Question

A student says that all pure substances are elements. Do you agree? Why or why not?

Question 14 options:

I disagree.  Elements form all pure substances, but some pure substances include elements bonded together to form molecules and compounds. I disagree.  All pure substances are also mixtures. I disagree.  Elements are not pure substances.  All pure substances include only molecules and compounds, which are more complex. I agree.  Pure substances include only single atoms made of one element.

Answer 1

The answer is I disagree. Elements form all pure substances, but some pure substances include elements bonded together to form molecules and compounds.

Step-by-step explanation:

In chemistry a pure substance is either an element or a compound. Therefore hydrogen, oxygen, sodium, iron, copper etc all are pure substances; and same is the case with compounds such as water, sugar, ammonia, sodium chloride, methane, ethanol etc. A compound is composed of two or more elements combined in a fixed ratio by mass so we can say that some pure substances include elements bonded together to form molecules and compounds.

Answer 2

Answer: I disagree. Elements form all pure substances, but some pure substances include elements bonded together to form molecules and compounds.

Step-by-step explanation:

Pure substances are those that have a uniform and constant (invariable) composition.

That condition is met by both elements and compounds.

Elements are pure substances of one only kind of atoms. For example, gold, oxygen, sodium, hydrogen, are pure substances that arer elements. There are 118 elements known and they are all listed in the periodic table.

Compounds are pure substances formed by two or more different kind of atoms. Water (H₂O), table salt (NaCl), and ethanol (CH₃-CH₂OH), are examples of pure substances that are compounds. There are pratically infinite different compounds.

In conclusion, compounds are also pure substances, since every sample of a given compound has always the same kind of elements bonded in the same way.