A physical change can be distinguished from a chemical change because this happens in a physical change: a) The properties of the substance may change, but no new substances are produced. b) The properties of the substance change for only a short time but will return to their original state. c) An entirely new substance with new properties forms as a result of the change. d) A new substance is produced, but the new substance has properties identical to the original substance.

a gas, having a molecular weight of 13 kg/kmol and a kinematic viscosity of 0.25 cm2/s, flows through a pipe 0.25 m internal diameter and 5 km long at the rate of 0.4 m3/s and is delivered at atmospheric pressure.

c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.