unit 1B Pure substance

Question 1

what is pure substance made of ?

Answer 1

• only one type of elements or only one type of compounds,
• only one type of atoms or only one type of molecules

Question 2

what is the melting point for pure water?

Answer 2

zero degress cesius ( 273 kelvins)

Question 3

what is a boiling point for pure water?

Answer 3

one hundred degrees celsius ( or 373 kelvins)

Question 4

what is simple distillation for?

Answer 4

to get a liquid from a souble solid in a liquid

Question 5

what is a anti-bumping granules ?

Answer 5

small pieces of quartz to make the boiling smoother

Question 6

what is a liebig condeser?

Answer 6

This is to ensure that the condenser is completely filled.

Question 7

why does simple distillation works?

Answer 7

• the dissolved solid has a much higher boiling point than the solvent.

Question 8

what happens when the solution is heated?

Answer 8

• solvent vapour evaporates from the solution example salt water

Question 9

what is fractional distillation?

Answer 9

To separate a mixture of miscible liquids

Question 10

why does fractional distillation works?

Answer 10

• the different liquids have different boiling points.
• The substance with the lowest boiling point is collected first.

for example: To separate ethanol from a mixture of ethanol and water.

Question 11

what is filtration?

Answer 11

to separate an insoluble solid suspended in a liquid

Question 12

why does filtration works

Answer 12

• the filter paper has tiny holes in it.
• These are large enough to let anything dissolved in the liquid through but not the much larger particles of undissolved solid

to separate salt from rock salt

Question 13

what is crystallisation?

Answer 13

to get a solid from a soluble solid in a liquid

how to obtain pure dry crystals from a salt solution