Combine the given two facts to write a concluding fact. Note that there should be some parts of the first and second facts that are not mentioned in this conclusion fact. Your combined fact should be the result of a chain between the two facts. Chains form when two facts connect together to produce a concluding fact. An example of a chain is: "pesticides cause pollution" (fact1) + "pollution can harm animals" (fact2) → "pesticides can harm animals" (conclusion fact). Parts of the concluding fact overlap with the first and the second fact. To construct such a  concluding fact, a useful way is to borrow the subject from one fact and the ending conclusions from another fact.

Fact 1: the volume of an object can be used to describe the size of that object. 
Fact 2: Size is a relative aggregate measure of volume and mass.
The volume of an object can be used to measure the mass of the object.

Fact 1: Blood pH may become unbalanced if the rate of breathing is too fast or too slow. 
Fact 2: Acidity is measured with a pH meter or with pH paper strips.
Blood acidity may become unbalanced if the rate of breathing is too fast or too slow.

Fact 1: Smog contains particulates. 
Fact 2: Fine particulates are tiny pieces of soot and dust that lodge deeply in the lungs.

smog contains tiny pieces of soot and dust.