1b- Elements, Compounds, Mixtures P2 Flashcards
What is simple distillation used for?
- To separate a liquid and soluble solid from a solution
OR - a pure liquid from a mixture of liquids
What does salt melt?
Ice
What is chromatography used for?
Separating and identifying unknown substances
What is the mobile phase in chromatography?
Water
What is the stationary phase in chromatography?
Paper
Why do the compounds in chromatography separate?
Each compound will be attracted to the two phases by different amounts
What does it mean if the compound has a strong affinity?
It will stick to the paper more
How can you identify a substance in chromatography?
By calculating the Rf value
How do you work out the Rf value?
Distance travelled by solute, divided by the distance travelled by solvent (water)
How big are Rf values meant to be?
1 or below. If over 1 than it’s wrong
What is a separating funnel used to separate?
Immiscible liquids
What s evaporation used to separate?
A solute from a solution
Why does evaporation work?
One substance has a lower boiling point than the other therefore separates by evaporating first.
What is filtration used to separate?
Insoluble Solids from liquids
Why do we grit roads in winter?
Sand creates friction
Salt melts ice
At what temperature do water and salt melt or freeze at?
Between -5° and -10°c
What are the steps to simple distillation?
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
How does fractional distillation work?
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
What is fractional distillation used to separate?
Two or more liquids that are miscible with one another
At what point in the column will substances with low boiling points condense during fractional distillation?
substances with the lowest boiling point will condense at the highest point in the column
At what point in the column will substances with high boiling points condense during fractional distillation?
substances with the highest boiling points will condense lowest point in the column
What does crystallisation separate?
A dissolved solid from a solution
