LDPE is formed by heating ethene at 200° to 300°C under oxygen as a catalyst. The reaction follows free radical mechanism. The peroxides formed from oxygen acts as a free radical initiator.

(i) Antioxidants are substances which retard the oxidative deteriorations of food.
(ii) Food containing fats and oils is easily oxidised and turn rancid.
(iii) To prevent the oxidation of the fats and oils, chemical BHT(butylhydroxy toluene), BHA(Butylated hydroxy anisole) are added as food additives.
(iv) They are generally called antioxidants. These materials readily undergo oxidation by reacting with free radicals generated by the oxidation of oils, thereby stop the chain reaction of oxidation of food.

(i) Aroma compounds
(ii) Food colours
(iii) Preservatives
(iv) Stabilizers
(v) Artificial Sweeteners
(vi) Antioxidants
(vii) Buffering substances
(viii) Vitamins and minerals

(i) Natural rubber is mixed with 3-5% sulphur and heated at 100-150°C causes cross-linking of the cis-1,4-polyisoprene chains through disulphide (-S-S-) bonds.
(ii) The physical properties of rubber can be altered by controlling the amount of sulphur that is used for vulcanization.
(iii) In sulphur rubber, made with about 1 to 3% sulphur is soft and stretchy.When 3 to 10% sulphur is used the resultant rubber is somewhat harder but flexible.

(i) Preservatives are chemicals added to food which are capable of inhibiting, retarding or arresting the process of fermentation, acidification or other decomposition of food by the growth of micro organisms (or)
(ii) Chemical substances which are added to food that prevents the spoilage of food materials by destroying the food - spoiling micro-organisms are called food preservatives.
(iii) Eg: sodium benzoate, NaCl, Acetic acid Sodium metabisulphite, potassium meta bisulphite etc.

Detergents:
a) Anionic detergents:
These are sodium salt of sulphonated long chain alcohols (or) hydrocarbons. The anionic part of the molecule is involved in the cleansing action.
Eg: sodium lawryl sulphate, sodium dodecyl benzene sulphonate.
Use: Household work & tooth paste.
b) Cationie detergents:
These are quarternary. ammonium salts of amines with acetates, chlorides (or) bromides as anions. 
It is the cationic part of the molecule which is involved in cleansing action.
Eg: n-hexadecyl trimethyl ammonium chloride
c) Non-ionic detergents:
These donot contain any ion. These are esters of high molecular mass alcohols.
Eg: Pentaerythrityl stearate
Use dish washing detergents.

Detergent Type	Example
Anionic detergent	Sodium Lauryl Sulphate (SLS)
Cationic detergent	N - hexadecyltrimethyl ammonium chloride N,N,N - trimethylhexadecan - 1 - aminium chloride
Non - ionic detergent	Pentaerythrityl stearate 3 - hydroxy -2,2 - bis (hydroxymethyl) propyl heptanoate

The drug molecule interacts with biomolecules such as enzymes, receptors etc., which are referred as drug targets.

Proteins.

(i) When a drug molecule that has a similar geometry (shape) as the substrate is administered, it binds to the enzyme and inhibits its activity.
(ii) In other words, the drug acts as an inhibitor to the enzyme catalyst. These type of inhibitors are often called competitive inhibitors.

Aspirin is o-acetyl salicylic acid

(i) They are neurologically active drugs. 
(ii) It acts on the central nervous system by blocking the neurotransmitter dopamine in the brain.
Uses : Reducing stress & anxiety, To cure sleep disorders & severe mental disease.
Ex : (i) Major tranquilizers : Haloperidol, Clozapine
(ii) Minor tranquilizers :Diozepam(Valium), alprazolam.

(i) Many drugs exert their physiological effects by binding to a specific molecule called a receptor whose role is to trigger a response in a cell.
(ii) The chemical messengers, bind to the active site of these receptors. This brings about the transfer of message into the cell.
(iii) The chemical messengers bind to the active site of these receptors.
(iv) This brings about the transfer of message into the cell
(v) These receptors show high selectivity.
(vi) If we want to block a message, a drug that binds to the receptor site should inhibit its natural function.
(vii) Such drugs are called antagonists.
(viii) In contrast, there are drugs which mimic the natural messenger by switching on the receptor. These type of drugs are called agonists.

(i) Thermoplastic: They become soft on heating and hard on cooling. They can be remolded
E.g. polythene, PVC, polystrene
(ii) Thermo setting : Do not be come soft on heating set to an infusible mass upon heating.
E.g. bakelite, melamine, formaldehyde

1. The materials that are readily decomposed by microorganisms in the environment are called biodegradable.
2. Natural polymers degrade on their own after certain period of time but the synthetic polymers do not.
3. It leads to serious environmental pollution. One of the solution to this problem is to produce biodegradable polymers which can be broken down by soil micro organism.
Examples:
(i) Polyhydroxy butyrate (PHB)
(ii) Polyhydroxy butyrate-co-A- hydroxyl valerate (PHBV)
(iii) Polyglycolic acid (PGA), Polylactic acid (PLA)
(iv) Poly ( E caprolactone) (PCL)
(v) Biodegradable polymers are used in medical field such as surgical sutures, plasma substitute etc...
4. these polymers are decomposed by enzyme action and are either metabolized or excreted from the body.