A metal is a material (an element, compound, or alloy) that is typically hard, opaque, shiny and has good electrical and thermalconductivity.

Citric acid is a weak organic acid with the formula C₆H₈O₇.The juiceof the lemon is about 5% to 6% citric acid, which gives a sour taste.

A pure element is a chemical element consisting of only one stableisotope.

Radioactive substances are continually producing three kinds of dangerous radiation, alpha particles, beta particles and gamma rays. These types of radiation are invisible to the naked eye and so you won't see a green glow.

Bleaching powder or Calcium Hypochlorite is a chemical compound with formula Ca (CIO)₂ . It is widely used for water treatment and as bleaching agent (bleaching powder). This chemical is considered to be relatively stable and has greater available chlorine than Sodium Hypochlorite (liquid bleach). It is prepared by either calcium process or sodium process.

A reaction inhibitor is a substance that decreases the rate of, or prevents, a chemical reaction.

Hydrogen fuels causes minimum environmental pollution. Hydrogen was discovered by Henry Cavendish. Hydrogen is a flammable, colourless, compressed gas packages in cylinders at high pressure. Hydrogen gas is not a Green House Gas.

Catalysisis the increase in the rate of a chemical reaction due to the participation of an additional substance called a catalyst. Name of of the catalysis was given by Berzelius.

A bullet-proof material is made of polyethylene. Polyethylene molecules are long chains that can be branched or straight. The length and straightness of the chains and the purity of the plastic determines how strong it is. High grade polyethylene has been used to make bulletproof vests.

A metal is a material that is typically hard, opaque, shiny and has good electrical and thermal conductivity. Copper is an element with symbol Cu and atomic number 29.