States of matter and mixtures

what are the 3 states of matter?

solid

liquid

gas

solid- arrangement of particles

regular pattern

solid- movement of particles

vibrate around a fixed position

solid- relative energy of particles

low energy

liquid- arrangement of particles

randomly arranged

liquid- movement of particles

move around each other

liquid- energy of particles

greater energy than solid

gas- arrangement of particles

randomly arranged

gas- movement of particles

move quicly in all directions

gas- energy of particles

highest energy

what type of change is a change in state?

physical change

what is the difference between a physical change and a chemical change?

physical change is reversible and doesn't change the chemical properties of the substance

unlike a chemical change

melting

solid to liquid

boiling

liquid to gas

freezing

liquid to solid

evaporation

liquid to gas

condensation

gas to liquid

sublimation

solid to gas

melting in terms of particles

heat energy increases particles' kinetic energy, allowing the particles to move

boiling in terms of particles

liquid particles gain so much kinetic energy that they escape

freezing in terms of particles

significant decrease in temperature= decrease in kinetic energy=particles lose so much energy that they become solid

evaporation in terms of particles

only occurs on the surface of liquids

where high energy particles can escape from the liquid's surface at low temperatures

condensation in terms of particles

When a gas is cooled its particles lose energy that when they bump into each other, they lack energy to bounce away again, instead grouping together to form a liquid

mixture definition

consists of 2 or more elements or compounds NOT chemically combined together

pure substance definition

a single element or compound, not mixed with any other substace

pure melting point data vs mixture melting point data

mixtures melt over a range of temperatures

whereas pure substances melt at specific/exact temperatures

this can be used to distinguish pure substances and mixtures

When should simple distillation be used?

used to separate a dissolved solvent from a solute (e.g. producing water from a salt solution)

Simple distillation works because the dissolved solute has a much higher boiling point than the solvent.

how to carry out simple distillation (trying to produce water from a salt solution)

1. The solution is heated, and pure water evaporates producing a vapour which rises through the neck of the round bottomed flask

2. The vapour passes through the condenser, where it cools and condenses, turning into the pure liquid that is collected in a beaker

3. After all the water is evaporated from the solution, only the solid solute will be left behind

when is fractional distillation used?

used to separate two or more liquids that are miscible with one another (e.g., ethanol and water from a mixture of the two)

how to carry out fractional distillation

1. The solution is heated to the temperature of the substance with the lowest boiling point

2. This substance will rise and evaporate first, and vapours will pass through a condenser, where they cool and condense, turning into a liquid that will be collected in a beaker

3. All of the substance is evaporated and collected, leaving behind the other components(s) of the mixture

when is filtration used?

Used to separate an insoluble solid from a mixture of the solid and a liquid

e.g. sand from a mixture of sand and water

how to carry out filtration

1. A piece of filter paper is placed in a filter funnel above a beaker

2. A mixture of insoluble solid and liquid is poured into the filter funnel

3. The filter paper will only allow the liquid to pass through as filtrate

4. Solid particles are too large to pass through the filter paper so will stay behind as a residue

when should crystallisation be used?

Used to separate a dissolved solid from a solution (e.g. salt and water)

how to carry out crystallisation

1. The solution is heated, allowing the solvent to evaporate, leaving a saturated solution behind

2. Cool the saturated solution

3. Crystals will begin to grow as solids

4. The crystals are collected by filtering the solution, they are washed with cold distilled water to remove impurities and are then allowed to dry

when should paper chromotography be used?

used to separate substances that have different solubilities in a given solvent

e.g. different coloured inks that have been mixed to make black ink

how to carry out paper chromotography

1. A pencil line is drawn on chromatography paper and spots of the sample are placed on it.

2. The paper is then lowered into the solvent container, making sure that the pencil line sits above the level of the solvent

3. The solvent travels up the paper, taking some of the coloured substances with it

4. Different substances have different solubilities so will travel at different rates, causing the substances to spread apart

why is a pencil line drawn on the chromatogram?

Pencil is used for this as ink would run into the chromatogram along with the samples

why should the pencil line be above the solvent?

so the samples don't wash into the solvent container

how to distinguish between pure and impure substances on a chromatogram

- Pure substances will produce only one spot on the chromatogram

- An impure substance therefore will produce a chromatogram with more than one spot

how to identify substances using Rf values

the same substance will have the same Rf value if dissolved in the same solvent

how to calculate the Rf value

(distance travelled by) SPOT / (distance travelled by) SOLVENT

how to identify substances by comparison with known substances

If two or more substances are the same, they will produce identical chromatograms

stationary phase

the paper

mobile phase

the solvent running through the paper

potable water

potable water: it is suitable for drinking so must have:

- low levels of microbes

- low levels of contaminating substances

NOT the same as pure water

what are the 3 steps to make waste and ground water potable

1. sedimentation

2. filtration

3. chlorination

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

how to make sea water potable

distillation

distillation when making seawater potable

1. filter the seawater

2. boil it

3. water vapour is cooled and condensed

why must water used in anaylsis be pure?

must be pure because any dissolved salts could react with the substances you are analysing, leaving you with a false result