What is the compound having $(-CHO)$ functional group called?

Complete the following chemical reactions and write the chemical name of the products obtained.
$(i)$ $CH_{2}=CH_{2} + H_{2}O \longrightarrow$
$(ii)$ $CH_{3}COOH + NaOH \longrightarrow$
$(iii)$ $CH_{3}CH_{2}OH \xrightarrow{H_{2}SO_{4}} $
$(iv)$ $HCOOH + Na \longrightarrow$
$(v)$ $C_{2}H_{5}OH \xrightarrow{\text{Alk. } KMnO_{4}} $

List two characteristic features of carbon which,when put together,give rise to a large number of carbon compounds.

$CH_3-CH_2-OH \xrightarrow{\text{Alkaline } KMnO_4 + \text{Heat}} CH_3-COOH$
In the above given reaction,alkaline $KMnO_4$ acts as:

"Saturated hydrocarbons burn with a blue flame while unsaturated hydrocarbons burn with a sooty flame". Why?

Which of the following polymer substances is inert towards environmental processes?