Science: Matter In Our Surroundings

Q1. Define matter.
Answer: Anything that occupies space and has mass is known as matter.

Q2. What are the characteristics of matter?
Answer: A large number of particles together constitute matter.
a. These particles are of very small size.
b. Particles of matter have spaces among them.
c. Particles of matter are in continuous motion i.e. they possess kinetic energy.
d. Particles of matter attract each other i.e. inter particle forces of attraction or inter molecular forces.

Q3. How matter is classified in terms of physical state?
Answer: solid, liquid and gas.

Q4. How matter is classified in terms of composition?
Answer: element, compound and mixture.

Q5. Define Density.
Answer: The mass per unit volume is called density. Its SI unit is Kgm-3.

Q6. What do you mean by the term Volume?
Answer: The space occupied by a substance is known as volume.

Q7. What do you mean by the following terms:
 a. Evaporation
 b. Sublimation
 c. Condensation
Answer:
a. The process of liquid changes into vapors on heating even below its boiling point is known as evaporation.
b. Sublimation: The changing of the solid directly into vapors on heating and vapors into solid on cooling.
c. The process at which vapors changes into liquid is termed as condensation.

Q8. Define Latent Heat of Fusion and Latent Heat of vaporisation.
Answer: The latent heat of fusion of a substance is the quantity of heat required to convert one unit mass of the substance from solid state to the liquid state at its melting point without any change of temperature.
The quantity of heat required to convert one unit mass of a liquid into vapour at its boiling point without any change of temperature is called its latent heat of vaporisation. It may also be denied as the amount of heat consumed when 1 kg of liquid changes into vapor at constant temperature.

Q9. Define the term Volatile Liquid.
Answer: Those liquids which can change into vapours easily are termed as volatile liquids.

Q10. Define the following terms:
 a. Melting point
 b. Freezing point
 c. Boiling point
Answer:
a. Melting Point: The temperature at which solid changes into liquid is called its melting point.
b. Freezing Point: The temperature at which liquid changes into solid.
c. Boiling Point: The temperature at which liquid changes into vapors is termed as its boiling point.

Q11. Which of the following are matter?
Chair, Air, Love, Smell, Hate, Almonds, Thought, Cold, Cold drinks, Smell of perfume
Answer:  Anything which occupies space, mass and can be felt by human senses are called matter. So the things from the above list which are matter are:
1. Chair
2. Air
3. Smell
4. Almonds
5. Cold drink
6. and Smell of a perfume (It is also considered in matter because it is due to the presence of some volatile substance in air).
Objects which are not matter from the above list are: Love, hate, Thought and Cold.

Q12. Give reasons for the following observations. The smell of hot sizzling food reaches you several meters away, but to get smell from cold food you have to go close.
Answer: Particles present in the matter possess kinetic energy and therefore move constantly. At lower temperature, particles have low kinetic energy and thus move slowly. But as soon as the temperature rises, these particles move faster than when they were in cold. As the particles of hot vapors coming out of hot sizzling food move faster, they can reach several meters away. The particles in the cold food move slowly and thus do not reach us when we are away even a few meters. Therefore we have to go closer to smell cold food.

Q13. Why do gases diffuse rapidly?
Answer: The gases diffuse rapidly because the particles in the gases can freely move in all directions and there is lot of inter molecular space in gases.

Q14. The mass per unit volume of a substance is called density (density=mass/volume). Arrange the following in order of increasing density:
Air, Exhaust from chimneys, Honey, Water, Chalk, Cotton and Iron.
Answer: The order in increasing density is:
Air
Exhaust from chimneys
Cotton
Water
Honey
Chalk
Iron

Q15. Define evaporation.
Answer: Evaporation is a physical process in which a liquid changes to its gaseous state, at a temperature lower than its boiling point.

Q16. Explain compressibility in gases with an example?
Answer: Liquefied petroleum gas (LPG) cylinders are used in our homes for cooking, contains gases in the compressed state. Similarly, compressed natural gas (CNG) is used as a fuel in vehicles. Large volumes of gases can be compressed in small cylinders and are transported to distant places.

Q17. What is SI unit of temperature? Give mathematical relation also.
Answer: SI unit of temperature is Kelvin. T (K)= T (°C) +273

Q18. Convert the following temperature to Celsius scale:
(a) 300 K
(b) 573 K
Answer: (a) 300K = 300 – 273 = 27 °C
(b) 573 K = 573 – 273 = 300 °C

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