Chemistry: States Of Matter And Mixtures Flashcards
What are particles?
Molecules, ions or atoms
What are the three states of matter?
Solid, liquid and gas
What do we use to show different states?
A particle model
What is each perfume in a particle represented by?
A solid sphere
What do properties of each state of matter depend on?
The forces between the particles
What decides if the forces between particles are weak or strong?
Whether the substance is a solid, liquid or gas
Describe the structure (including forces) of solids.
Strain forces of attraction between particles hold them together in fixed positions in a regular lattice arrangement
What can we say about the movement of particles in a solid? What does this cause?
They hardly move at al, just vibrate about their fixed positions, so all solids keep a definite shape and volume
What can we say about the energy of particles in a solid?
They don’t have much energy
What happens to a solid (and particles in it) when it’s heated?
The hotter it becomes, the more the particles vibrate, causing solids to expand slightly when heated
Describe structure of liquids
Some force of attraction between the particles, they’re free to move past each other, but tend to stick together
What can we say about shape and volume of a liquid?
They don’t keep a definite shape and flow to fill the bottom of a container, but do keep the same volume
What can we say about comparison of the energy of particles between solids, liquids and gases?
Gases have more energy than liquids, which have more energy than solids
What can we say about movement of particles in a liquid.
Particles are constantly moving in a random motion. They will flow to fill the bottom of a container.
How does heat affect liquids (and its particles)?
Hotter the liquid gets, faster particles move. This causes liquid to expand slightly when heated
What can we say about the forces of gases, and their structures?
No force of attraction between particles, they’re free to move. They travel in straight lines and only interact when they collide.
What can we say of the shape and volume of gases?
Gases don’t keep a definite shape or volume and will always fill any container, and will escape if it’s not air-tight
What happens when gas particles bounce of the walls of a container?
They exert pressure on the walls.
What can we say about movement of particles in gases?
Particles move constantly with random motion. will always fill any container, and will escape if it’s not air-tight
How does heat affect gas (and its particles?)
The hotter gas gets, the faster the particles move. Gases either expand when heated, or their pressure increases,
What happens when you take away or add energy to a substance?
You can convert it from one physical state to another
Describe the three step process of a solid turning to a liquid
1) solid is heated, particles gain more energy
2) this makes particles vibrate more, weakening forces holding solid together. This makes solid expand
3) at a certain temperature, particles have enough energy to break free from positions. This is called melting.
Describe the three step process of a liquid turning to a gas
1) liquid heated, particles get more energy
2) energy makes particles move faster, weakening and breaking bonds holding liquid together
3) at a certain temperature particles have enough energy to break their bonds. This is called evaporating, and the liquid turns into gas
Solid turning straight to gas is called?
Subliming
During chemical reactions, what happens to atoms?
They are rearranged
When do chemical changes happen?
During chemical reactions, when bonds between atoms break and atoms change places
What is a chemical reaction?
Bonds between atoms break and the atoms change places. Atoms from substances you start off with (reactants) are rearranged to form different substances (products)
The table below gives Informatik about the Properties of four different substances, predict the state of substance D at 1000*C
Substance | melting point/*C | Boiling point/*C A | -218.4 | -183.0 B | 1535 | 2750 C | 1410 | 2355 D | 801 | 1413
1) the meltiNg point of D is 801C and it’s boiling point is 1413C
2) that means it’s a solid below 801C, a gas abode 1413C, and a liquid in between
3) 1000C is between 801C and 1413C, so D is a liquid at 1000C
What can we use data to work out in terms of sates of substances?
What state substances will be in under certain conditions
What is a pure substance?
A substance completely made up of a single element or compound
What’s a mixture?
More than one compound present, or different elements not all part of a single compound
You’ve got More than one compound present, or different elements not all part of a single compound. What is this?
A mixture
You’ve got a substance made up of a single element or compound - what is this?
A pur substance
What can we say about melting and boiling points in pure substances?
They are incredibly specific and sharp
How can we test for purity of a substance?
Compare actual melting point of a sample to the expected value
How do mixtures melt?
Gradually over a range of temperatures
What can we use to measure melting point of a substance? How does it work?
