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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
Convert the following temperature to the celsius scale.
470 K
Give two reasons to justify water at room temperature is a liquid.
What do you observe when :
water is boiled
Dissolving salt in water is a reversible change.
The boiling point of water is 100° C. Express this in SI units (Kelvin scale).
State whether the following statement is true or false :
Solid carbon dioxide is stored under low pressure.
Fill in the following blank with suitable words :
Scientists say that there are actually five states of matter : solid, liquid, gas, .................... and ...................
Which contains more heat, 1 kg of ice of 0° C or 1 kg of water at 0° C ? Give reason for your answer.
Explain why, steam at 100° C is better for heating purposes than boiling water at 100° C.
How is ammonia gas liquefied ?
When heat is constantly supplied by a burner to boiling water, then the temperature of water during vaporisation :
Match the following:
| Column A | Column B |
| (a) Evaporation of water | (i) Non-periodic change |
| (b) Milk turning sour | (ii) Periodic change |
| (c) Earthquake | (iii) Chemical change |
| (d) Change of seasons | (iv) Physical change |
| (e) Glowing of bulb | (v) Reversible change |
Write whether the following statement is true or false:
Solids have the larger inter-molecular space
Name the phenomenon which causes the following changes:
Formation of water vapour from water
Name the phenomenon which causes the following changes:
Conversion of water into steam
A kind of matter which can sublime is
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 will happen if....? And why?
Rubber is not fitted on a pair of tongs.
State which of the three states of matter Le. solids, liquids or gases – have
(a) No definite volume
(b) A definite shape
(c) High density
(d) No free surfaces
(e) Particles – which diffuse very easily.
Give the reason for the following
On heating a sublimable solid, the molecules break free & escape from the surface of the solid directly into vapour.
