Explain why
Water on a clean glass surface tends to spread out while mercury on the same surface tends to form drops. (Put differently ,water wets glass while mercury does not).

Water sticks to glass whereas mercury does not. Explain.

Explain why The angle of contact of mercury with glass is obtuse. While that of water with glass is acute .

Why do we see water droplets on the outer surface of a glass containing ice - cold water?

Why do we see water droplets on outer surface of a glass containing ice - cold water?

To clean their spectacles, people often breathe out on glasses to make them, wet.Explain why the glasses become wet.

Carry out the following osmosis experi ment. Take four peeled potato to halves and scoop each one out to make potato cups one of these potato cups should be made from a boiled potato. Put each potato cup in a tray containing water . Now (a) Keep cup A empty (b) Put one teaspoon sugar in cup B ( c) Put one teaspoon sugar in the boiled potato cup D. Keep these for two hours . The observe the four potato cups and answer the following : M (i) Explain why water gathers in the hollowed portion of B and C . (ii) Why is potato A necessary for the experiment . (iii) Explain why water does not gather in the hollowed out portions of A and D.

Atoms of eight elements A, B, C, D, E, F, G and H have the same number of electronic shells but different in their outermost shells. It was found that elements A and G combine to form an ionic compound which can also be extracted from sea water. Oxides of the elements A and B are basic in nature while those of E and F are acidic. The oxide of elements D is almost neutral. Answer the following questions based on the information given here in : (i) To which group or period of the periodic table do the listed elements belong ? (ii) Which one of the eight elements is likely to be a noble gas? (iii) Which one of the eight elements would have the largest atomic radius ? (iv) Which two elements amongst these are likely to be the non-metals? (v) Which one of these eight elements is likely to be a semi-metal or metalloid ?