VIBHAVARI VATS (ROLL NO-16)

          

           THIS IS MY HOMEWORK PAGE.I WILL DO MY HOMEWORK REGULARLY.

                 ch-1:-  MATTER IN OUR SURROUNDING 

QUESTION :-   Why do we observe that level of water does not change even

                     after the dissolving of salt in it?

ANSWER:-    Level of water do not change even after dissolving the salt because there is space between the particles of water and the when we dissolve salt in water the particles of salt gets filled or adjusted in between the particles of water and thus the level of water do not change.

DATE :- 4 April,2016

                                    PROPERTIES OF PARTICLES

• The particles of matter are very small

• The particles of matter are continuously moving means they have kinetic energy.

• The particles of matter have space between them. 

  DATE :- 5 April,2016  

                                          DATE :- 6 April,2016

  Solid has a fixed shape and a definite volume. The molecules in a solid are in fixed positions and are close together. Although the molecules can still vibrate, they cannot move from one part of the solid to another part. the force of attraction is very high in solid that is why it maintains its shape.  

                                                  EXERCISE

    Question1:- Convert the following temperatures to Celsius scale.
        
                         (a) 300 K                                                (b) 573 k
  Answer:- Kelvin is SI unit of temperature, where 0°C = 273.16K
                                          (a) 300 K = 300 − 273 Celsius
                                         °C = 27 °C
                                          (b) 573 K = 573 − 273 Celsius
                                        °C = 300 °C
  Question2:-  Convert the following temperatures to Kelvin scale.
                                    (a) 25°C                                            (b) 373°C
  
  
  Answer:- Kelvin is SI unit of temperature, where 0°C = 273.16K
                           (a) 25 °C = 25 + 273 K
                                            = 298 K 
                        (b) 373 °C = 373 + 273 K 
                                              = 646 K
  Question3:-Give reason for the following observations. 
                    
  (a) Naphthalene balls disappear with time without leaving any solid
  Answer:-Naphthalene balls disappear with time because                                  sublimation takes place there and naphthalene balls get  converted into vapours without coming in its liquid form.
    
  (b) We can get the smell of perfume sitting several metres away. 
  Answer:- Gaseous particles possess high speed and large spaces between them. Particles of perfume diffuse into these gaseous particles at a very fast rate and reach our nostrils. This enables us to smell the perfume from a distance
  
  
  Question 4 :-Arrange the following substances in increasing order of forces of attraction between particles−− water, sugar, oxygen.
  
  answer:-                Oxygen < Water < Sugar Question 5: What is the physical state of water at - 
  (a) 25°C 
  (b) 0°C 
  (c) 100°C
  
  answer:-  (a) 25°C - Water at 25°C is present in the liquid state.
  (b) 0°C - solid or liquid state.
  (c) 100°C - vapour or liquid state.
  
  Question 6: Give two reasons to justify− 
  (a) water at room temperature is a liquid.
   (b) an iron almirah is a solid at room temperature. answer
  
  answer:-) At room temperature (25 °C), water is a liquid because it has the following characteristic of liquid: 
  .
  (i) At room temperature, water has no shape but has a fixed volume that is, it occupies the shape of the container in which it is kept.
  
  (ii) At room temperature, water flows
  
  
  
  (b) An iron almirah is a solid at room temperature (25 °C) because: (i) it has a definite shape and volume like a solid at room temperature.
   (ii) it is rigid as solid at room temperature.
  Question 7: Why is ice at 273 K more effective in cooling than water at the same temperature? 
  
  Answer : Ice at 273 K has less energy than water (although both are at the same temperature). Water possesses the additional latent heat of fusion. Hence, at 273 K, ice is more effective in cooling than water
  
  Question 8: What produces more severe burns, boiling water or steam?
  
   Answer : Steam has more energy than boiling water. It possesses the additional latent heat of vaporization. Therefore, burns produced by steam are more severe than those produced by boiling water

                                                               

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