Which of the following observations would indicate that a material is a pure substance?

a. it does not dissolve in water.

b. it changes color after heating.

c. it cannot be physically broken down into different types of atoms.

d. it can be physically broken down into different types of molecules.

The answer to the question is the option C. it cannot be physically broken down into different types of atoms. This means that the material is an element, which is a pure substance. Because an element is a pure substance that is formed by one only type of atoms. For example, gold is an element and all its atoms are of the same type. That is also true for any of the 118 elements of the periodic table. Compounds (other kind of pure substances) can be broken down into molecules (which contain different kind of atoms, but always in the same proportion) and mixtures (non pure substances) have different kind of substances.

zfoods? ok, pressure is used to keep the heat inside and to keep the food perfect.