HEAT TRANSFER by Brad Litchfield

Heat can be transferred by radiation. Radiation is the transfer of heat through empty space by waves. In class, we did an experiment with a black can, a silver can, and a lamp. We put water in each can and lit the lamp, recording the temperature of the water in each can as time went on. We left the lamp shining on the cans for 10 minutes then recorded the results. The temperature of the water in the black can was greater than the temperature of the water in the silver can. This tells us that different colors absorb heat differently. For example, the black can’s water had a greater temperature because the color of the black can absorbs all of the heat. The silver can’s water wasn’t as hot because the silver color doesn’t absorb all the heat that black does, that’s why it’s a lighter color, not dark, like black.
Because different materials and colors absorb heat differently, the Earth’s surfaces are also heated differently. Because of this, dark surfaces get hotter faster than light surfaces. This is why water heats slower than land, because it is a lighter surface.
The weather on Earth is also caused by radiation. The Sun warms the planet, drives the hydrologic cycle, and makes life on Earth possible. The amount of sunlight received on Earth’s surface is affected by the reflectivity of the surface, the angle of the Sun, the output of the Sun, and the cyclic variations of the Earth’s orbit around the Sun.

  Electromagnetic spectrum            Sun heating the Earth by radiation
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Heat can also be transferred by conduction. Conduction is the transfer of heat by physical contact, or solids. When heat is being transferred from an object to another, the molecules start heating up, which makes them move faster. It starts off as the heat source making molecules near it move faster, which makes molecules near those molecules move faster, and so on, until the whole object’s molecules are moving faster and the object is hotter. One day in class, we watched a video called Eureka. In the video, there were witches with broomsticks stirring a pot of hot liquid. The witches all burnt their hands because of the conduction that was happening. The hot liquid was heating the broomsticks which had that ripple effect and made all the molecules in the broomsticks speed up and get hotter. Conduction also has a role in the weather on Earth. Conduction refers to how well a substance absorbs heat & lets it go. So, for instance, water (oceans, lakes) take a long time to heat up & cool down. They in fact will regulate the temperature in areas so that in the winter it is warmer (vs. same latitude places) and in the summer it's cooler. Air molecules will conduct through different surfaces differently. The surface needs to be able to have the molecules speed up when bumped into by other speeding molecules to make it warmer.

Conduction transferring heat from source to hand             Conduction in the atmosphere.
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Convection is the transfer of heat by liquids and solids that flow. An example of this is the outer core heating the mantle. The outer core, which is a liquid heats up and also heats the mantle, which is a solid that can flow. Changes in temperature and density happen when convection is occurring. Warm, less dense air rises and cooler, denser air sinks, causing winds to form. Another thing we did in class was the smoke box lab. For the smokebox lab, we had a box with two tubes sticking out of the top of it. There was a lit candle and also incense inside of the box. What happened was the smoke rose out of the right tube, but not the left tube. This is because the warm air and smoke, which is less dense was being pushed by the cold, more dense air, which was sinking into the left tube. The cold air sank into the left tube and the warm smoke rose out of the right tube. It was cool because you could see the convection currents of smoke in the box. Convection also plays a role in the Earth’s weather. Due to its role in heat transfer, natural convection plays a role in the structure of Earth's atmosphere, its oceans, and its mantle. Discrete convective cells in the atmosphere can be seen as clouds, with stronger convection resulting in thunderstorms.

      Smoke box lab Convection currents in the atmosphere
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