Melting point apparatus allows us to heat a small sample of a solid gehe slowly, so we can observe and record exact temperature it melts at
Adil’s teacher gives him samples of four powdered solids, labelled A, B, C and D. He used melting point apparatus to determine the melting point of each of the solids. Adil’s results are shown in the table below.
Solid | A | B | C | D Melting point (*C) | 82 | 72-79 | 101 | 63
Which of the four solids, A, B, C, or D, was a mixture?
B - Adil’s results show that solid B must be a mixture because it melted over a range of temperatures
What is simple distillation used to do?
To separate a liquid from a solution
Describe 5 steps of using simple distillation to get pure water from seawater
1) pour sample of seawater into distillation flask
2) connect bottom end of condenser to to a cold tap using rubber tubing, run cold water through condenser to keep cool
3) gradually heat distillation flask. Part of mixture with lowest boiling point (water here) will evaporate
4) water vapour passes to condenser where it cools + condenses. Flows to beaker, where it’s collected.
5) salt will be left in flask
Draw a diagram showing apparatus set up for simple distillation
Page 100 of GCSE combined science textbook
What is the problem with simple distillation?
Can only separate things with very different boiling points, won’t work with a mixture of different liquids with similar boiling points.
A liquid you’re heating in simple distillation is flammable, how do we heat it?
No Bunsen burner, use electric heater or water bath to heat it
What is fractional distillation used for?
Separating a mixture of liquids
Give Five steps of a lab demonstration used to model fractional distillation of crude oil at a refinery
1) put mixture in a flask. Attach fractionating column and condenser above flask
2) gradually heat flask. Different liquids will have different boiling points, will evaporate at different temps
3) liquid with lowest boiling point evaporates first. When temp on thermometer matches boiling point of this liquid, it has reached top of column
4) liquids with higher boiling temps may evaporate, but will condense in cooler area of column, running back down to flask
5) when first liquid has been collected, raise temperate until next one r aches the top
List equipment used in simple distillation of seawater to salt
Thermometer Flask Heating device (Bunsen burner) Condenser Tap Rubber piping Beaker Seawater
List equipment used in fractional distillation of crude oil
Bunsen burner Flask Crude oil substitute Fractionating column filled with glass rods Thermometer Condenser Test tubes
Draw diagram of set up of apparatus of fractional distillation
Page 100 of GCSE combined science book
What is filtration used for?
Separating an insoluble solid/solid impurities from a liquid reaction mixture
Describe the process of filtration
Put filter paper into a funnel and pour mixture into it. The liquid part of the mixture runs through paper, leaving behind the solid residue.
What is crystallisation used for?
Separating a soluble solid from a solution
Give the four steps of crystallisation?
1) pour solution into an evaporating dish and gently heat the solution. Some Agee will evaporate, so solution gets more concentrated
2) when crystals start to form (point of crystallisation ) remove dish from heat and leave to cool
3) salt should form crystals as it becomes insoluble in cold, highly concentrated solution
4) filter crystals out of solution, leave them to dry.
A mixture is composed of two substances, X and Y. Substance X is a liquid a room temperature, has a melting point of 5C and a boiling point of 60C. Substance Y is a solid at room temperature. It has a melting point of 745C and a boiling point of 1218C. Substance Y dissolves completely in substance X.
Suggest a purification method you could use to obtain a) A pure sample of substance X and b) A pure sample of substance Y
A) to her X on its own, you need to distil it from the solution. You can use simple distillation here as there’s only one liquid in the solution.
You could obtain a pure sample of substance X using simple distillation.
b) to get a soluble solid out of a solution, you should use crystallisation.
You could obtain a pure sample of substance Y using crystallisation
What is the purpose of chromatography?
Separating a mixture of soluble substances and identifying them
What are the two phases of chromatography?
A mobile phase and a stationary phase
In chromatography, what is the mobile phase?
Where molecules can move. This is always a liquid or gas.
In chromatography, what is the stationary phase?
Where molecules can’t move. This can be solid or a really thick liquid
As mobile phase moves of stationary phase in chromatography, what happens? Why?
Components in mixture separate out, they all end up in different places in stationary phase. This is because each of the chemicals in a mixture will pend different amounts of time dissolved in the mobile phase and stuck to the stationary phase.
What does how fast chemicAls move through the stationary phase ( in chromatography) depend on?
