Lesson 3: Particle behaviour

Summary: / Students work in pairs to carry out simple investigations illustrating expansion, diffusion, pressure changes and changes of state.
Coverage: / NC 2014 KS3: The particulate nature of matter: the properties of the different states of matter (solid, liquid and gas) in terms of the particle model, including gas pressure.
Lesson objectives: / To explain expansion using Particle Theory; to make careful observations
Lesson outcomes: / Students observe and measure phenomena and write explanations using Particle Theory.
Working Scientifically outcomes: / Select, plan and carry out the most appropriate types of scientific enquiries to test predictions; Interpret observations and data, including identifying patterns and using observations, measurements and data to draw conclusions.

Progress criteria

Learning / Mastering / Expanding
Students can:
  • recall that materials expand when heated
  • describe their observations when carrying out the investigations.
/ Students can:
  • use the particle model to explain expansion and contraction.
/ Students can:
  • explain all their observations using Particle Theory
  • make suitable measurements.

Skills opportunities

Literacy / Maths and data handling / STEM
Reading: (Main) Students read to extract information for writing, then read and follow written instructions.
Writing: (Main) Students write a scientific explanation. / Students measure temperature, time and volume. / Students think about how engineers work with expansion and contraction.
Resources
Student’s Book: / Unit 2: page 123 (What are expansion and contraction? How do we measure expansion and contraction?)
Answers to Student’s Book questions: / Unit 2: C2.1
Practicals and Investigations: / Room for expansion
Structured Questions: / Particle behaviour, question 1

Preparation for lesson

You will need the ball and ring equipment for the starter activity and the equipment for the Practicals and Investigations ‘Room for expansion’.

Starter(5 mins)

Demonstrate the ball and ring experiment. Show the students that the ball will fit through the ring. Now, heat the ball strongly in a blue Bunsen flame. As you do this, remind students about the particle model and how particles are arranged in a solid and that they vibrate. As a solid is heated the particle will gain more energy and move more. Ask them to predict what they think will happen as the ball is heated, using Particle Theory. Show them that the ball no longer fits.

Main(45–50 mins)

Ask the students to write a scientific explanation for the starter demonstration. They can use the information on page 123 of the Student's Book for support. They should explain what happened using particles and include a diagram in their explanation. Ask them what they think will happen now that the ball has cooled down. Show them that the ball now fits, and question the class as to why. Explain that materials expand when they are heated because the particles' movement increases and they get slightly further apart. Liquids and gases also expand. Materials contract when they cool.

Tell the students that they are going to carry out some of their own investigations and explain what is happening, using Particle Theory. Ask the students to work in pairs and follow the instructions on the Practicals and Investigationssheet ‘Room for expansion’. They carry out simple investigations illustrating expansion, diffusion, pressure changes and changes of state. Students plan, measure and write a conclusion for each investigation.

Plenary (5 mins)

Assign each group one of the experiments from the Practicals and Investigations sheet ‘Room for expansion’ and ask them to explain what they observed using Particle Theory. At this stage, it is not essential that their ideas are correct as long as they can justify them (as each phenomenon will be covered again in later lessons). Go through their ideas, making sure to correct any misconceptions
at this stage.

Tackling common misconceptions

Ensure that students understand that the size of the particles is fixed. The motion can change depending on the temperature; an increase in temperature increases the kinetic energy of the particles and they vibrate faster, but the particles themselves do not get bigger. However, the material will expand as the particles spread out.

Differentiation

Support / Extend
Ask pairs to just carry out one of the investigations and pool the results as
a class. / Students should take measurements during the practical tasks in order to collect data to back up their observations.
Present some more examples of expansion and contraction to the students and ask them to discuss in pairs what is happening in terms of the particles. Suitable examples: explain how a thermometer works, explain why there are gaps left between two lengths of railway track laid end-to-end and why in the past metal 'tyres' were heated before putting them onto wooden wheels.

Homework or Extension activities

Learning / Mastering / Expanding
Students complete Structured Questions ‘Particle behaviour’, question 1a–b. / Students complete Structured Questions ‘Particle behaviour’, question 1c–d. / Students complete Structured Questions ‘Particle behaviour’, question 1e. Ask students to do some research and write down more examples of where engineers use expansion and contraction.

How to move your students on…

Learning / Mastering / Expanding
Students discuss that most substances can exist in all three states of matter. / Students discuss what melting and boiling points are. / Students discuss how the rate of diffusion in liquids can be increased.