Which of the following compounds has a sweet,fruity smell?

Write the name of the next homologue of $CH_{3}OH$ and $HCOOH$.

Draw the structure of the simplest ketone.

What is meant by homologous series of carbon compounds? Classify the following carbon compounds into two homologous series and name them.
$C_{3}H_{4}, C_{3}H_{6}, C_{4}H_{6}, C_{4}H_{8}, C_{5}H_{8}, C_{5}H_{10}$

$(a)$ Differentiate between soap and detergent.
$(b)$ Explain why soaps form scum with hard water,whereas detergents do not.