1b- Elements, Compounds, Mixtures P2

Question 1

What is simple distillation used for?

Answer 1

• To separate a liquid and soluble solid from a solution
  OR
• a pure liquid from a mixture of liquids

Question 2

What does salt melt?

Answer 2

Ice

Question 3

What is chromatography used for?

Answer 3

Separating and identifying unknown substances

Question 4

What is the mobile phase in chromatography?

Answer 4

Water

Question 5

What is the stationary phase in chromatography?

Answer 5

Paper

Question 6

Why do the compounds in chromatography separate?

Answer 6

Each compound will be attracted to the two phases by different amounts

Question 7

What does it mean if the compound has a strong affinity?

Answer 7

It will stick to the paper more

Question 8

How can you identify a substance in chromatography?

Answer 8

By calculating the Rf value

Question 9

How do you work out the Rf value?

Answer 9

Distance travelled by solute, divided by the distance travelled by solvent (water)

Question 10

How big are Rf values meant to be?

Answer 10

1 or below. If over 1 than it’s wrong

Question 11

What is a separating funnel used to separate?

Answer 11

Immiscible liquids

Question 12

What s evaporation used to separate?

Answer 12

A solute from a solution

Question 13

Why does evaporation work?

Answer 13

One substance has a lower boiling point than the other therefore separates by evaporating first.

Question 14

What is filtration used to separate?

Answer 14

Insoluble Solids from liquids

Question 15

Why do we grit roads in winter?

Answer 15

Sand creates friction

Salt melts ice

Question 16

At what temperature do water and salt melt or freeze at?

Answer 16

Between -5° and -10°c

Question 17

What are the steps to simple distillation?

Answer 17

1) solution is heated
2) the part of the solution with the lowest boiling point evaporates first.
3) the vapour is cooled and the condensed liquid is collected

Question 18

How does fractional distillation work?

Answer 18

The crude oil is heated
The oil evaporates
The vapours move up the fractioning tower and the temperature fall
Different vapours condense at different heights in the tower
In this way crude oil is separated into fractions
Each fraction contains hydrocarbons of similar sized molecules

Question 19

What is fractional distillation used to separate?

Answer 19

Two or more liquids that are miscible with one another

Question 20

At what point in the column will substances with low boiling points condense during fractional distillation?

Answer 20

substances with the lowest boiling point will condense at the highest point in the column

Question 21

At what point in the column will substances with high boiling points condense during fractional distillation?

Answer 21

substances with the highest boiling points will condense lowest point in the column

Question 22

What does crystallisation separate?

Answer 22

A dissolved solid from a solution