Advertisements
Advertisements
प्रश्न
In a beam of sunlight entering a room, we can sometimes see dust particles moving in a haphazard way in the air. Why do these dust particles move?
Advertisements
उत्तर
When a beam of sunlight enters a room, suspended dust particles are seen moving haphazardly. This is because the dust particles are constantly hit by the fast moving particles of air and due to this remain suspended despite gravity acting on them. This is an example of Brownian motion.
APPEARS IN
संबंधित प्रश्न
Name the terms for the change of vapour into a liquid.
What is meant by saying that non-metals are brittle ?
What is the other name for impure substances ? Give two examples of impure substances.
Name two solid, two liquid and two gaseous elements at the room temperature.
Name a non-metal :
- which is lustrous
- which is required for combustion
- whose one of the allotrophic forms is a good conductor of electricity. Name the allotrope.
- other than carbon which shows allotropy
- which is known to form the largest number of compounds
What are (i) metals (ii) non-metals, and (iii) metalloids ? Give two examples each of metals, non-metals and metalloids.
The elements which normally exist in the liquid state are :
Choose the correct answer.
A 5 per cent sugar solution means that :
State whether the following statement is true or false :
Sponge is an example of solid sol.
Fill in the following blank :
A colloid is a ..............mixture and its components can be separated by the technique known as ...............
Define Aerosol Give one example.
21.5 g of sodium chloride dissolves in 60 g of water at 25°C. Calculate the solubility of sodium chloride in water at that temperature.
When the solid A is added to water, it dissolves with the evolution of a lot of heat and making little explosions to form two products B and C. The properties of products B and C are entirely different from those of solid A as well as water. Moreover, products B and C cannot be reconverted into solid A and water. When another solid D is added to water, it dissolves with the absorption of a little heat to form a product E which cools down. The product E shows the properties of both, solid D as well as water. Moreover, product E can be converted into solid D and water.
(a) What type of change occurs when solid A is dissolved in water ? Why ?
(b) What type of change occurs when solid D is dissolved in water ? Why ?
(c) Name a metal which you think could behave like solid A. Also name the products B and C.
(d) Name the solid D if it is the one which is used in making ordinary dry cells.
(e) Name the process by which D can be recovered from E.
Wipe the board with a duster and then tap the duster against the table. What do you see?
Asmita went to buy an earthen pot. There she saw many things kept for sale.
How did she identify what she needed?
Liquids cannot be compressed and they have fixed volume.
Higher the temperature, the higher the kinetic energy of particles.
Boiling refers to the process by which a substance changes from the liquid to the gaseous state at its ______ point.
Define the term matter.
Define the term matter.
