Resources: The presentation and mini whiteboards.
Support Handout: Page 1; a series of questions on gas pressure.
Core Handout: An activity for the students to investigate the relationship between the force applied (which is directly proportional to pressure) and the volume of gas. A comprehension task is also included.
Use the previous lesson from the unit to recap on the behavior of particles in matter, such as their movement and the space between them.
Ask the students to discuss and create a list of matter which can easily change from solid, to liquid and then to gas.
Use the presentation slides to explain what causes gas pressure and how this can be increased by increasing the temperature or decreasing the volume. The students will then carry out an investigation into how changing the force (pressure) affects the volume of gas. Force is directly proportional to pressure, and for the challenge task, the students can calculate the pressure for each force using the equation on the handout.
Career Film: Take a tour around the offices of the Nuclear Decommissioning Authority (NDA) in Cumbria to find out about Mark Wareing's job. Mark works as a Programme Manager for NDA.
Expert Film: This is Mark Wareing. Mark works as a Programme Manager for Nuclear Decommissioning Authority. Listen to Mark as he talks about gas pressure using a particle model.
Ask the students to investigate the relationship between the force applied and the volume of gas.
1. Mount the syringe in a clamp stand with the plunger upright.
2. Pull the syringe back and forth a few times to ensure the plunger doesn’t stick to the sides of the tube. Let the plunger settle and record the volume of gas in the syringe.
3. Place a slotted mass on the top the plunger (you can use another clamp to stabilise the slotted mass). Record the volume of gas in the syringe.
4. Continue adding slotted masses on top of the plunger and recording the volumes.
Once complete, the students should plot their results as a scatter plot with a line of best fit and then draw a conclusion from their graph.
Support: The first sheet on the handout provides questions to help the students understand gas pressure.
Challenge: The students should calculate the pressure inside the syringe with different forces applied and can then state the relationship between pressure and volume.
Using the students’ results, discuss the observations and conclusions that they made.
Particle Model Reminder: Begin by reminding students about the particle model of matter, emphasising that gases are made up of tiny particles that are constantly moving and colliding with each other and the walls of their container.
Particle Motion and Pressure: Explain that gas pressure is caused by the collisions of gas particles with each other and the container walls. Emphasise that the more frequent and forceful the collisions, the higher the pressure.
Container Walls: Discuss how gas particles exert pressure on the walls of their container. Explain that when particles collide with the walls, they exert a force over a specific area, which is the definition of pressure (force per unit area).
Particle Speed and Pressure: Connect particle speed to gas pressure by explaining that when gas particles move faster, they collide with the walls more frequently and with greater force, resulting in higher pressure. Conversely, slower particle motion leads to lower pressure.
Pressure and Volume: Discuss the relationship between gas pressure and volume using Boyle's Law. Explain that according to this law, at a constant temperature, if the volume of a gas decreases, the gas particles have less space to move and collide with the walls, resulting in an increase in pressure, and vice versa.
Pressure and Temperature: Introduce Charles's Law, which states that at a constant pressure, the volume of a gas increases as the temperature increases, and the volume decreases as the temperature decreases. Explain that when gas particles gain more kinetic energy with increased temperature, they move faster, collide more frequently, and exert higher pressure.
Pressure Units: Introduce common units of pressure such as pascals (Pa) or kilopascals (kPa) and explain their relationships to other units like atmospheres (atm) or pounds per square inch (psi). Help students understand how to convert between different pressure units.
Atmospheric Pressure: Explain that the Earth's atmosphere exerts pressure on objects at the surface, known as atmospheric pressure. Discuss how variations in altitude and weather conditions can affect atmospheric pressure.
Real-World Examples: Provide relatable examples of gas pressure in everyday life, such as inflating a balloon, using a bike pump, or the pressure changes experienced during air travel. Relate these examples back to the particle model and the concepts discussed in class.
Demonstrations and Simulations: Conduct experiments or use simulations to demonstrate gas pressure, such as using a pressure gauge to measure the pressure of a gas in different situations or using a simulation to visualise gas particle motion and collisions.