Solidification

       In solidification reaction substances changes from a liquid to a solid when its temperature is lowered below its freezing point. It is also known as freezing.
Example:
  Water changing to ice.

Saponification

               Animal fats and vegetable oils are esters of carboxylic acids. These fats and oils are called triglycerides. Triglycerides reacted with sodium or potassium hydroxide to produce fatty acid salt and glycerol. The salt of fatty acid is called soap.

*Saponification process is a hydrolysis reaction.
*Soap is produced by saponification of a triglyceride.
*Soap is a salt composed of a mixture of carboxylate anion and univalent cations.
*Sodium hydroxide produce hard soap.
*Potassium hydroxide produce soft soap.
*Potassium soaps are more soluble than sodium soaps and readily produce lather.

How Soap Clean ?
       The hydrophilic (carboxylate) end of the soap molecules attached to water. The hydrophobic (hydrocarbon chain ) end attached to oil and grease. The more and more soap molecules embedded
into a grease to forming micelles around oil droplets. The hydrophobic ends of the soap molecules attached towards the grease while the hydrophilic ends of the soap face outward into the water, resulting is an emulsion of soapy grease particles suspended in the water. Then the oily particles are easily washed away. The water agitation can help to clean greasy and oil. The micelles are dispersed into the water.

                                          Hydrophilic -  ( water loving )
                                         Hydrophobic- ( water hating )
              Soap do not work well in hard water. Hard water containing calcium and magnesium ions. these ions react with soap to form an insoluble precipitate known as soap film. This precipitate is often seen as a gray line on a bathtub or sink and is often called scum.

Detergents:
       Detergents are similar to soaps. They work in both soft and hard water. The detergent removes the oil film and the dirt can be washed away.

Rusting Of Ion

               Irons form a red-brown stuff that is called rust. Rusting of iron is a chemical process. In this case iron combine with oxygen in the presence of water molecules to form a iron oxide.

Fe   +   O₂   +   H₂O   →   Fe₂O₃.XH₂O

Combustion

             Energetic molecules combine with oxygen to produce carbon-dioxide and water. Combustion reaction is a exothermic reaction. So it release heat.
Example:

C₃H₈   +   5O₂   →   4H₂O   +   3CO₂   +   Energy ( Heat )

            Burning, light a grill, strike a match sticks combustion of propane gas these are the combustion reactions.

Aerobic Respiration

                 Respiration helps to breaks down glucose into carbon-dioxide and water. Energy used by cells is chemical energy in the form of ATP ( adenosine triphosphate ). Aerobic respiration is the opposite process of photosynthesis.

C₆H₁₂O₆+   6O₂   →   6CO₂   +   6H₂O   +   Energy ( 36 ATPs )

Photosynthesis

              Photosynthesis is a chemical reaction by which green plants make their own food. In the presence of sun light carbon-dioxide and water molecule react to form a glucose ( Food ) and oxygen. This is the most common everyday chemical reaction.

6CO₂   +   6H₂O   +   light   →   C₆H₁₂O₆   +   6O₂

Why Smoking Causes Cancer ?

                                          Tobacco smoke contain more than 60 carcinogenic compounds. 4000 individual substances identified in tobacco smoke, including carbon monoxide, hydrogen cyanide, ammonia and other toxic irritants. The main reason is tobacco contains nicotine. Nicotine is a additive content which alters brain functioning.

                                           Nicotine is naturally occurring liquid alkaloids. When a man smoke nicotine is absorbed through the skin and mucosal lining of the mouth and nose and by inhalation int he lungs. In the body it activate the same reward system as do other drugs such as cocaine. in the brain nicotine increases the level of neurotransmitter dopamine. so the brain responsible for feeling pleasure. People continue dosing themselves frequently throughout the day to maintain the pleasurable effects of nicotine and to prevent withdrawal symptoms.

Why do onion make you cry ?

                                   Onion cells contain some chemical compounds like sulfur. Cut the onion its cells are broken and the chemical compounds are released into the air. So that more volatile sulfured products are formed. Sulfured compounds react with the moisture in eyes forming sulfuric acid. Which produce a burning sensation. So that the tears comes out.

How To Avoid ?

• Chop the onion under cold water. The volatile sulfured compounds will be released but then they react  with the water, instead of reaching your eyes.
• You can freeze the onion for 10 minutes before cutting it. The cold temperature of the onion will slow down the chemical reaction which forms the volatile sulfured compounds.

How Soap Clean ?

                           Substance which can be dissolved in water and others that cannot. For example water and oil. water and oil do not mix together. So we try to clean oil stain from a cloth or hand water is not enough. So we need a soap.
                           Soap is formed by a molecules of hydrophilic and hydrophobic. So that soap molecules act like a diplomat, and improving the relation ship between water and oil.

How?
                    When soap is added to the water

• The hydrophilic heads of molecules stay into the water.
• The long hydrophobic chain join the oil.

                      Then they formed circular groups named micelles, with the oil material absorbed inside and trapped. An emulsion of oil in water is then formed after that the oil particles becomes suspended and dispersed into the water. Soap cleans by acting as an emulsifier. It allows oil and water to mix. So that oily grime can be removed during rinsing.