True or false easy 15 points pure substances are made up of single elements or compounds. true false

The given statement is true.

Explanation:

A pure substance is defined as the substance which is formed by same or different type of atoms which are chemically combined in a fixed ratio by mass.

Compounds and elements are considered as pure substances.

For Example:  Sodium and sodium chloride are both considered as pure substances because sodium is entirely made up of sodium atoms and sodium chloride is entirely made up of sodium chloride molecules.

Hence, the given statement is true.

c is the answer because when something is left after something evaporates that shows the chemical change.

the potential energy of the reactants is 200j.

from the energy diagram, the energy of the product formed is 350j; this means that, this reaction is an endothermic reaction, because it absorbs energy from its environment.