Question

1. On changing which of the following, the states of matter can be changed ?
(A) Temperature
(B) Pressure
(C) (A) & (B) both
(D) None of these
2. Melting & freezing point of water -
(A) are same
(B) have large difference between them.
(C) have close difference between them. (D) None of these
3. The boiling point of alcohol is 780C. What will be the temperature in Kelvin scale?
(A) 373 K
(B) 351 K
(C) 375 K
(D) 78 K
4. Latent heat of vaporisation of water is -
5. S.I. unit of temperature is -
(A) Kelvin (B)Celsius (C) Both
(D) None
6. In sublimation process -
(A) solid changes into liquid
(B) liquid changes into gas.
(C) solid changes directly into gas.
(D) None of these
clied​

Answer 1

1. The correct answer is options C) (A) & (B) both

• Matter changes from one state to another by changing temperature and pressure.
• For example, when heated, solids become liquids, when heated, liquids become gases.

2. The correct answer is option A) are same

• Because the melting point and the freezing point describe the same transition of matter, in this case from liquid to solid (freezing) or equivalently from solid to liquid (melting).
• What you may not know is that when water freezes or melts, its temperature does not change.

3. The correct answer is option B) 351 K

• The Celsius scale is equivalent to 351 K on the Kelvin scale.

4. Latent heat of vaporisation of water is

• For example, the heat of vaporization of water is 540 cal/g and the heat of freezing of water is 80 cal/g.

5. The correct answer is option A) Kelvin

• The SI unit of temperature according to the International System of Units is Kelvin, represented by the symbol K.
• The Kelvin scale is widely recognized or used in science and engineering. However, in most parts of the world, the Celsius or Fahrenheit scale is used to measuring temperature.

6. The correct answer is option (C) solid changes directly into gas.

• We can define sublimation as the transition of a substance from the solid phase to the gas phase without going to the liquid phase.
• This process is an endothermic phase transition that occurs at a temperature and pressure below the triple point of the substance.

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Answer 2

Answer:

1. On changing the temperature and pressure, the states of matter can be changed.

• On changing the temperature of solids, they are converted into liquids.
• Similarly, on changing the temperature of liquids, they are converted into gases.
• Also, gases when compressed by the application of pressure, get converted back into liquids.
• Hence, the correct option is (C) (A) & (B) both.

2. The melting and freezing points of water (A) are the same.

• The melting point of water is the temperature at which solid ice turns into liquid water.
• The freezing point of water is the temperature at which liquid water turns into solid ice.
• Both temperatures indicate the same state of matter.
• Hence, the melting and freezing points of water are the same, i.e., 0°C.

3. The boiling point of alcohol is 78°C. The temperature in the Kelvin scale is (B) 351 K.

• The conversion from Celsius to Kelvin is given as follows: K=C+273, where C is the temperature in Celsius, and K is the temperature in Kelvin.
• So, K = 78 + 273 = 351K
• Hence, 78°C is equivalent to 351K.

4. Latent heat of vaporization of water is 2.25×10⁶J/kg.

• Latent heat of vaporization is a physical property of a substance.
• It is defined as the heat required to change one mole of liquid at its boiling point under standard atmospheric pressure.
• It is expressed as kg/mol or kJ/kg.

5.  S.I. unit of temperature is (A) Kelvin.

• According to the International System, the S.I. unit of thermodynamic temperature is Kelvin.

6. In the sublimation process, (C) solid changes directly into gas.

• Sublimation is defined as a phase transition or change in the state of matter.
• In sublimation, a solid is directly converted into a gas without going through the liquid state.

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