CHEMISTRY
1) Convert 250 c to the Kelvin scale
.
What happens to the hest energy which is supplied to the solid once it starts meting.
3What is dry ice? Why is so called? How is it prepared?
* A rubber band can change its shape on stretching will you classify it as solid or not? Justify
your answer.
5) Give reasons :
a) When a solid melts, its temperature remains the same, although the heat is supplied
continuously.
b) Rate of mixing of particular varies with temperature.
c) (CNG) is used as fuel these days in vehicles.
6) a) Co2 is a gas. Write its two gaseous properties to justify it.
b) How can we liquefy a gas?
c) Write the full form of CNG and LPG.
Account for the following:
a) When sugar crystals dissolve in water, the level of water does not rise appreciable.
b) Doctors advise to put strips of wet cloth on the forehead of a person having high fever.
c) Dogs generally hang out their tongue in summer.
8) a) Define diffusion. Explain the rate of order of diffusion in solids, liquids and gases.
b) State the effect of temperature on diffusion.
9) How is rate of evaporation affected by change in the following? Justify your answer by giv
a suitable example in each.
a) Temperature b) Wind speed c) Humidity
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Answers
Answer:
250 c* 273 is equal to 523
Explanation:
When the temperature reaches themelting point, the solid, absorbsenergy and increases its internalenergy. ... At the same temperature, the solid absorbs an energy called the latent heat of fusion to change its state to liquid. After the solid melts, its temperature increases further if more heat is supplied.
Answer: Dry ice is solid carbon dioxide. (Similarly to ice of water) It is called dry ice because, It goes from solid to gaseous state without going to liquid phase i.e., sublimation.
prepration:The carbon dioxide gas is pressurized and cooled to form liquid CO2. Then liquid carbon dioxide is injected into either a block press or pelletizer. These machines have chambers in which, once released to atmospheric pressure, the liquid carbon dioxide converts todry ice snow and carbon dioxide gas.
