Are you actually checking for understanding?

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Miss A taught a short section of a lesson on the greenhouse effect. They drew a nice, clear diagram and talked about how the greenhouse effect is vital for keeping the Earth at a habitable temperature, how some of the energy from the Sun is reflected by the atmosphere, that short-wave radiation is transmitted by the atmosphere and absorbed by the surface which then emits longwave radiation which is absorbed by the greenhouse gases in the atmosphere, increasing their temperature etc etc etc. Then they asked students to get their mini whiteboards out for a check for understanding (CFU). This isn't the sort of explanation that lends itself well to a QDC&C - you can erase bits of the diagram and get students to name what's missing, but the value is low - students don't need to remember the bits of the diagram; they need to remember the science [You could ask e.g. "what is happening at A?" rather than "what is A?" but it can get a bit "guess what's in the teacher's head", depending on the diagram]. From the AQA spec, this is what they need: 

https://filestore.aqa.org.uk/resources/chemistry/specifications/AQA-8462-SP-2016.PDF
Accessed: 3/3/22 18:46

So, really, it's gonna have to be questions.

Miss A asked the following: 

  • Name three greenhouse gases
  • What would be Earth's average temperature without any carbon dioxide in the atmosphere?
  • What is the greenhouse effect?
  • How do greenhouse gases keep Earth habitable?
  • Why are fossil fuels damaging to the environment?

Now, I would argue these questions are alright. They aren't bad questions. I'd even argue they're fairly good consolidation questions. They just aren't very good for checking students have understood what it is you wanted them to understand.

What do I want the students to understand from the above explanation?

  • Why are greenhouse gases important?
  • What happens to short wave radiation in Earth's atmosphere?
  • What happens to long wave radiation in Earth's atmosphere?
  • What happens to the short wave radiation that has been transmitted?
  • What happens when the surface of Earth begins to cool?
  • What happens to the molecules of the greenhouse gases in the atmosphere when they absorb this long wave radiation?
    • What effect does this have on the average temperature of Earth?
These are the things I need a student to have gotten from my explanation. Sorry, these are the things Miss A needs a student to have gotten from their explanation 😉 

To be able to answer the first set of questions, yes, you do need to understand what you've just learned, but if a student gets the question wrong, it doesn't give me as much data as the second set. If a student can't tell me how greenhouse gases keep Earth habitable, is that because they don't know what a greenhouse gas is? Or because they don't know what habitable means? Or because they haven't made the connection between the greenhouse gases and the greenhouse effect [never underestimate a student's ability to miss a seemingly obvious connection] Is it because they can't remember what the greenhouse effect is? Or maybe it's just that they don't know what I'm looking for - a full explanation of how the greenhouse effect keeps us toasty warm would be a reasonable answer, but so would something with a lot less detail. But that doesn't tell me what a student knows.

The first set of questions almost certainly has a place - for consolidation, or for independent practice, or, in the case of the "name three greenhouse gases" possibly for a prerequisite knowledge check [it could be argued you don't need to know which gases are greenhouse gases to be able to understand the greenhouse effect] But not for my CFU. For my CFU, I need instant data. I need to know with one glance exactly what bit is missing in a student's understanding. I can't be making assumptions about what a student does or doesn't know at this point. 

TL;DR
CFU answers should give you instant data about the piece of understand that may or may not be missing.