How it ‘distributes’ itself between the two phases
In paper chromatography, what is the stationary phase and what is the mobile phase?
Stationary = piece of filter paper
Mobile phase = solvent (e.g. Water, ethanol)
Give the 6 steps of paper chromatography
1) draw baseline near bottom of paper in pencil (pencil is Insoluble) put Spot of mixture to be separated on this line
2) Put some solvent into beaker. Dip bottom of paper (not spot!) in solvent
3) put watch glass on top of beaker to stop any solvent evaporating
4) solvent will move up paper. Chemicals in mixture dissolve in solvent, and move up paper too
5) different chemicals in the sample separate out, forming sports at different places on paper (an insoluble component won’t move from baseline)
6) remove paper from beaker before solvent reaches top. Mark distance solvent has moved (solvent front) in pencil
What two things does the amount of time the molecules spend in each phase ( in chromatography) depend on?
How soluble they Are in solvent
How attracted they are to stationary phase
In chromatography, a substance is insoluble in a solvent. What do you do to separate the components?
Rerun the experiment with same mixture with a different solvent
What can we say about how much time molecules with a higher solubility in the solvent) and which are less attracted to paper) will spend in each phase ( in chromatography) and what this means?
They’ll spend more time in mobile phase than stationary phase, so will be carried further up paper
In chromatography, where is the point of origin?
On the baseline
Why is chromatography useful?
Allows us to calculate Rf values for each chemical
What is the piece of paper you end up with in photography called?
Chromatogram
What do you do if you have chemicals in your mixture that are colourless? (In chromatography)
Spray chromatogram with a chemical called a locating Agent (shows where the spots are)
What is an Rf value?
The ratio between the distance travelled by the dissolved substance (solute) and the distance travelled by the solvent
What’s the formula for finding Rf values?
Rf = distance travelled by solute / distance travelled by solvent
How do you find the distance travelled by the solute, using the chromatogram
Measure from the baseline to the centre of the spot
How can chromatography be used to see if a certain substance is present in a mixture?
Run a pure sample (Standard Reference Material) of a substance that you think is in your mixture alongside a sample of the mixture itself. If it has the same Rf value as one of the spots, they’re likely the same.
What a pure samples ran for comparison in chromatography called?
Standard Reference Materials (SRMs)
How do we use chromatography to do a purity tesT?
Pure substance won’t be separated by chromatography - it’ll move as one blob, as opposed to multiple blobs of a mixture
Give the five steps of using a mixture of simple distillation and chromatography to analyse the composition of an ink
1) ink is a mixture of different dyes dissolved in solvent
2) to work out what solvent ink contains, do simple distillation. It allows you to evaporate off solvent and collect it - assuming solvent has lowest boiling point of everything in ink, it will evaporate first
3) thermometer will read boiling point of solvent while it’s evaporating. Use this boiling pour to determine what it is. E.g. 100*C = probably water
4) carry out paper chromatography on sample of ink - this will separate different dyes in ink, we can see how many there are
5) compare Rf values of different spots on chromatogram to reference values (or run further chromatography tests with pure substances) to work out what dyes are in ink
What do we call water that is fit to drink?
Potable water
What are the three places we can get water which can be purified?
Surface water: lakes, rivers, reservoirs
Ground water: from aquifers (rocks that trap water underground)
Waste water: contaminated by human process, can be treated
What does the treat-ability of water depend on?
How much purification is needed depends on the source. Ground water is usually quite pure, waste and surface water needs a lot of treatment
Give the three steps of water treatment process. Describe them.
1) filtration: a wire mesh screens out large twigs etc and then gravel and sand beds filter out any other solid bits
2) sedimentation: iron Sulfate or aluminium Sulfate is added to the water, which makes fine particles clump together and settle at the bottom.
3) chlorination: chlorine gas is bubbled through to kill harmful bacteria and other microbes
Why is distilling sea water not commonly used in the U.K.?
It requires lots of energy so is really expensive
When should you use deionised water?
For experiments that involve mixing or dissolving something in water
What is deionised water?
Wate that has had ions (such as calcium, iron and copper ions) present in normal tap water removed
Why do we not use normal water in experiments?
It can interfere with reactions and give us a false result
