KS4 students have been studying the differences between endothermic and exothermic reactions. Also the meaning of reversible reaction and the rate of reaction.
Sodium acetate or hot ice is an amazing chemical reaction that can be prepared with baking soda and vinegar. It can cool to a sodium acetate solution below its melting point and then cause the liquid to crystallise.
Crystallisation is an exothermic process, so the resulting ice is hot. The solidification occurs so fast that it can form sculptures while pouring hot ice.
Here is the reaction between the baking soda and vinegar to produce the sodium acetate:
Na+[HCO3]– + CH3–COOH → CH3–COO– Na+ + H2O + CO2