Particle Model & pressure

• What is the state of molecules in a gas according to the kinetic theory?

  Molecules in a gas are in constant random motion at high speeds
• How is the temperature of a gas related to the kinetic energy of its molecules?

  The temperature of the gas is related to the average kinetic energy of the molecules
• What happens to the average kinetic energy of a gas as its temperature increases?

  The hotter the gas, the higher the average kinetic energy
• What is the effect of cooling a gas on its average kinetic energy?

  The cooler the gas, the lower the average kinetic energy
• What does random motion of gas molecules imply?

  Random motion means that the molecules are travelling in no specific path
• What is Brownian motion?

  The random motion of tiny particles in a fluid is known as Brownian motion
• How does the motion of gas molecules change with temperature and pressure?

  The motion of molecules in a gas changes according to the temperature and pressure of the gas
• What happens to the average speed of gas molecules as temperature increases?

  As the temperature of a gas increases, the average speed of the molecules also increases
• What is the relationship between kinetic energy and the speed of gas molecules?

  The kinetic energy of the molecules also increases if its volume remains constant
• How is pressure defined in the context of gas molecules?

  Pressure is defined as the force exerted per unit area of the container
• What effect does high pressure have on gas molecule collisions?

  A gas at high pressure has more frequent collisions on the container walls

  
• What happens to gas molecules when the gas is heated?

  If the gas is heated up, the molecules will travel at a higher speed
• How does an increase in temperature affect the pressure of a gas at constant volume?

  An increase in temperature increases the pressure of a gas at constant volume
• What is the relationship between pressure and volume in a gas at constant temperature?

  • If the temperature of a gas remains constant:
  • Compressed gas: decreases volume, increases pressure
  • Expanded gas: increases volume, decreases pressure
• What happens to the pressure of a gas when it is compressed?

  The pressure increases when a gas is compressed
• How does the net force produced by pressure act on the walls of a gas container?

  The pressure produces a net force at right angles to the wall of the gas container
• What occurs when gas molecules hit the walls of a container more frequently?

  This creates a larger overall net force on the walls which increases the pressure

  
• How does changing pressure affect the volume of a gas at constant temperature?

  • Increasing pressure compresses the gas, decreasing its volume
  • Decreasing pressure allows the gas to expand, increasing its volume

  
• What happens to the density of a gas when it is compressed?

  The density of the gas increases, allowing more frequent collisions of the molecules on the container wall

  
• What is Boyle's Law?

  • For a fixed mass of gas at constant temperature:
  • \( pV = \text{constant} \)
  • Pressure and volume are inversely proportional

  
• What is the equation relating pressure and volume before and after a change in a gas?

  \( P_1 V_1 = P_2 V_2 \)

  
• If a gas occupies a volume of $0.70 \text{ m}^3$ at a pressure of $200 \text{ Pa}$, what is the pressure when compressed to $0.15 \text{ m}^3$?


  Pressure increases due to compression
• What should you check after calculating the final pressure of a gas?

  Always check whether your final answer makes sense

  
• What happens to the temperature of a gas when work is done on it?

  • Work done on a gas increases its internal energy
  • This can also cause an increase in temperature
• How does compression affect the kinetic energy of gas molecules?

  Compression causes the molecules to move around faster and have a higher kinetic energy
• What happens to the temperature of a gas when it expands?

  When a gas expands, it loses energy, resulting in a decrease in temperature
• What is an example of work done on a gas that increases its temperature?

  • A bicycle pump compressing gas
  • The pump gets warm due to work done on the gas
• What happens when pressurized carbon dioxide is released from a high-pressure cylinder?

  • The gas does work, losing energy
  • This can cause the carbon dioxide to freeze, forming dry ice
• What is the effect of work done on a gas versus work done by a gas?

  When work is done on the gas, the temperature rises; when work is done by the gas, the temperature falls
• How can students visualize the concepts of work done on gases?

  • Act out gas particles moving and colliding
  • Demonstrate compression and expansion in a controlled environment