States of Matter - Solids, Liquids and Gases

Objective: Describe the effects of temperature and pressure on the volume of a gas

Introduction

Matter exists in different states, the most common being solid, liquid, and gas. The particles in each state have distinct arrangements and behaviors. This section focuses on the properties of gases and how their volume is affected by changes in temperature and pressure.

Properties of Gases

Gases have the following key properties:

• No definite shape: Gases take the shape of their container.
• No definite volume: Gases can expand to fill the available volume of their container.
• Compressible: Gases can be easily compressed by applying pressure.
• Diffusible: Gases readily mix with each other.

Effect of Temperature on the Volume of a Gas

Charles's Law: This law states that the volume of a gas is directly proportional to its absolute temperature, provided the pressure and the amount of gas remain constant. In simpler terms, as the temperature of a gas increases, its volume increases. Conversely, as the temperature decreases, the volume decreases.

Mathematically, Charles's Law is expressed as:

$$ \frac{V_1}{T_1} = \frac{V_2}{T_2} $$

Where:

• $V_1$ = Initial volume of the gas
• $T_1$ = Initial absolute temperature of the gas (in Kelvin)
• $V_2$ = Final volume of the gas
• $T_2$ = Final absolute temperature of the gas (in Kelvin)

Explanation: When the temperature of a gas increases, the gas particles move faster and collide more frequently with the walls of the container. This increased kinetic energy results in the gas expanding to occupy a larger volume.

Effect of Pressure on the Volume of a Gas

Boyle's Law: This law states that the volume of a gas is inversely proportional to the pressure exerted on it, provided the temperature and the amount of gas remain constant. In simpler terms, as the pressure on a gas increases, its volume decreases. Conversely, as the pressure decreases, the volume increases.

Mathematically, Boyle's Law is expressed as:

$$ P_1 V_1 = P_2 V_2 $$

Where:

• $P_1$ = Initial pressure of the gas
• $V_1$ = Initial volume of the gas
• $P_2$ = Final pressure of the gas
• $V_2$ = Final volume of the gas

Explanation: When the pressure on a gas increases, the gas particles are forced closer together, reducing the available space and thus decreasing the volume.

Summary Table

Property	Effect on Volume	Law
Temperature	Directly proportional: Volume increases with increasing temperature	Charles's Law
Pressure	Inversely proportional: Volume decreases with increasing pressure	Boyle's Law

Applications

The principles of Charles's Law and Boyle's Law are applied in various real-world situations, such as in the design of submarines, engines, and pneumatic systems.