Tuesday, 16 July 2019

9th class Chemistry Notes Chapter 5 - MCQs,Questions and Practicals pdf

Matric 9th Chemistry Notes Chapter 5 - MCQs,Questions and Practicals
Here are the Matric 9th Chemistry Notes Chapter 5 Physical States of Matter - MCQs,Questions and Practicals. It Includes short questions, Long question and Practical Questions pdf download and view online.

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 Differentiate between diffusion and effusion.
 Ans. Diffusion:
 "Diffusion is defined as spontaneous mixing up of molecules by random motion and collisions to form a homogeneous mixture.
 "It is escaping of gas molecules through a tiny hole into a space with less pressure.
(ii) Define compressibility of gases. Why gases are compressible?
 Ans. Compressibility of Gases:
 "When we put some pressure on gases, their volume decreases. This is called compressibility of gases Compressibility of
 Gases: Gases are highly compressible due to empty spaces between their molecules. When the gases are compressed, the molecules come closer to one another and occupy less volume as compared to the volume in uncompressed state.
 (iv) Define standard atmosphere pressure. What are its units?
 Ans. Standard Atmospheric Pressure
 It is the pressure exerted by the atmosphere at the sea level
 "It is defined as the pressure exerted by a mercury column of 760 mm height at sea level.
 Units of Pressure:
 (1) Pascal 
(2) atm
 (3) torr
 What is meant by mobility of gases? Why gases are mobile?
 Mobility of Gases:
 "Gas molecules can move from one place to another within the container. This is called mobility of gases Cause of Mobility of gasses
 Gas molecules are in continuous state of motion. They have high kinetic energy and thus, can move from one place to another within the container. That is why gases are mobile
(vi) Why does volume of a gas decrease with increase of pressure?
 Ans. The volume of a gas decreases with increase of pressure.
 This is because, large empty spaces are present between the gas molecules. When pressure is applied on a gas, the gas molecules come close to each other. Kinetic energy and attractive forces start dominating. That is why the volume of a gas decreases with increase of pressure.
 When gas is allowed to effect on its temperature 2p and, what will be its 
Ans According to Charles' law the volume of a given mass of a gas is directly proportional to the absolute temperature provided the pressure is kept constant." Thus, when a compressed gas is allowed to expand into a region of low pressure, it gets hot.
 (viii) Is the Boyle's Law valid at very high temperature?
 Ans. The Boyle's law is valid at very high temperature. It is because, in Boyle's law temperature is kept constant.
 (ix) What will happen if the pressure on a sample of gas is raised three times and its temperature is kept constant?
 Ans. If the pressure on a sample of gas is raised three times and its temperature is kept constant, then its volume will reduce to three times (.e. it will reduce to times).
 Define evaporation. How it is affected by surface area?
 Ans. Evaporation:
 "The process of changing of a liquid into a gas phase is called evaporation
 Effect of Surface Area on Evaporation: Evaporation is a surface phenomenon. Greater is surface area, greater is evaporation and vice versa.
 For example, sometimes a saucer is used if tea is to be cooled quickly. This is because evaporation from the larger surface area of saucer is more than that from the smaller surface area of a tea cup.
 Differentiate between evaporation and condensation.
 Ans. Evaporation is reverse to condensation in which a liquid changes into gas contrary to condensation in which a gas changes to liquid.
 (ii) Why evaporation causes cooling?
 Ans. Evaporation is a cooling process. When the high kinetic energy molecules vaporize, the temperature of remaining molecules falls down. To compensate this deficiency of energy, the molecules of liquid absorb energy from the surroundings. As a result the temperature of surrounding decreases and we feel cooling.
 For example, when we put a drop of alcohol on palm, the alcohol evaporates and we feel cooling effect
 (iv) Define boiling point. What is the effect of external pressure on boiling point?
 Ans. Boiling Point: "The temperature at which the vapour pressure of a liquid becomes equal to the atmospheric pressure or any external pressure is called boiling point.
 Effect of External Pressure:
 Boiling point of a liquid depends upon external pressure.
 Boiling point of a liquid is controlled by external pressure in such a way, that it can be increased by increasing external pressure and vice versa. This principle is used in the work of Pressure Cooker'
 (v) Define vapour pressure. What is the effect of temperature on vapour pressure?
 Ans. Vapour Pressure
 "The pressure exerted by the vapours of a liquid at equilibrium with the liquid at a particular temperatures called vapour pressure of a liquid.
 Effect of Temperature on Vapour Pressure: At high temperature, vapour pressure is higher than at ow temperature. At elevated temperature, the kinetic energy of the molecules increases enough to enable them to vaporize and exert pressure.
 (vi) What is the relationship between evaporation and boiling point of a liquid?
 Ans. Relationship b/w Evaporation and Boiling Point: When a liquid is heated, its molecules gain energy. The number of molecules which have more than average kinetic energy increases More and more molecules become energetic enough to overcome the inter molecular forces. Due to this, rate of evaporation increases that results in increase of vapor pressure until a stage reaches where the vapor pressure of a liquid becomes equal to atmospheric pressure. At this stage the liquid starts boiling. This the relationship b/w evaporation and vapour pressure.

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