How a match box works?

Red phosphorus is used in the striking strips on match boxes. When a match is struck, potassium chlorate in the match head mixes with some red phosphorus on the striking strip, and the friction is enough to ignite this mixture.

How invisible ink works?

Cobalt(2) chloride hexahydrate, dissolves readily in water to give a red solution. If we use this solution as an “ink”, we can write secret message on paper. The writing is not visible when the water evaporates form the paper. When the paper is heated, however the message can be rad.
If you don't want to be entangled in the science and just want to write with such magic ink, just use juice of onion as a ink. To read the massage again heat the paper. And enjoy yourself !

For an another interesting trick, go to the page 'Fun Creation'.

Why plaster of Paris used in designing the houses.

When POP is added to water, it forms a thick slurry that can be poured into a mold. As it takes on more water, the material increases in volume and forms a hard, inflexible solid. This property makes palster of Paris a useful material for artists, because the expanding compound fills a mold completely and makes a high quality reproduction.