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प्रश्न
Mention a change which is always desirable.
उत्तर
Changes that are useful to man are desirable changes, e.g., change of milk into curd.
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संबंधित प्रश्न
Name A, B, C, D, E and F in the following diagram showing change in its state.
Name the temperature at which :
- a liquid changes into a gas.
- a solid changes into a liquid.
What is the name of the process in which a gas turns directly into a solid ?
Why is solid carbon dioxide known as dry ice ?
How is ammonia gas liquefied ?
Define the term 'latent heat of fusion' of a solid. How much is the latent heat of fusion of ice ?
On converting 25°C, 38°C and 66°C to Kelvin scale, the correct sequence of temperatures will be :
Which of the following factors are responsible for the change in state of solid carbon dioxide when kept exposed to air ?
- increase in pressure
- ncrease in temperature
- decrease in pressure
- decrease in temperature
Define: cohesive force
Differentiate between: Melting and boiling
Give reasons:
How is interconversion of states of matter different from chemical reaction?
Name the phenomenon which causes the following changes:
Formation of water vapour from water
Name the phenomenon which causes the following changes:
Disappearance of camphor when exposed to air
State which of the following statement is true or false. If false write the correct statement.
The conversion of water to ice is called freezing.
What is it made from? Why?
The sheets used for roofing.
What will happen if....? And why?
Rubber is not fitted on a pair of tongs.
Fill in the blank with the appropriate word of the statement given below:
Change of milk of curd is a _______ change.
Select the correct answer from A, B, C, D & E for the statement given below:
The state of matter which has ___________ least density & no free surfaces.
Give the reason for the following:
The kinetic energy of molecules of gases is very large & of solids, the least.
Prepare a model to demonstrate movement of particles in solids, liquids and gases.
For making this model you will need
- A transparent jar
- A big rubber balloon or piece of stretchable rubber sheet
- A string
- Few chickpeas or black gram or dry green peas.
How to make?
- Put the seeds in the jar.
- Sew the string to the centre of the rubber sheet and put some tape to keep it tied securely.
- Stretch and tie the rubber sheet on the mouth of the jar.
- Your model is ready. Now run your fingers up and down the string by first tugging at it slowly and then rapidly.
