2. States of Matter and Mixtures Flashcards
What are the three states of matter?
Solids, liquids, and gases
Solid —> liquid
Melting
Liquid —> solid
Freezing
Liquid —> gas
Boiling / evaporating
Gas —> liquid
Condensing
Gas —> solid
Deposition
Solid —> gas
Sublimation
Characteristics of solids
- Particles very close together.
- Fixed shape and volume.
- Particles vibrate in a fixed position.
- Particles have less energy than liquids or gases.
Characteristics of liquids
- Particles very close together.
- Fixed volume but can change shape and fill a container.
- Particles move and flow randomly past one another.
- Particles have less energy than gases but more than solids.
Characteristics of gases
- Particles are far apart.
- Can change shape and volume to fill any container.
- Particles move randomly in all directions.
- Particles have more energy than solids and liquids.
What does strong forces between particles mean?
- More energy is required to overcome these forces.
- High melting and boiling points.
What does weak forces between particles mean?
- Less energy is required to overcome these forces.
- Low melting and boiling points.
Define mixture
- Consists of two or more elements or compounds not chemically combined together.
- Can be separated.
- Chemical properties of each substance in the mixture are unchanged.
What is a pure substance in chemistry?
A single element or compound, not mixed with any other substance.
TRUE OR FALSE: Pure substances melt and boil at specific/exact temperatures, mixtures do not due to consisting of 2 or more elements or compounds.
True
Explain simple distillation
Used to separate a pure liquid from a mixture of liquids with different boiling points. The liquid with lowest boiling point evaporates first. The vapour released passes through a condenser where is cools and condenses to form a pure liquid.
Explain fractional distillation
- The many hydrocarbons in crude oil can be separated into fractions each of which contains molecules with a similar number of carbon atoms.
- 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.
- The fractions can be processed to produce fuels and feedstock for the petrochemical industry.
Explain filtration
Separates mixtures of insoluble solids and liquids. Done by pouring the mixture through filter paper.
- The insoluble solid is trapped and left behind on the filter paper.
- The liquid runs through the filter paper and is collected below.
Explain crystallisaton
Separates solutions into their constituent (different) parts: dissolved solids (solutes) and liquids (solvents).
- Heat the solution in an evaporating basin, e.g. with a Bunsen burner, so that the solvent evaporates.
- Eventually, crystals of the solute will form.
- We can collect the solvent by condensing it as it evaporates.
Explain paper chromatography
Separates solutions with a number of different solutes (solids) in the solvent (liquid) - usually separating different coloured pigments (ink).
- Place a drop of the solution to be separated near the bottom of a piece of chromatography paper.
- Dip the very bottom of the paper into a suitable solvent.
- The solvent moves up the paper and carries the solutes in the solution with it.
- Different solutes move at different speeds, so they separate on the paper. The more soluble the substance is, the further up the paper it travels.
What should pure substances show on a paper chromatogram?
Should only have one spot on the chromatogram.
What should impure substances/mixtures show on a paper chromatogram?
Will show up with more than one spot on a chromatogram.
How do you calculate Rf value in paper chromatography?
Distance moved by substance / distance moved by solvent
Potable water
It is suitable for drinking so it must have:
- Low levels of microbes.
- Low levels of contaminating substances.
- It is not the same as pure water but is still safe.
How can waste and ground water be made potable?
1) Sedimentation: large insoluble particles will sink to the bottom of the water.
2) Filtration: water is filtered through beds of sand which removes small insoluble particles.
3) Chlorination: chlorine gas is put through water to kill microbes.
How can sea water be made potable by using distillation?
1) Filter the seawater.
2) Boil it.
3) Water vapour is cooled and condensed.
Why does water need to be pure in analysis?
Because any dissolved salts could react with the substances you are analysing, leaving you with a false result.
Mobile phase in chromatography
Liquid or gas
Stationary phase in chromatography
Solid or viscous liquid
TRUE OR FALSE: In chromatography, substances are picked up and carried by a mobile phase, which then moves through a stationary phase.
True
