Step-by-step explanation:
so why some metals react with cold water and not hot water because in the reactivity series the some of which are more reactive like potassium and sodium which can react with cold water and which react with hot water it's because those need more activation energy compared to the others so in cold water will provide less activation energy compared to hot water has thermal energy that's what I can say is that's why some metals react with hot water and cold water hot water has more activation energy, activation energy is the energy needed to initiate a chemical reaction and the diagram I would say you could use the apparatus like measuring cylinder Beaker and water so you take magnesium ribbon you first insert it in cold water will see there's no reaction but when you insert in hot water they will be formation of magnesium hydroxide and hydrogen gas.