States of Matter

5.41. Ideal Gas: A gas that follows Boyle's law, Charles' law and Avogadro law strictly, is called an ideal gas. It is assumed that intermolecular forces are not present between the molecules of an ideal gas.

Real Gases: Gases which deviate from ideal gas behaviour are known as real gases. NH₃ is exp

5.40. (a) Surface tension: It is defined as the force acting per unit length perpendicular to the line drawn on the surface.

(b) Surface tension of a liquid depends upon following factors.

(i) Temperature: Surface tension decreases with rise in temperature. As the temperature of the liquid

5.39. In liquids, the molecules are more compact in comparison to gases.

5.38. The temperature at which a real gas obeys ideal gas law over an appreciable range of pressure, is called Boyle temperature or Boyle point.

5.37.  (i) Surface tension decreases with increase of temperature.

(ii) Viscosity decreases with increase of temperature.

5.36.  Avogadro law states that equal volumes of all gases under same conditions of temperature and pressure contain equal number of molecules.

Dalton's law of partial pressure states that total pressure exerted by a mixture of non-reacting gases is equal to the sum of partial pressures exerted

5.35. When density of liquid and vapours becomes the same; the clear boundary between liquid and vapours disappears. This temperature is called critical temperature.

5.34. The temperature at which the vapour pressure of a liquid is equal to external pressure is called boiling point of liquid.

5.33. Molecules of liquids are held together byattractive intermolecular forces. Liquids havedefinite volume because molecules do notseparate from each other. However, moleculesof liquids can move past one another freely, therefore, liquids can flow, can be poured andcan assume the shape of the

5.32.  (c) F₂