Welcome to the fifth instalment of the ‘Making it Relevant’ series.
Firstly, we are going to take a look at why we teach Particles and Matter at GCSE. Then the content typically required in the new GCSE specifications will be summarised. Finally we will be thinking about how this can be made engaging and relevant to all our students. Planning a new scheme of work should involve looking at the big ideas you want to present, and then how to tailor them to your particular students.
The chair you are perched on, the computer you are using, the coffee you are drinking. These things are all made of particles. Tiny particles behaving differently in different conditions. This topic is one to set our students thinking about how we can change the nature of substances, and how the nature of the world around us is shaped by particles.
There are three main topics in the specification:
Changes of State
How changing the state affects the density of a substance. The correct terms for changing states.
The potential effects of changing the temperature on the energy contained within a substance. How to describe changes in energy on a graph and identify changing states of matter.
How temperature, pressure and volume affect the characteristics of a gas. How doing work on a gas changes it.
As misconceptions go, the one about mass changing as things melt or vaporise is a stubborn one. This topic will go more smoothly if you ensure your students all understand the concept of conservation of mass before you proceed too far. A simple observation of mass as ice is melting (especially if it is winter and there is actually snow that can be used!) or as a fizzy vitamin tablet dissolves (trapping the gas in a balloon above your flask) can provide the proof that some students need to see.
Modelling internal energy can be done by having students in groups moving as the particles would in each state of matter, and changing their motion as energy is added to or leaves the system. Alternatively, pictorial representations can make beautiful classroom display resources.
When it comes to gases, it can be difficult for some students to understand that they are actually made of particles, because they can’t be seen. May be they could pump up a tyre or a balloon. Ask them to observe the temperature change in the pump. Can they explain why the balloon is now inflated? What happens when the valve of the tyre is released, what does the gas feel like as it rushes out? Why do they think a bottle collapses when all the gas is removed?
For a homework you could try asking your students to find examples of changes of state occurring in their dinner preparations, and to draw the particle representations. Can they try working out how much energy it take to heat up the pan of water thy are boiling their peas in, or calculating the energy needed to melt all the cheese on their pizza?
Required Practical Investigations
Finding the density of regular and irregular solids and of liquids is a required practical best suited to teaching in this topic. The practical elements are fun (if a little soggy) and lend themselves nicely to discussions on the repeatability of the experiment. For instance why are the methods for establishing the density of liquids and regular solids more reproducible than for irregular solids? One look at the puddles on your floor might help answer this!
There is another required practical about calculating the specific heat capacity of a metal block. This can also be covered in the energy topic though. Conceptually this can be a challenge for students. There are a number of calculations to be made regarding the work done by the heater. If the electricity topic has not been taught by this point then students can be left wondering the exact purpose of the calculations. This can be distracting from the actual purpose of the investigation. Also it is worth checking with your maths department about gradients. How (and when) are they taught? It can be frustrating for students (and teachers!) to do a practical but have the purpose of it overshadowed by the high maths demand of the analysis.
This is one of the topics with many opportunities for your students to do some hands on investigating, make the most of it!