C7 chemistry

 - Carboxlic acids react with alcohols to form esters

-  This reaction is carried out in the presence of a stong acid catalyst

- Esters are used in the manufacture of perfumes and food products and are also found in solvents(a liquid that can dissolve another substance to produce a solution) and plasticizers (a material added to a plastic to make it more bendy)

the characteristic properties of carboxylic acids are due to the presence of the functional group - COOH

the two simplest carboxylic acids are - methonoic acid and ethonic acid

vinegar is a dilute solution of ethanoic acid

many carboxylic acids have unpleasent smells and tastes for example they are responsible for the smell of worn socks and the taste of gone of butter

the alkanes are a group of hydrocarbons. in an alkane..

• the carbon atoms are joined together by single cabon-carbon bonds
• all the carbon atoms are linked to four carbon or hydrogen attoms by a single bond

alkanes contain only single bonds so are saturated(a hydrocarbon molecule with no double bonds) hydrocarbons.

alkanes dont react with acids because the C-C and C-H bonds are strong and unreactive.

the characteristics of alcohols are due to the precence of the functional group -OH

the two simplest alcohols are methenol and ethenol

Alcohols react with sodium to produce a salt and hydrogen gas for example

• ethenol + sodium > sodium ethoxide + hydrogen

sodium sinks in alcohol, doesnt melt and steadily gives off hydrogen

in a chemical reaction, the bonds in the reactants must be broken and new bonds made to form the products

the activation energy is the energy needed to break the bonds to start the reaction

in a chemical reaction -

• making bonds is an exothermic process (they give out heat to there surroundings)
• breaking bonds ia an endothermic process (they take in heat from there surroundings)

some chemical reactions are reversible. in a reversible reaction, the products can react together to produce the origional reactants

• A + B <> C + D

This means that..

• A and B can react together to produce C and D
• C and D can react together to produce A and B

an example of this is the freezing and melting process