How to tell temperature by using molecular motion - Middle School 1st grade - 2nd semester

한글

Do you know what 'molecules' are? In the dictionary, it is 'the smallest particle that an object can have.' Well, this thing called 'molecule' also exercises, and we can know what the temperature is, by using how much the molecule's exercising is lively.

First, molecular motion is divided into three groups - molecular motion when the condition is different, molecular motion when the temperature is different, and molecular motion when the condition and temperature are all different. Now, let me tell you about molecular motion when the condition is different. Let's look at a chart to understand it easily.

From this, we can understand that when the condition is different, the activity of molecular motion is

Solid matter < Liquid < Gas

Now, let's look at why this is in this order. Oh, and remember that all molecules exercise.

Many molecules are listed in a perfect line and they all want to move. When they try to move, there are all these other molecules blocking the way.

⇒ vibratory motion

On the other hand, in this part, the molecules are bit separated. So they move, but they are still close.

⇒ bit lively motion

Lastly on this part, all the molecules are very far and there are enough space to move very fast.

⇒ lively motion

and let's present this in picture.

Next is molecular motion when the temperature is different. Let's look at the drawing.

The girl in the first picture is looking very happy, in a warm place. Meanwhile, the girl in the second picture is curing up, because the weather is so cold. Molecules are the same as this. They act more wildly when the temperature is higher. And this is related to Charles's law. For example, I will say there is a crushed ping-pong ball. Inside the ball, there are molecules. Well when we put the crushed ball in the boiling water. it gets to it's original state, because molecules acted wildly.

Lastly, we will learn about molecular motion when the condition and temperature are all different. When we put higher temperature to solid matter, liquid, and gas, solid matter does more lively vibratory motion, and liquid and gas does more lively motion.

Charles's law - Middle School 1st grade - 2nd semester

한글

Charles's law, otherwise known as Charles and Gay-Lussac's law. It's meaning in dictionary means the gas volume gets 1/273 bigger as temperature gets 1℃ higher. Easily, as temperature rise, molecular motion gets active, so volume gets bigger. But, we say 1/273 in accurate number. Using Charles's law, we can put a crushed ping-pong ball back into its original state. Let's look at an example.

<other examples using Charles's law>
Why does a snack pack inflate in hot summer? Let's investigate about the reasons why.

In a snack pack, there is gas called 'Nitrogen'. Before that, why is this 'Nitrogen' inside the pack, instead of oxygen?

You might have seen iron go rusty, or wine get all sour. This situation is called "oxidation response". Like this, if oxidation response happens, the material's properties change. Snacks are mostly food deep-fried so it go bad easily, but nitrogen help reduce chemical reaction and help save snacks. Anyway, when you look at the meaning of Charles's law, you can see that it says 'regardless of kind'. Therefore, the snack pack filled with nitrogen inflates because it's summer and temperature rise. Outside of that, if you put a rubber balloon in hot water, it gets bigger and when you heat air in a hot-air balloon, it floats. These are all connected to Charles's law.

<Let's do a experiment together!>
A good experiment to understand Charles's law is peeing doll experiment.

<Supplies>
a peeing doll, cold & hot water, a tank to get water.
*It's better if the cold and hot water's temperature's gap is large.

First, put the doll in hot water to get rid of air inside the doll. Then, put the doll inside the cold water. Lastly, put the doll in the tank and pour hot water over its head.

Let's talk about the scientific knowledge we can learn through this experiment. First, if you put the doll in hot water, temperature will rise and gas volume will get bigger. Next, when you put the doll  in the cold water, the doll's inside pressure gets weak, so water can get in the doll. Lastly, when you pour hot water back on the doll, the inside pressure gets higher, and water comes out from the doll.

→ When the temperature is low, gas volume decrease, and when the temperature rise, gas volume increases.