Why do the gases exert more pressure on the walls of the container than the solids

• Answer:

                    In gases, the particles move randomly at high speed and they collide with each other and also with the walls of container. Thus, they exert . more pressure on the walls of container than solids.                       
  

warning Report Error

Page 2

• Answer:

                                       Diffusion is the process by which a drop of

  
  spreads in a beaker of water.
  

warning Report Error

Page 3

• Answer:

                    Boiling point decreases when atmospheric pressure decreases because boiling point is the temperature at which vapour pressure of a liquid becomes equal to atmospheric pressure.
  

warning Report Error

Page 4

• Answer:

                    When pressure is applied on the surface of ice, the change into liquid is assisted. Thus, melting point decreases.
  

warning Report Error

Page 5

• Answer:

                    Generally for solids, melting point increases with the increase in pressure.
  

warning Report Error

Page 6

• Answer:

                   

  
  
  

warning Report Error

Page 7

• Answer:

                    On applying low temperature, the kinetic energy of the particles decreases and the particles come closer. Increased pressure also brings the particles closer, so the gases liquefy. Hence, the conditions are low temperature and high pressure.
  

warning Report Error

Page 8

• Answer:

                    Evaporation of water increases with increase in temperature because high temperature increases the kinetic energy of water molecules so water molecules present at the surface leave the surface faster.
  

warning Report Error

Page 9

• Answer:

                    Particles of benzene vapours are more energetic because these have absorbed extra energy in the form of latent heat of vaporisation.
  

warning Report Error

Page 10

• Answer:

                    Liquefied Petroleum Gas (LPG) and oxygen in liquefied form.                    
  

warning Report Error

Page 11

• Answer:

                    (i) It is also known as sublimation.             (1) (ii) The amount of heat energy required to change 1kg of a solid into liquid at atmospheric pressure at its melting point is known as the latent heat of fusion.             (1)                     
  

warning Report Error

Page 12

• Answer:

                    Diffusion is the process in which molecules of a substance move from the place of (their) higher concentration to the place of lower concentration.                                                   (1) But during osmosis, the water (or solvent) molecules move from (their) higher concentration to the place of their lower concentration through a semi permeable membrane. Thus, osmosis is termed as a special kind of diffusion.                                (1)
  

warning Report Error

Page 13

• Answer:

                    When ice melts, it absorbs the energy equal to the latent heat effusion from the surroundings therefore causes cooling effect. But steam releases the extra heat (equal to the latent heat of vaporisation) which it has absorbed when water was converted into steam. So, steam produces severe burns.   (2) 
  

warning Report Error

Page 14

• Answer:

                     The two reasons to justify that carbon dioxide is a gas are (i) Carbon dioxide does not have a fixed volume. It can be compressed on applying pressure.                                                           (1)   (ii) Carbon dioxide does not have a fixed shape. It can take the shape of the container in which it is filled.                                           (1)
  

warning Report Error

Page 15

• Answer:

                    The solutions of both the beakers turned blue after some time. But the colour change was observed earlier in beaker A containing hot water as compared to beaker B containing cold water. This happened due to the faster rate of diffusion at a higher temperature.    (2)
  

warning Report Error

Page 16

• Answer:

                    Take approximately 50 mL of hot tea or water in a cup and also the same quantity of the same hot liquid in a saucer too. It is observed that the liquid in the saucer cools faster than that in the cup. This happened due to increase in the surface area of the liquid in the saucer as compared to the cup. This proved that rate of evaporation increases with increase in surface area.       (2)
  

warning Report Error

Page 17

• Answer:

                      Steam causes more severe burns than boiling water. The reason is that it releases the extra amount of heat (latent heat) which it has already absorbed during vaporisation (at the time of formation of steam from water).     (2)   
  

warning Report Error

Page 18

• Answer:

                                                (i) Water can be changed from gaseous state to liquid state by passing the water vapour through a water condenser as used in case of simple distillation.                                            (1) (ii) Activity Take ice cold water in a glass.  Observe the outer surface of the glass. You find small droplets of water on it. These water droplets are the result of condensation of water vapour present in the air to form liquid water.                                                                  (1)
  

warning Report Error

Page 19

• Answer:

                    The substances are not classified only by their appearance. These are classified by their properties such as density, boiling point or melting point, conductivity, thermal capacity and other chemical properties. Sugar and sodium chloride have different physical and chemical properties and so are they different substance.                                                          (2)
  

warning Report Error

Page 20

• Answer:

                    Similarity Both liquids and gases are fluids and assume the shape of the container.             (1) Dissimilarity A gas can be compressed easily whereas a liquid cannot. A small quantity of gas can fill an entire given container. Also large quantity of a gas can be contained in a small space. A given amount of a liquid has a fixed volume at a given temperature.           (1) 
  

warning Report Error

Page 21

Page 22

• Answer:

                    The gaseous state of a substance can be regarded as vapours only in case it is a liquid at room temperature. Since ammonia is a gas at room temperature, its gaseous state cannot be regarded as vapours.                   (2) 
  

warning Report Error

Page 23

• Answer:

                               The conditions in which the distance between the molecules of hydrogen gas would increase are given below (i) Hydrogen leaking from the container leave some vacant space inside the container, thus distance between the molecules increases. (1)                                    (ii) If volume of the container is increasing, then also gas molecules will get some more space as gaseous molecules occupy all the space available to them.                                (1)
  

warning Report Error

Page 24

• Answer:

                    (B) and (Q are both liquids at room temperature. However (B)'s boiling point is quite close to the room temperature and it is, therefore volatile.                                          (2)
  

warning Report Error

Page 25

• Answer:

                    Lighter gases diffuse faster. Molecular mass of

  
   =12 + 2 x 16 =  44 u Molecular mass of
  
   =12 + 4 x 1 = 16u So, methane
  
  gas would diffuse faster.
  

warning Report Error

Page 26

• Answer:

                    Two ways in which melting and boiling points can be useful are (i) to check whether the substance is pure or not and                                                          (1)           (ii) to identify and characterise the substance.
  

warning Report Error