72.
Electrical burns occur principally because of

75.
As water is cooled from 4 deg C to 0 deg C, its density

76.
Fish and other aquatic creatures can live inside a deep frozen pond because

77.
The density of a gas is maximum at

78.
Lakes freeze in cold countries in winter, leaving the water underneath at

79.
A bimetal made copper and iron strips welded together is straight at room temperature. It is held vertically with iron strip towards left and copper strip towards right. If this bimetal is heated, it will

80.
Thermal expansion of materials arises from