The photoelectric effect refers to the emission, or ejection, of electrons from the surface of, generally, a metal in response to incident light. Energy contained within the incident light is absorbed by electrons within the metal, giving the electrons sufficient energy to be 'knocked' out of that is emitted from the surface of the metal.

Tritium, also known as hydrogen-3) is a radioactive isotope of hydrogen. The nucleus of tritium (sometimes called a triton) contains one proton and two neutrons, whereas the nucleus of protium (by far the most abundant hydrogen isotope) contains one proton and no neutrons.

The mineral pyrite, or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula FeS₂. This mineral's metallic luster and pale brass-yellow hue give it a superficial resemblance to gold, hence the well-known nickname of fool's gold. After burning pyrites ore Sulphur dioxide gas is produced.

By specific energy of hydrogen (140 KJ/Gm) is the Hydrogen is the best fuel in terms of energy released per gram of fuel. However, vehicles must inherently carry their fuel supply, so to determine which fuel is best for motor vehicles; energy density of the fuel is the next measurement.

Bleaching powder is powder that contains calcium chloride and calcium hypocrite which is used in the solution as a bleaching agent.

It is prepared by passing gas state of chlorine over dry slaked lime.

The Dumas method in analytical chemistry is a method for the quantitativedetermination of nitrogen in chemical substances based on a method first described by Jean-Baptiste Dumas in 1826.

Resin is an adhesive inflammable substance insoluble in water. It is extracted from fir or pine.

Sublimation is the transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase.

Electronegativity increases down the group and decreases down the period.
Electronegativity of the elements using the Pauling Scale is as follows: 

1. Fluorine: 3.98


2. Oxygen: 3.44


3. Chlorine: 3.16


4. Sodium: 0.93.

• Adding carbon to iron to make steel does make it stronger and tougher, up to a point. Then it will get stronger but less tough.


• The percentage of carbon in steel is 0.5 to 1.5.