Question:
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 vapours 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.
Matter in Our Surroundings
Q 1.
What is SI unit of temperature? Give mathematical relation also.
Q 3.
What do you mean by change in state?
Q 4.
How matter is classified in terms of physical state?
Q 5.
What are the ways a gas can be liquefied?
Q 6.
Which state of matter is most easily compressible?
Q 7.
What is evaporation? Why does evaporation cause cooling?
Q 8.
Define the term Volatile Liquid.
Q 9.
What do you mean by the term Volume?
Q 10.
List any five physical properties of liquids.
Q 11.
Why solids cannot be compressed like gases?
Q 12.
Define transpiration.
Q 13.
Arrange the following substances in increasing order of intermolecular force of attraction: water, sugar, oxygen
Q 15.
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.
Q 16.
What do you mean by the following terms:
a. Evaporation
b. Sublimation
c. Condensation
Q 17.
What are the differences between boiling and evaporation?
Q 18.
Define Latent Heat of Fusion and Latent Heat of vaporisation.
Q 19.
Define evaporation.
Q 20.
Our own bodies contain examples of all three states of matter. Can you identify these?
Q 21.
How matter is classified in terms of composition?
Q 22.
Why is light not considered matter?
Q 23.
How can matter change its state?
Q 24.
How vapour is different from gases? Give examples of each.
Q 25.
Why do diffusion become faster at higher temperatures?
Q 26.
In which case evaporation of water will be faster i.e. near the sea or far away from the sea.
Q 27.
Which of the following state does not exist at room temperature conditions: a) Solids b) Liquids c) Gas d) Plasma
Q 28.
What is the physical state of water at the following temperatures? (a) 25 °C (b) 0 °C (c) 100 °C
Q 29.
Which of the following are matter?
Chair, Air, Love, Smell, Hate, Almonds, Thought, Cold, Cold drinks, Smell of perfume
Q 30.
Why do gases diffuse rapidly?
Q 31.
Convert the following temperature to Celsius scale: (a) 300 K (b) 573 K
Q 32.
Why does the temperature of a substance remain constant during melting and boiling even when heat is being supplied to it continuously?
Q 33.
Explain compressibility in gases with an example?
Q 34.
Name the process by which a drop of ink spreads in a beaker of water.
Q 35.
Why is ice at 273 K more effective in cooling than water at the same temperature?
Q 36.
What factors affect the rate of evaporation?
Q 37.
Convert the temperature of 373°C to the Kelvin scale.
Q 38.
What are the characteristics of matter?
Q 39.
The Kelvin temperature is 270 K. What is the corresponding Celsius scale temperature ?
Q 40.
The Kelvin scale temperature is 0 K. What is the corresponding Celsius scale temperature ?
Q 41.
Define the following terms:
a. Melting point
b. Freezing point
c. Boiling point
Q 42.
Convert the following temperatures:
a. -78.0 °C to Kelvins
b. 775 K to °C
c. 489 K to °C
d. 24 °C to kelvins
Q 43.
What causes evaporation?
OR
Explain evaporation and its cooling effect in terms of kinetic energy of particles.
Q 44.
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.
Q 45.
Why do solids expand a bit on heating and contract a bit on cooling?
Q 46.
The boiling point of water is 100°C. Express this in SI units (Kelvin scale).
Q 47.
Give the usual name for the following :Heat required to change the state of a substance without changing the temperature.
Q 48.
State whether the following statement is true or false : Solid carbon dioxide is stored under low pressure.
Q 49.
Explain with an experiment to show gases do not have fixed shape or volume.
Q 50.
Honey is more viscous than water. Can you suggest why ?
