Which is not a compound?

sugar
water
silicon dioxide
gold

gold

Explanation:

Element is a pure substance which is composed of atoms of similar elements. Example: Argon with atomic symbol

Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.

Example: Water with formula and contains hydrogen and oxygen in a fixed ratio by mass

1. Sugar has chemical formula of [texC_{12}H_{22}O_{11}[/tex] and thus is a compound.

2. Water has chemical formula of and thus is a compound.

3. Silicon dioxide has chemical formula of and thus is a compound.

4. Gold has chemical formula of and thus is an element.

you gotta add the following molecules so we can give u an answer

explanation:

hydrocarbons are organic compounds that contain only hydrogens and carbons. they can be saturated (those which contain only carbon-carbon single bonds) or unsaturated (those which contain carbon-carbon double or triple bonds) in nature. hydrocarbons can undergo several reactions like substitution, elimination etc.  

on substituting one or more hydrogen atoms in hydrocarbon it results in the formation of haloalkane. as the halogen atoms are large compared to the carbon and hydrogen atoms, due to which the molecular weight increases and the bond become polar because of presence electronegative halogen atom and results in the increase in boiling point of the haloalkane.

thus, the correct option is (b) that is the boiling point of the new compound increases on substituting a hydrogen atom with a halogen in a hydrocarbon.