Charles' Law Experiment | Gas Laws | Class 9 | CBSE | NCERT | ICSE

Summary

The video explains the relationship between speed, distance, and frequency of boundary hits, using a running person as an analogy. It then transitions into Charles' Law, where a scientist named Charles conducted an experiment in 1787 to demonstrate that the volume of gas is directly proportional to its temperature at constant pressure. The law is illustrated using examples and experiments, showing how volume increases with temperature and decreases when cooled, as demonstrated through a plastic bag deflating in a freezer and inflating when heated. The video concludes with a mathematical example of applying Charles' Law.

Takeaways

• 🏃‍♂️ A person running at double speed hits the boundaries double the number of times within the same time frame.
• 📏 To limit the number of boundary hits while running at double speed, the person must cover a greater distance, specifically double the original distance.
• 💡 Charles' Law experiment demonstrates how the volume of gas increases with temperature when pressure is kept constant.
• 🔥 The capillary tube in Charles' experiment shows that as temperature rises, the volume of gas increases, and as temperature decreases, the volume decreases.
• 🔬 Charles' Law states that at constant pressure, the volume of a gas is directly proportional to its temperature (in Kelvin).
• 📊 A graph of volume vs. temperature at constant pressure (isobar) shows a linear relationship, where volume increases as temperature increases.
• ❄️ Absolute zero (0 Kelvin or -273°C) is the temperature at which molecular motion ceases and the volume of gas becomes zero.
• 🔍 The formula V1/T1 = V2/T2 is used to calculate changes in volume and temperature for a gas at constant pressure, based on Charles' Law.
• 🌡️ In an example, cooling a gas at 300K to reduce its volume to one-third results in a final temperature of 100K.
• 🎈 A practical example of Charles' Law: a plastic bag filled with air deflates when cooled and reinflates when heated, demonstrating the direct relationship between gas volume and temperature.

Q & A

What happens to the number of times the person touches the boundaries when their speed is doubled?

When the person's speed is doubled, they touch the boundaries double the number of times in the same time period.

How can the person touch the boundaries only eight times when running at double speed?

The person can touch the boundaries only eight times at double speed by covering double the original distance.

What is the main observation from Charles' experiment with the gas in the capillary tube?

Charles observed that as the temperature of the water bath increased, the volume of gas trapped in the capillary tube increased, and when the temperature decreased, the volume of gas decreased, while pressure remained constant.

What does Charles' Law state?

Charles' Law states that for a particular gas, if the pressure is kept constant, the volume of the gas is directly proportional to its temperature.

What is the relationship between speed and distance in the context of the running person analogy?

In the analogy, the speed of the person is compared to temperature, and the distance they cover is compared to the volume of gas. Greater speed (temperature) leads to covering a greater distance (increased volume), with the number of boundary hits (pressure) remaining constant.

Why do we use the Kelvin scale in Charles' Law calculations?

We use the Kelvin scale in Charles' Law because it is the absolute temperature scale, where 0 K represents the point where all molecular motion ceases, and it's essential for accurate temperature-volume proportionality calculations.

What happens to the volume of a gas at absolute zero temperature according to Charles' Law?

At absolute zero (0 K), the volume of the gas becomes zero because the particles no longer move, and molecular motion ceases entirely.

What kind of graph is obtained when plotting volume against temperature for Charles' Law?

A straight-line graph is obtained when plotting volume against temperature at constant pressure, showing that volume increases as temperature increases.

What is the significance of the -273°C value in the context of Charles' Law?

-273°C corresponds to 0 K, which is absolute zero, the temperature at which the volume of any gas would theoretically become zero.

How does kinetic energy affect the volume of gas in Charles' Law?

As temperature increases, the kinetic energy of the gas particles increases, causing them to move faster and hit the container walls more often. This increases the volume of the gas, assuming constant pressure.