Lab 4

Question 1

Which of these properties is determined without changing the identity of the substance, physical or chemical properties?

Answer 1

Physical properties
In chemical properties, the compounds change their composition

Question 2

Difference between intensive and extensive physical properties

Answer 2

Intensive
Properties that are not affected by the amount of matter
Ex: colour, m.p, b.p, density

Extensive
Properties that are affected by the amount of matter
Ex: mass, volume, length, shape

Question 3

Physical properties

Answer 3

The property of a pure compound that helps in its identification.

Question 4

A compound can have different Physical Properties like:

Answer 4

Colour (S,L)
Melting Point (S)
Sublimation (S)
Boiling Point (L)
Freezing Point (L)
Refractive Index (L)
Density (L)
Odour (S,L)
Hardness (S)
Solubility (S,L)

Question 5

Melting point

Answer 5

It is the temperature at which a solid compound changes state from solid to liquid at 1 atmospheric pressure.
At the melting point, the solid and liquid phase exists in equilibrium.

Question 6

Melting point range

Answer 6

The difference between the temperature at which the collapse of solid crystals is first observed and the temperature at which the solid sample becomes completely liquid.
It should not exceed more than 1°C.

Question 7

Difference between pure and impure/ crude compounds

Answer 7

Pure compounds - melts over a narrow range
Impure/ crude compounds - melts over a widerange

Question 8

Boiling point

Answer 8

The boiling point of the liquid is the temperature at which the pressure of the vapour is equal to the atmospheric pressure (1 atm. pressure or 760 mm Hg).

Question 9

Relation between the boiling point (temp.) and the pressure

Answer 9

Directly proportional
a liquid will boil at a higher temperature when the external pressure is higher and will boil at a lower temperature when the external pressure is reduced.

Question 10

B.P. of Water
B.P. of Ethanol
B.P. of Diethyl ether

Answer 10

B.P. of Water = 100°C
B.P. of Ethanol = 78.5°C
B.P. of Diethyl ether = 34.6°C

Question 11

Change of energy forms at the boiling point

Answer 11

From heat energy to kinetic energy

Question 12

Effect of Vapour pressure on Boiling point

Answer 12

Boiling point of a liquid is directly proportional to vapor pressure.

Question 13

Sublimation

Answer 13

a process that involves the direct conversion of a solid to a gas without passing through the liquid state.

Question 14

Melting point apparatus

Answer 14

Analogue

Question 15

Function of the boiling chips

Answer 15

Prevent excess boiling