States of Matter and Mixtures Flashcards
Solid, Liquid and Gas
Melting and freezing take place at the melting point.
solid → liquid: melting
liquid → solid: freezing
Boiling and condensing take place at the boiling point
liquid → gas: boiling
gas → liquid: condensing
gas → solid: deposition
solid → gas: sublimation
What are physical changes?
State changes (melting, boiling, freezing and condensing) are physical changes – they involve the forces between the particles of the substances but the particles themselves don’t change.
What are chemical changes?
Chemical changes are where a new product has been formed.
Describe the term mixture
Consists of 2 or more elements or compounds not chemically combined together. Chemical properties of each substance in the mixture are unchanged.
Describe the term pure metal
A single element or compound, not mixed with any other substance.
How to distinguish between pure substances and mixtures on melting point data?
Pure substances melt and boil at specific/exact temperatures, mixtures do not.
What is simple distillation used for?
Used to separate a pure liquid from a mixture of liquids.
Works when the liquids have different boiling points.
Commonly used to separate ethanol from water. (Taking the example of ethanol…) ethanol has a lower boiling point than water so it evaporates first. The ethanol vapour is then cooled and condensed inside the condenser to form a pure liquid.
What are the sequences of simple distillation?
Sequence of events in distillation is as follows: heating -> evaporating -> cooling -> condensing.
How does fractional distillation work for hydrocarbons? (4)
1, The oil is heated in the fractionating column and the oil evaporates and condenses at several different temperatures.
2. The many hydrocarbons in crude oil can be separated into fractions each of which contains molecules with a similar number of carbon atoms.
3. The fractionating column works continuously, heated crude oil is piped in at the bottom. The vaporised oil rises up the column and the various fractions are constantly tapped off at the different levels where they condense.
4. The fractions can be processed to produce fuels and feedstock for the petrochemical industry.
What is filtration used for?
If you have produced e.g. a precipitate (which is an insoluble salt), you would want to separate the salt/precipitate from the salt solution. You would do this by filtering the solution, leaving behind the precipitate on the filter paper.
How does crystallisation work?
If you were to have produced a soluble salt and you wanted to separate this salt from the solution that it was dissolved in, you would first warm the solution in an open container, allowing the solvent to evaporate, leaving a saturated solution. Allow this solution to cool. The solid will come out of the solution and crystals will start to grow, these can then be collected and allowed to dry.
How does paper chromatography work?
Used to separate mixtures and give information to help identify substances. Involves a stationary phase and a mobile phase. Separation depends on the distribution of substances between the phases.
The more soluble a substance is, the further up the paper it travels.
How do you work out the Rf value?
Rf value = distance moved by substance / distance moved by solvent
Describe how waste and ground water can be made potable (3)
- Sedimentation: large insoluble particles will sink to the bottom of the water.
- Filtration: water is filtered through beds of sand which removes small insoluble particles.
- Chlorination: chlorine gas is put through water to kill microbes.
Describe how Sea water can be made Potable
Using distillation:
Filter the seawater, boil it and then water vapour is cooled and condensed.
