Give reasons for the following:

1. Solids have a definite shape or Volume.

2. Liquids have one free upper surface only.

3. Globules of mercury kept in a petri dish, which is shaken slowly, come together forming a big globule.

4. A crystal of Iodine on slow heating in a closed flask, turns into vapours & fills the complete flask.

5. An empty tumbler lowered into a glass beaker containing water, on tilting shows bubbles of air coming out, but when not tilted, no bubbles are seen.

1. Solids have negligible intermolecular space as the molecules are closely packed and the force of attraction is maximum. This arrangement of molecules gives them a definite volume and a definite shape.

2. Due to large intermolecular spaces and weaker intermolecular force of attraction, liquids have a definite volume but no definite shape. As a result, a liquid takes the shape of the container in which it is kept. So the top surface of the container is the only free upper surface it has.

3. The intermolecular force of attraction between the particles of mercury causes the globules of mercury to come together and form a big globule when the petri dish is shaken slowly.

4. Particles of iodine when heated turn into vapours, which is in gaseous state. Particles of gas are least closely packed and fill the flask.

5. The empty tumbler contains air inside it. When it is lowered into the glass beaker and tilted, water enters the tumbler and pushes out the air inside it which is seen escaping in the form of air bubbles coming out of water. When the tumbler is not tilted, water cannot enter the tumbler so the air inside it is not displaced and no bubbles are seen.