Which type of substance is made of only one kind of matter and has definite properties?

a. a molecular substance

b. an atomic substance

c. a pure substance

d. a chemical substance

a pure substance

Explanation:

A pure substance is made up of only one kind of matter and has definite properties. A pure substance has matter having an invariant chemical composition and distinct properties. A pure substance can be an element or a compound.

An element is a fundamental substance that cannot be separated into smaller substances by chemical method. A compound is a substance composed of two or more elements in fixed proportions and can be separated into smaller substances or elements by chemical methods only.

before, trains worked using the steam engine. thus, it uses heat so it is crucial to apply heat balance. the steam engine absorbs energy during the stage of boiling water. so, this is the endothermic reaction. when the steam is used to work the piston, it has to release this energy through running the train. the excess energy is released as an exhaust to the chimney. this is the exothermic process because it releases energy to the surroundings.