what approach do you suggest using to prevent your water sample from cooling off beore you start your measurements?

3 answers

I don't know enough about your experiment to answer. Are you using a bomb calorimeter of constant volume? A syrofoam cup calorimeter?
I'm using nested styrofoam coffee cups
Knowing as little as I do about the experiment, have what you need pre-measured, pre-weighted, equipment ready to go, and make the addition of the hot water to last thing you do before starting mesurments.