source : online-sciences.comSubstance made up of two or more elements chemically combined in a fixed proportion by weight. Ex . Water always contains hydrogen and oxygen in the ratio 1 : 8 by weight. Carbon dioxide contains carbon and oxygen in the ratio of 12 : 32 or 3 : 8. Properties of substances-When solid is being beaten then it is converted into sheet .This property of solid is called Malleability. Ex- copper , silver , gold , aluminium and iron are malleable in nature. It is the property of metal to be drawn into wires. Ex- copper , silver , gold , aluminium and iron are ductile in nature. It is the property of solid substances due to which solid does not come back to its original shape, size or volumeafter the deforming force is removed. It is the property of solid substances in which solid regain to its original shape, size or volume after the deforming force is removed. Compounds combine with moisture of atmosphere and get converted into hydroxides or hydrates. Such compounds are called hygroscopic. Ex- anhy. CuSO4, anhy. FeSO4, anhy. Na2CO3 , quick lime are hygroscopic in nature. Some compounds absorb moisture of atmosphere and become wet. These compounds are called deliquescent. Ex- Anhy. MgCl2, Anhy. CaCl2, NaOH and KOH are deliquescent in nature. Some crystalline solid loses their water of crystallisation on exposure and becomes powdery. Such compounds are called efflorescent. Ex- Na2CO3.10H2O (washing soda), Na2SO4.10H2O (Glauber’s salt) , K2SO4. Al2(SO4)3. 24 H2O (potash alum) are efflorescent compound. When solid is converted into small pieces on hammering. Then compound is called brittle. A material is said to be harder than the other if it can scratch it. Hardness is measured in Moh’s scale. For this purpose , ten materials have been selected and assigned hardness from 1 to 10.