We might have experienced this: on a hot summer evening, after school when we were about to ride home, we found that the bicycle tire had burst after being exposed to the sun. Although this is a minor matter, it ruined our good mood for the whole day. Why does a bicycle tire burst?
Any object has the characteristics of thermal expansion and contraction. For example, when boiling water in a kettle, the water in the kettle cannot be filled too full, otherwise the water will overflow due to volume expansion after heating. Through careful observation, we will find that the water in the kettle is not static when boiling. The water at the bottom of the kettle expands after heating and has a lower density than the water above, so it flows upward. Similarly, in the hot summer, when we enjoy a refreshing ice cream, we will find that there is "cold air" flowing down around the ice cream. This is because the air close to the ice cream cools down and contracts, making it heavier than the surrounding air, so it flows downward.
In summer, not only the air is hot, but also the ground is scorching under the sun. Under the sun's exposure, the air in the bicycle tire expands and constantly presses against the tire. If the air in the tire is too full or there are weak spots in the tire, it will burst the tire. Experienced people tell us that to avoid bicycle tire bursts in summer, we should not overinflate the tire. If the air in the tire is too full, we should release a little to leave room for gas expansion. Not only bicycles, but car tires also have the same problem, so we should do a good job of maintaining car tires in summer.
The essence of gas thermal expansion and contraction lies in the microscopic gas molecules constantly doing thermal motion. The higher the temperature of the gas, the more intense the thermal motion, and the weaker the binding force between the gas molecules, resulting in an increase in the average distance between the gas molecules and an increase in the macroscopic volume. For gas in a fixed volume, an increase in temperature will lead to an increase in gas pressure. This is also the reason why high temperatures can cause tire bursts.
There are many ingenious applications of the principle of gas thermal expansion and contraction in life. If you accidentally crush a ping-pong ball, you can put the ping-pong ball in a bowl of hot water, and the ping-pong ball will soon become round again. This is because the air in the ping-pong ball expands after heating, making the ping-pong ball round again.