4.Identify each substance in the following word equation as a reactant or a product limestone heat lime + carbon dioxide

5.What is the difference between an exothermic and endothermic reaction?

Explanation:

4.                 limestone heat lime + carbon dioxide

The reactants in this expression above is limestone

The products of the reaction is carbon dioxide and lime

Reactant is the species that gives the product and it is usually found on the left hand side of the expression.

The product is the substance on the right hand side of the expression that forms through the experiment.

Heat is used to facilitate the reaction.

5. An exothermic reaction is a reaction in which heat is given off.

An endothermic reaction is a reaction in which heat is absorbed in the process.

An exothermic reaction is always warmer after the reaction whereas an endothermic reaction is colder at the end of the reaction.

1 is the answer to this problem

nuclear fission produces elements that are heavier than helium.

the elements that are used in nuclear fission and their products are much heavier than helium.