The alkane, hexane, ${\mathrm{C}}_6{\mathrm{H}}_{14}$, can exist as five different structural isomers. An isomer is a compound that has the same molecular formula but a different structural formula. For example, butane can exist as a straight chain or as the isomer $2$-methylpropane. Both these isomers have the molecular formula ${\mathrm{C}}_4{\mathrm{H}}_{10}$. Apply your knowledge of nomenclature rules for the naming of alkanes and determine the structure and name of the five different isomers of hexane.

This graph shows the Antarctica mass variation since $2002$. 

Interpret the presented data and describe the trend over the past $16$ years.

This graph shows the Antarctica mass variation since $2002$. 

Apart from the overall trend in the data, hypothesise why there are small upward and downward variations in the total land ice mass within a calendar year.

This graph shows the Antarctica mass variation since $2002$. 

Estimate the change in mass for the period $2004–2008$.

This graph shows the Antarctica mass variation since $2002$. 

Analyse the data and comment whether the rate of loss of mass is increasing or decreasing, in the decade following $2008$. Support your argument with mathematical evidence.