Australia's Science Forum

As Ammonium Nitrate is a No No these days,

A replacement for Hot/Cold Experiment

Citric acid solution: 2-3 spoonfuls of Citric acid in 200ml of water. Take 25ml of the above Citric acid Solution and mix with 15g Sodium Bicarbonate in a zip lock bag. Creates a cold reaction as Ammonium Nitrate when squeezed in your hand.

If you don't need analytic results less measuring one you and just put 1-3 teaspoons of solid Bi-carb and solid Citric Acid in the zip lock bag and add enough water to get it wet and mix it by squeezing. Also makes a good emergency ice pack for sports injuries. Be cafeful that the zip lock bag isn't closed as there is gas formed and needs to escape. We did it in a 50mL Beaker.

Also Potassium Iodide in Water is Endothermic enough to have a measurable temperature difference and cause condensation on the beaker.

What do you use or the copper ion prac? We clip copper strips on opposite sides of a petri dish hooked up to 6volts, in a solution of NH4NO3 and conc NH4. This produces blue copper ions. Then swap the + and - . So long as it's only 6 volts it doesn't smell too bad. Use extraction fans etc. Collect waste for disposal.

This thread has an Endothermic prac.