The structure of one molecule of a compound is shown in Figure 10 - Edexcel - GCSE Chemistry - Question 7 - 2022 - Paper 1

The compound in Figure 10 is described as an unsaturated hydrocarbon because it contains at least one double bond between carbon atoms. Unsaturated hydrocarbons can react with hydrogen in a process called hydrogenation, which can convert them into saturated hydrocarbons.

Substance Y, formed from many molecules of the compound in Figure 10, is a polymer. Polymers are large molecules made up of repeating structural units, which, in this case, are derived from the alkane compound.

To calculate the mass of one molecule of substance Y, we use the mass of one molecule of the compound from Figure 10, which is 6.98 x 10⁻³ g. Then, we multiply by the number of molecules:

Mass of one molecule of Y = 6.98 imes 10^{-3} ext{ g} imes 64800 ext{ molecules} = 452.784 ext{ g}

Thus, the mass of one molecule of Y is 452.784 g.

Complete combustion of alkanes occurs when there is a sufficient supply of oxygen, resulting in the formation of carbon dioxide and water, and produces maximum energy. The general word equation for complete combustion of an alkane (like methane) is:

Alkane + Oxygen → Carbon Dioxide + Water

Incomplete combustion occurs when oxygen supply is limited, leading to the production of carbon monoxide (a toxic gas) and/or carbon (soot), resulting in lower energy yield. The general equation for incomplete combustion is:

Alkane + Insufficient Oxygen → Carbon Monoxide + Water

The trend shown in the temperature change of water when different alkanes are burned indicates that as the carbon chain length increases, the energy released during combustion also increases, leading to a higher temperature change. This trend is attributed to the increased number of C-H bonds present in longer-chain alkanes, which release more energy when they are broken during combustion.