IX Practical Chemistry KBSE Experiment No. 3

To find out the melting point of Candle Wax and Boiling point of Benzene or Ethyl Alcohal.

Viva Voce
Q.1. What do you understand by by Boiling?

Ans. Boiling is defined as the state at which the liquid starts changing into vapour at fixed temperature.

OR

Boiling is the state of liquid at which the vapour pressure of the liquid becomes equal to atmospheric temperature.


Q.2. What is Boiling Point?

Ans. That fixed temperature at which the liquid starts boiling is known as Boiling Point.


Q.3. What do you understand by "Melting"?

Ans. That state of solid at which it starts changing into liquid without change of temperature is called Melting.

Q.4. What is melting point?

Ans. The fixed temperate at which a solid melts or changes into liquid is called Melting Point.


Q.5. Is Benzene or Ethyl Alcohal an Inorganic Compount?

Ans. No! It is an Organic Compound.


Q.6. What is the formula of Benzene or Ethyl Alcohal?

Ans. The formula of Benzene is C6H6 and formula of Ethyl Alcohal is C2H5OH.


Q.7. Is wax an Inorganic Compound?

Ans. No! The wax is an Organic Compound.


Q.8. What is the effect of pressure on melting point?

Ans. The melting point of that substance which expands on freezing decreases with pressure i.e. its melts at lower temperature.


Q.9. What is the effect of pressure on melting point in case of those substances which contract on freezing?

Ans. By increasing the pressure the melting point of those substances which contract on freezing is increased.


Q.10. What do you understand by Evaporation?

Ans. The change of liquid into vapour at all the temperature is called Evaporation.


Q.11. Is Benzene an element or a compound?

Ans. Benzene is a compound.


Q.12. Which elements are present in Benzene?

Ans. Carbon and Hydrogen are present in Benzene.


Q.13. What is the effect of pressure on boiling point?

Ans. If the pressure is increased then the boiling point increases.


Q.14. What is the effect on melting point of Wax if pressure is increased?

Ans. The Melting point of wax rises with increase of pressure because wax contracts on freezing.


Q.15. What are the factors on which rate of evaporation depends?

Ans. Rate of evaporation depends upon the following factors.

1. Nature of liquids

2. Area of Surface

3. Temperature of Liquid

4. Temperature of Air

5. Dryness of Air

6. Motion of Air

7. Pressure


Q.16. What is the Latent Heat of Fusion of Ice?

Ans. Amount of Heat taken by 1 Kg of Ice at its melting point in changing into water at the same temperature is called Latent Heat of Fusion of Ice.


Q.17. Why does temperature remain constant at boiling point of liquid?

Ans. At this stage the heat is utilized for converting liquid into vapours so the temperature remains constant.


Q.18. What is the boiling point of pure water?

Ans. The boiling point pure water is 100oC at a pressure of 760 m.m.


Q.19 Does the boiling point of liquid depend upon the pressure of atmosphere?

Ans. Yes! The boiling point of liquid depends upon atmospheric pressure.


Q.20. What is the difference between Boiling and Evaporation?

Ans. Boiling Boiling is a rapid change of liquid into vapour and takes place at definite temperature. Moreover the boiling takes place throughout the mass of liquid.

Evaporation Slow change of liquid into vapour at all the temperatures is called Evaporation. It takes place at the surface of liquid.


Q.21. What is effect of height on the boiling point of liquid?

Ans. With increase of height the boiling point of liquid decreases.


Q.22. Why should we stir the liquid during the process of heating?

Ans. The liquid should be stirred constantly for helping the liquid in maintaining uniform temperature.

Q.23. What precautions should be taken in determination of melting point of wax?

Ans. The following precautions should be taken in determination of melting point of wax.

1. The Capillary tube should be so long that its upper part should be out of beaker.

2. The bath should b heated slowly with constant stirring.

3. Reading of Thermometer should be taken when steady stream of bubble starts to appear.