Separating Mixtures Year 9 Flashcards
What does pure mean?
Single element of compound not mixed with anything
What is the everyday meaning of pure?
Good or moral
What does impure mean?
Something containing more than 1 element
What is an element?
A substance made from only 1 type of atom
What is a melting point?
Temperature at which solid changes into a liquid
What is a boiling point?
Temperature at which liquid changes to a gas?
What is the difference in the melting and boiling points between pure and impure substances?
Pure substances have higher melting and boiling points
What is filtration?
A process used to separate an insoluble solid from a liquid
What does soluble mean?
Ability of a substance to dissolve
What are the steps for filtration?
Place mixture of solid and liquid in one beaker, and funnel with filter paper in the other. Pour mixture into funnel and observe as solid particles are caught by filter paper
Why is filtration successful?
Because filter paper has tiny holes called pores that allow dissolved particles to enter, but not undissolved particles(and therefore, the particles of the solid)
What is crystallisation?
Process used to produce solid crystals from a solution
What are the steps for crystallisation?
Place solution in an evaporating basin. Heat the basin with a Bunsen burner. Observe as water evaporates and only soluble particles are left behind
What is simple distillation?
Process used to separate a solvent from a solution
What are the steps for simple distillation?
Heat solution with Bunsen burner; salt will remain as it is while water will become water vapour. Connect flask of solution with condenser and place beaker under other end of condenser. Observe as vapour rises into condenser which cools it with cooling water, making it liquid again, before pure water drops into beaker
Why is simple distillation successful?
Because the dissolved water has a much higher boiling point than the solution it comes from
What is fractional distillation?
Process used to separate different liquids from a mixture of liquids
What are the steps for fractional distillation?
Heat conical flask of solution with Bunsen burner till liquids reach their boiling points, place a fractionating column in flask and connect column to a condenser which has one end over a beaker and put thermometer in column, observe as water vapour rises through column(which is hot at bottom and cooler at top) and liquids that condense drip back into flask while water vapour that reaches top of column enters condenser, before water vapour becomes liquid in condenser and falls into beaker
What is paper chromatography?
Process used to separate mixtures of soluble substances
What is paper chromatography often used on?
Food colourings, inks and plant pigments
What are the steps for paper chromatography?
Cut a piece of filter paper out(stationary phase), draw line with pencil on paper, place spots of mixture on line, dip paper in the solvent, observe as sample rises up paper and mark where it stops(mobile phase)
What is thin-layer chromatography?
Process used to separate mixtures of soluble substances
What are the steps for TLC chromatography?
Cut out piece of a TLC paper(stationary phase), add propane to the substance, draw line of piece of plate with pencil, use a thin capillary tube to add spots of mixture on line, add chromatography solvent into bottle with TLC plate, observe as solvent rises and mark where it stops
What is a chromatogram?
Result of separating mixtures by chromatography, used to identify substances by comparing them with known substances
What is the criteria that suggest substances are the same
If they have same number of spots(which must be matching in colour) or if the spots travel same distance as they have Rf value
What is the formula to calculate the Rf value
distance travelled by substance/distance travelled by solvent
What range must the Rf value be between
0-1
What is the substance not attracted to if its Rf value is 0?
Mobile phase
What is the substance not attracted to if its Rf value is 1?
Stationary phase
On a chromatogram, how many pigments does a pure substance have?
1
On a chromatogram, how many pigments does an impure substance have?
2 or more
