The diagram shows the structure of a propene molecule - Edexcel - GCSE Chemistry - Question 3 - 2011 - Paper 1

To illustrate the polymer structure, draw a line or chain connecting the two propene molecules. Each propene molecule should be represented showing the carbon-carbon bond formation, where the double bond between two carbon atoms in the propene units transforms into a single bond in the polymer.

To test for the presence of carbon-carbon double bonds in propene, you can use bromine water. When bromine water is added to propene, the solution will decolorize, indicating that a reaction has occurred and confirming the presence of double bonds.

To find the total mass of products formed, apply the principle of the conservation of mass. Since no atoms are lost during the reaction, the total mass of the products will be equal to the mass of the reactants, which is 17 g.

Cracking is a chemical process in which larger hydrocarbon molecules are broken down into smaller, more useful molecules, such as alkenes and alkanes. This process is often facilitated by heat and sometimes a catalyst.

Cracking is necessary because larger molecules typically have low demand and are less useful as fuel. Additionally, smaller molecules, such as alkenes, are valuable in the production of fuels and polymers, making cracking a crucial step in maximizing the utility of crude oil.