Assume there is 100g of the substance at first
Magnesium + Hydrocloric acid -> Magnesium chloride + hydrogen
You can observe a single displacement reaction
"Describe to show that the has formed is hydrogen"
I don't know what you mean. I can show the chemical equation though.
Mg(s) + 2 HCl(aq) --> MgCl 2(aq) + H 2(g)
One type of chemical process that can be either exothermic or endothermic is dissolving of salts in water. A salt is a compound made up of positively charged ions and negatively charged ions which are held together in a solid state because the positive and negative charges attract one another.
1st and 4th options are suitable answers, as these 2 changes are not exactly physical changes as it cant return back to original form and as well as its not cooling, so I feel its 1st and 4th options