argumentative writing

On Sunday, after finishing my homework, I have nothing to do, so I want to play with soap bubbles. I mixed the soapy water, soaked the plastic pipe in a small bottle filled with soapy water, and then blew it gently with my mouth. A string of bubbles flew out of the plastic pipe, colorful and beautiful. I blew harder and harder, blowing over and over again, and soap bubbles kept coming out, as if it had rained with soap bubbles. Suddenly found a problem: a string of soap bubbles always rises gently first, and then falls slowly. What's going on here? Has the quality of soap bubbles changed?

I put this question to my mother. Mom thought for a moment and said, "well ... I think it's the same principle as a hot air balloon." Is that really the case? I know that hot air balloons can fly into the sky because of the hot air generated by fuel combustion, but is there hot air in the soap bubbles?

In order to find out this problem, I rummaged through all the books at home and finally found the answer in a book "100,000 Why": when we blow soap bubbles, the soap bubbles are full of the gas we blow in. Unless it is very hot weather, the gas we exhale is always hotter than air. The quality of hot air is light, so the soap bubbles just blown out will rise upwards; However, with the passage of time, the temperature of the gas in the soap bubble drops, the volume of hot air shrinks, and the soap bubble gradually becomes heavier than air, so it has to fall slowly.

Haha, it turns out that my breath is the fuel of soap bubbles.