13. The ‘sea water’ can be classified as a homogeneous as well as heterogeneous mixture. Comment.Ans :

A mixture which has a uniform composition throughout is called a homogeneous mixture or solution. A mixture which does not have a uniform composition throughout is called a heterogenous mixture. (i) Sea water looks like a single substance, i.e., salt, water and the gases are mixed together so completely that they cannot be differentiated as individual substances. The particles of a solution are smaller than 1 nm (10-9 metre) in diameter. So, they cannot be seen by naked eyes. Therefore, we can classify sea water as homogeneous mixture. (ii) Sea water can be classified as a heterogeneous mixture because when we view it under the microscope we can find bits of dirt, and other impurities like mud, decayed plant, etc. floating in it. It is mixture of many salts, water and other many impurities. Apart from these, many gases (air) are also dissolved in sea water. Because of salt and some other bigger size of impurities, sea water is classified as heterogeneous mixture.