Answer
a. mixture, homogeneous;
b. pure substance, compound;
c. pure substance, element;
d. mixture, heterogeneous
Work Step by Step
A pure substance is composed of only one single type of atom or molecule. An element can't be broken down into smaller, simpler units. A compound is composed of two or more elements.
A mixture is composed of two or more different types of atoms or molecules that can be combined in variable proportions. In a homogenous mixture, the atoms or molecules are mixed uniformly. In a heterogeneous mixture, the atoms or molecules are mixed randomly.
