If a solid line represents a covalent bond and a dotted line represents intermolecular attraction, which of the choices shows a hydrogen bond? 1. H−H
2. H4C⋯H−F
3. H3N⋯H−O−H
4. H2O⋯H−CH3

3

Explanation:

Hydrogen bonding occurs between molecules in which hydrogen is bonded to a highly electronegative atom such as nitrogen, oxygen, chlorine, etc.

In option 3, the two compounds are H3N and H2O. In both molecules, hydrogen is directly attached to highly electro negative atoms(nitrogen and oxygen respectively). Hence, it is only in option 3 that we observe hydrogen bonding.

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.

what does the table look like