questions (random, all!)

Question 1

what is a pure substance?

Answer 1

elements and compound

Question 2

what is an impure substance?

Answer 2

mixture

Question 3

what do impurities do to melting point and boiling point?

Answer 3

it lowers the melting point and raises the boiling point

Question 4

when do you use crystillization?
when do you use evaporation?

Answer 4

when the graph shows a curved line (solubility graph)

when the graph shows a straight line (solubility graph)

Question 5

what kind of substance can you NOT use evaporation till dryness for?

Answer 5

you use it on substances that dont decompose on heating.

Question 6

what is a “scenario” when you can use magnetic attraction to separate substances?

Answer 6

when one of the solids is magnetic and the other solid is not.

Question 7

what are two physical properties needed for the use of separating funnel?

Answer 7

the liquids have to be of different density and immiscible

Question 8

explain the process of crystallisation.

Answer 8

1. heat solution to saturation point.
2. cool the solution down to room temperature.
3. crystals will be formed :) :0

note: rapid cooling will lead to smaller crystals and slower cooling will lead to larger crystals

Question 9

how to calculate r.f. value?

Answer 9

it is the distance the dye/substance travelled/ distance the solvent travelled

Question 10

name THREE ways to separate two solids and name the physical property need for them to work

Answer 10

1. magnetic attraction
   ONLY ONE of the two solids have to be magnetic
2. sublimation (put a cotton wool to make sure gas does not escape)
   for solids who sublimate instead of melting, the temperature that the two solids sublimate at have to be different.
3. using a suitable solvent
   only one of the two solids should be soluble in the solvent.

Question 11

what is solubility?

Answer 11

it is the maximum mass of solute that can be dissolved in a fixed volume of solvent at a fixed temperature.

Question 12

what is a saturated solution?

Answer 12

a saturated solution is a solution that contains as much dissolved solute as it can at a given temperature and volume.

Question 13

what is the difference between suspension and suspension?

Answer 13

a solution is homogenous and a suspension is heterogenous. a solution is transparent but a suspension is cloudy. no solid particles can be seen in solutions but solid particles can be seen floating in suspensions