(a) What is a monomer? (b) Which of these molecules can be used as a monomer: ethanol, ethene (also called ethylene), methane?

A monomer is a small molecule that can chemically bond with other monomers to form a larger, more complex structure called a polymer. Monomers possess the ability to form covalent bonds with other molecules, allowing them to combine and create a polymer chain. Examples of monomers include glucose, amino acids, and nucleotides.

Let's analyze each of the given molecules: 1. Ethanol: Its chemical formula is C2H5OH. Ethanol is a simple alcohol and does not possess the ability to form long chains or polymers. Therefore, it cannot be used as a monomer. 2. Ethene (Ethylene): Its chemical formula is C2H4. Ethene is an unsaturated hydrocarbon with a double bond between the two carbon atoms. The double bond can be broken to form a single bond and create a new bond with another ethene molecule. This process is known as polymerization, and ethene can be used as a monomer to form polyethylene. Hence, ethene (ethylene) can be used as a monomer. 3. Methane: Its chemical formula is CH4. Methane is a saturated hydrocarbon with no double or triple bonds, meaning it cannot easily form into long chains or polymers. As a result, it cannot be used as a monomer.

Out of the given molecules - ethanol, ethene (ethylene), and methane - only ethene (ethylene) can be used as a monomer.