1. CHEMICAL KINETICS
Study of rates of chemical reactions, factors which affect these rates, and the reaction mechanisms by which these reactions occur

2. Reaction rates vary – some are very fast…
… while others are quite slow.
NOTHING LASTS FOREVER.

3. FACTORS THAT AFFECT REACTION RATES
1. NATURE OF REACTANTS
Some materials like paper, wood and gasoline burn easily
Some metals easily replace other elements from their compounds
2 Na + 2 H2O  2 NaOH + H2
Au + H2O  no reaction
Reason : Activity series of metals

5. 2. CONCENTRATION OF REACTANTS
An increase in the concentration of the reactant increases the reaction rate
Air is 21% O2 and 78% N2. Why?
N2 is unreactive while O2 is more reactive (combines with other elements). Therefore N2 has a chance to accumulate in the atmosphere.
If our atmosphere is pure O2, then there would be no slow burning but an explosion (fast burning). This is what happened in January , when three astronauts – Virgil Grissom, Edward White and Roger Chafee, died in a flash fire that swept their oxygen filled space capsule.

7. 3. SURFACE AREA OF THE REACTANTS
When you start a fire, you usually use smaller pieces.
Steel wool burns in fire, solid steel does not.
This is also the reason why foods need to be chewed thoroughly before ingesting. Chewing reduces the size of the food and makes it more digestible.

9. 4. TEMPERATURE
Reactions occur faster at higher temperatures.
Food spoilage is retarded by refrigeration.

10. 5. PRESENCE OF CATALYST AND INHIBITORS
CATALYST – substance that speeds up the rate of reaction without being used up.
INHIBITORS – substance that slows down the rate of reaction.

11. Hydrogen peroxide is stored in dark bottles to prevent its exposure to light.
2 H2O2  2 H2O + O2

12. Browning of peeled potatoes can be prevented by pouring Vitamin C or ascorbic acid present in citrus fruits. The ascorbic acid is oxidized first, thus preventing the browning of the potato.
Anti-oxidants such as sodium bisulfate, propyl gallate or butylated hydroxyl toluene (BHT) are used as food preservatives.