Let the uncertainty sit before you reveal the experiment. Learners will naturally split between 'yes, chemicals can combine on their own' and 'no, something else must have been needed'. Both instincts are reasonable, and that's exactly the tension Miller and Urey set out to test.

Emphasise the words on the board (oceans, gases, volcanoes, lightning). It gives learners something concrete to reach for instead of guessing blindly.

Don't rush past the reveal. Knowing that two real scientists actually built this in a flask in 1953 is what turns the hook from a thought experiment into something learners want the answer to.

On Pathway 1, ask learners to explain in their own words why energy was needed to turn gases into amino acids. It's easy to remember 'lightning' as the answer without understanding what the lightning was actually doing.

On Pathway 2, get learners to test MRS GREN on something in the room, the classroom plant or their own pencil case works well. Applying the framework to something real is what makes it stick, rather than just memorising the acronym.

If a learner asks whether viruses are alive, don't resolve it for them. It's a genuinely open question in science, and that uncertainty is worth presenting honestly.

'Which fact surprised you most' is a good one to reach for with a learner who's gone quiet, it works on either pathway.

Frame this properly before pairs start: they're not deciding what's alive, they're auditing for the exact point where each item fails. That reframing is what stops the activity turning into a guessing game.

Fire and icicles are the ones that catch people out because they look like they're doing something alive, moving, growing, consuming fuel. Push learners to name exactly which MRS GREN box each item ticks and which ones it doesn't, rather than accepting a general 'sort of alive' answer.

The seed is worth spending a moment on. It looks dead but passes all seven, it's dormant, not lifeless. That's often the biggest surprise in the room.

Viruses will likely split the class, and that's fine. Let pairs disagree and defend their verdict rather than pushing for one correct answer.

The reflective question asks whether today's evidence challenged what learners assumed 'alive' means. Push for a specific piece of evidence in their answer, not just 'yes it did', that's what turns it into a real reflection rather than a one-word response.

The lock-in is short, so just read it as it is: 'Life is not a strange accident. It is simply what happens when the natural laws of physics and chemistry get to work.'