a white powder which is to make casts to support fractured bones when mixed with water turns into a hard solid mass. why does it show this behaviour?

a white powder which is to make casts to support fractured bones when

1.	a white powder which is to make casts to support fractured bones when mixed with water turns into a hard solid mass. why does it show this behaviour?
Answer» he white powder is plaster of PARIS(calcium sulphate hemi hydrate)with the formula CASO4. 1/2H2O..when this powder is mixed with water, it gains 1 and a half molecules of water and forms a hard SOLID mass called gypsum [CaSO4. 2H2O].Hope this HELPS you...