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Skip to 0 minutes and 8 seconds Practical work can be used as an effective assessment tool. Here we are doing a simple experiment, which can be set as an enquiry activity. What is the power of a candle? We give students a range of simple equipment, to try and measure the power output of a candle. Before students do this, they need to have done other experiments and an understanding of some particular areas of science. They may have done some specific heat capacity questions and also used thermal power equations. Students might need some prompting, and so cards can be used with different amounts of information, such as specific heat capacity of water, or the equations they may need.

Skip to 0 minutes and 48 seconds Once they are going, the teacher does not have to intervene much. Students can try and work their way through the activity as unaided as possible and the teacher can listen and observe, which allows a good chance to see how well students are understanding. Students have to use two equations, as well as make conversions between units, to be able to come out with an answer. What is the right answer? Well, it varied. An internet search for the power output of a candle will come up with a wide variety of answers. Which is very good, as if students ask “what’s the right answer?”, the teacher can just say “I don’t know. You tell me.”

Skip to 1 minute and 26 seconds Students often assume there is always a correct answer, and that eventually teachers will give them the right answer. Here that won’t happen. Getting students to compare their answers as a class is very useful and they will find it’s around 4 to 15W possibly. Teachers can also probe students understanding of the practical and how it might be improved. For example, why results vary so much and students will be able to make effective suggestions. This is a poor practical for getting “the right answer” for so many reasons that students will pull out. However, for assessing students’ capabilities for thinking through a practical and demonstrating understanding of the equations is the true focus of this practical.

Practical work as an assessment tool

Looking further now at varied assessment activities, and in particular the advantages of teaching science as a practical subject, practical work has a key role in formative assessment. Practical activities can be very useful for students to demonstrate their learning, especially if the activity is set in a different context to the examples they might have been taught.

If a practical activity is well thought through, it requires minimal intervention from the teacher, which enables the teacher to move around the classroom watching, listening and asking questions of students. This can give rich evidence on how well the students understand a topic.

In this video we look at one example to assess students’ understanding and application of a body of knowledge from the physics curriculum, energy transfer and specific heat capacity, set in the novel context of working out the power of a candle.

This practical also gives an opportunity to see how well students can apply mathematical skills, often an area that students struggle with in science, and we consider this in more detail in the next section of this week.


The kind of practical activity shown in the video provides a low-stakes method of assessment, and avoids the anxiety which often accompanies written tests.

Have a look at one section of your current scheme of learning, and identify ONE practical which could be used in a similar way. How would you structure the activity so that there is a focus on assessing student’s understanding?

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Curriculum Design for Secondary School Science

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