SOME MATERIALS HEAT UP MORE QUICKLY?

Metal heats up much more quickly than many other materials. This is because metals are good heat conductors. Good conductors are materials that heat spreads through quickly.

All materials are made of small particles. These small particles are called atoms. Atoms are made up of even smaller particles called protons, neutrons and electrons. Protons and neutrons form the centre of an atom. This structure is called the nucleus. Electrons move around the nucleus like the moon orbits the Earth.

Multiple atoms are held together by bonds. Metals are held together by metallic bonds. Metallic bonds allow electrons to flow freely through the material, instead of being held close to the nucleic of the atoms. This allows heat to be transferred quickly through the material.

The opposite of a conductor is an insulator. An insulator does not transfer heat efficiently.

The colour of a material also influences their conductivity. Black materials will conduct heat faster than white materials.

So, next time it’s a really hot day, try wearing a white T-shirt instead of a black one. You might notice that you don’t warm up as quickly as you would otherwise!

RHIAN GRUER

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