Take a walk on the slow side

It’s no secret that running a practical is hard: chaotic scenes of students struggling with unfamiliar equipment and arcane instructions, the nagging feeling the students aren’t really learning anything.

Recently, I have been running what I call a ‘slow practical’. This is a radical departure from the ‘traditional’ route, because it doesn’t involve a method sheet or students working through the practical at their own pace. Instead, I gather students around a ‘demo desk’. Here I introduce the students to the practical and explain what we are doing and why. I then demonstrate the first step of the practical: a small, easily manageable chunk. Then students go and perform just that step and return to the demo desk. This cycle is repeated for every step in the practical – me, then you, me, then you and so on.

With slow practicals, students are calm and ordered. I can see what everyone is doing without having to move around the classroom. I can anticipate common errors and prevent students from making them. I ask students questions about what they are doing so that they understand the actual science being implemented. Weirdly, slow practicals take less time. Students manage to get the experiment done more quickly because inefficiencies like mistakes, queues, off-task behaviour and error requiring restart are pretty much eliminated. Slow practicals have improved my delivery of practicals more than anything else.

For example, let’s take a rates of reaction practical involving marble chips, acid and gas syringes. Here are the steps I would take to run this practical.

1. Before starting, ensure the students have a strong knowledge of rates of reaction.
2. Gather students at the demo table with your fully set-up apparatus.
3. Show students the marble chips of different sizes and question them on the relationship of size to surface area.
4. Add some hydrochloric acid to a beaker, and tell students you will drop some marble chips in. On a whiteboard, write ‘calcium carbonate + hydrochloric acid →’ and discuss the products of the reaction.
5. Add the products to the whiteboard and discuss the states of every substance in the equation. Ask if gas is produced, and what we will see.
6. Add the chips to the acid and see the gas evolved. Discuss how we can collect and measure the volume of that gas.
7. Talk about the different-sized chips. Explain that by noticing which chips evolve gas quickest we can establish a relationship between size of chip and rate of reaction.
8. Your students should already know who their work partner is. I generally name them A and B. I ask all the As to collect two sets of safety goggles, one for them and one for their partner. Meanwhile I ask the Bs to collect a clamp stand and gas syringe. At their desks, students will put on their specs, leave the syringe and then come back to the demo desk. I always repeat instructions once then ask a student to say them back to me.
9. Next I show students how to set up their gas syringe on a clamp stand. They go and do this, then come back.
10. I do not need to move from the demo desk. I can easily look out across the whole class and see what everyone is up to, calling out errors if needed.
11. When the students return, I have a quick look round the room to check that equipment is set up properly.
12. Repeat the above cycle for students to fetch and set up flasks, marble chips and acid.
13. When students are ready to measure out their acid, discuss why it is important to know the exact volume used and why it is important to control. Show them how to use a measuring cylinder and why they are using a particular size. Send them back to measure out the acid and pour it into the flask.
14. Next, do the same for measuring the mass of marble. Be clear about the importance of removing the weighing boat from the balance in-between additions and why. Discuss as above the need for a controlled mass of marble and so on.

As the practical progresses keep following this routine. Your students will complete a complex practical in a timely and safe manner, with no spills, chaos or loss of learning. You will come away empowered and energised because you managed to achieve a practical with ease.

So next time, make it a slow practical. You won’t believe the difference it makes.