Test: Study Of Gas Laws - Class 9 MCQ

The kinetic molecular theory states that gases are made up of molecules that are in constant random motion. This movement explains many properties of gases, including their ability to fill the shape and volume of their containers. The theory emphasizes that gas molecules move freely and do not have fixed positions.

A decrease in external pressure at constant temperature allows gas molecules to spread out more, resulting in an increase in volume. This behavior is described by Boyle's Law.

Gases have lower density compared to liquids and solids because they consist of fewer molecules per unit volume. This is primarily due to the large intermolecular spaces that exist in gases, allowing them to expand and fill any container.

The kinetic energy of gas molecules is directly proportional to the absolute temperature. As temperature increases, the kinetic energy of the molecules also increases, leading to greater molecular motion and more frequent collisions.

According to Charles's Law, at constant pressure, the volume of a gas increases as temperature increases. This is due to the increased kinetic energy of the molecules, which causes them to move faster and push apart, thereby expanding the volume.

Charles's Law states that at constant pressure, the volume of a given mass of gas is directly proportional to its absolute temperature (in Kelvin). This means that as temperature increases, volume also increases, and vice versa.

When gas is collected over water, the total pressure includes both the pressure of the dry gas and the vapor pressure of the water. Therefore, the actual pressure of the dry gas is calculated by subtracting the vapor pressure from the total pressure. This shows that moisture reduces the effective pressure of the gas.

Absolute zero is the theoretical lowest temperature at which all molecular motion ceases. It is defined as 0 K or -273°C, and at this temperature, gas molecules would have no kinetic energy.

Molecular motion theoretically stops at absolute zero, which is -273°C (or 0 K). At this temperature, particles have minimal energy and are in their lowest energy state, leading to no movement.

To calculate how the volume of a gas changes with temperature while maintaining constant pressure, Charles's Law is the appropriate choice. It shows the direct proportionality between volume and absolute temperature.

Boyle's Law is significant because it explains how increasing pressure leads to a decrease in volume, which means that at high altitudes, where atmospheric pressure is lower, the density of air decreases. This results in less oxygen available for breathing, necessitating the use of oxygen cylinders by mountaineers.

Standard temperature and pressure (S.T.P.) is defined as 0°C (273 K) and 760 mm Hg (1 atm). This standard is used for comparing gas volumes under consistent conditions.

The significance of using the Kelvin scale in gas law calculations is that it ensures all temperature values are positive. This is crucial because gas laws rely on absolute temperature for accurate calculations, and negative temperatures are not valid in these contexts.

Following Charles's Law, if the temperature of a gas decreases while maintaining constant pressure, its volume will also decrease. This occurs because lower temperatures result in reduced molecular motion, causing the gas to occupy less space.

Liquefaction occurs when gas molecules lose energy (due to cooling) and are subjected to increased pressure, causing them to come closer together and transition into a liquid state. This process demonstrates the interplay between temperature and pressure in determining the state of a substance.