Absorption and emission of heat. Fun physical experience at home

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Absorption and emission of heat. Physical experiments

Entertaining experiments in physics

Entertaining experiences at home / Physics experiments for children

Let's make experiments that will clearly show that the black surface absorbs and radiates heat rays more strongly.

Take a medium sized metal can. Attach a square of white paper on its outer side with adhesive tape, and on the opposite (also outer) side, attach a square of paper of the same size, but painted on both sides with black ink.

Then take two nickels and put in the middle of each of them an identical small, pea-sized piece of stearin candle. Holding the coin with pliers, bring it to the flame of a candle or gas stove. As soon as the stearin melts, tilt the coin in different directions so that the stearin covers its surface with a thin layer. After turning the coin over, attach it to the middle of the white square and press it against the jar with a rag. Let the stearin harden and when the coin holds, glue the second nickel to the middle of the black square in the same way.

Absorption and emission of heat

When everything is ready, pour boiling water into the jar to the very top and watch what happens to the coins.

At first, a coin from a black square will disappear quite quickly, and after a few seconds another coin will also disappear from a white piece of paper.

The conditions for the coins were created exactly the same, the difference was only in the color of the surfaces of the paper squares with which they were glued to the bank. The black square heated up faster than the white one, and the coin fell off earlier.

Glued coins, of course, will not, like pieces of paper, fit the surface of the tin can and stick with their middle part, in diameter. But it is important that the stearin covers the coins with a uniform thin layer: the coins must be glued in exactly the same way.

After the experiment, remove the remains of stearin from the coins and wipe them well with a rag.

And now let's move on to the experiment with the radiation of heat. Wrap two identical glasses with white paper and seal it along the seam. Paint the outside of one of the glasses with black ink. Warm the glasses with water (carefully so as not to soak the paper), place them on the table at some distance from each other and pour very hot water from the kettle into them to the very brim. For this experiment, you will need a thermometer to measure the temperature of the water (but without a case).

Absorption and emission of heat

Glasses filled with hot water are in the same conditions, the difference between them is only in the color of the wrappers. If you immediately, as soon as you filled the glasses with water and put them on the table, measure the temperature of the water in them, then make sure that it is the same.

Take the next temperature measurement after a while, fifteen minutes later. You would notice that in the black glass the water has cooled down more. For example, if the temperature in a white glass is 48°, then in a black glass it is 47°. Although the difference is small, only one degree, but this is enough to make sure that the water in the black glass cools faster. Always keep the thermometer at a fixed level. Rearranging the thermometer from one glass to another, you will notice how the alcohol or mercury column of the thermometer either rises or falls by that same one degree difference in temperatures.

Of course, the experiment could be more visual if the glasses were closed on top with white and black lids, and identical thermometers were inserted into them. But let us be content with our modest observations. (By the way, everything will turn out just as well if you take two identical cans, one of which is covered with soot.)

Author: Rabiza F.V.

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