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Chemistry > c1 - atomic structure > Flashcards

c1 - atomic structure Flashcards

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1
Q

What does the periodic table show ?

A

-The periodic table shows us all the elements .
-There are over 100 elments .

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2
Q

What is an element ?

A

A substance made up of only one type of aotm .

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3
Q

What are compounds ?

A

Compounds contain two or more different elemnts chemically bonded .
-Combined in a fixed proportion .

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4
Q

Key fact about compounds .

A

Compounds usually have totally different properties from the elemts that theya re made from .
-If we want to separate a compound , back into its elemnts , we need to use a chemical reaction .

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5
Q

What is a mixure ?

A

We have different elemnnts or compounds which are not chemically combined togther
-If we want to sepearate a mixture , then we use physical techiniques rather than chemcil rections .

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6
Q

What is a molecule ?

A

A molecule has anyy elemnts chemically joined .

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7
Q

What does a chemical formula show ?

A

Tells us all the elents in a molecule and also the number of atoms in each eement .
-you cannot change the small number in a chemical formula as this producs a different molecule .

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8
Q

What is the law of conservation of mass ?

A

The total number of products formed in a reaction is equal to the total number of reactants .

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9
Q

Physical separations can be used to separate ?

A

Mixtures , but cannot be used for elements in a compound .

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10
Q

Gieva few examples of Physical separation techniques :

A

-Filitriation
Crystalisation .
-Distillation
-Chromatoraphy

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11
Q

When is fitiration used ?

A

Filtriation is used to separate an insoluble soild from a liquid .
(insoluble means solid won’t dissove in a liquid ) .

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12
Q

Conditions for filitration .

A

Solid and LIquid (check state symbolds)
-Need a filter funnel and filter paper .

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13
Q

Stage one of filitiration .

A

Pour mizure into filter paper .
-The liquid passes through the tiny pores in filter paper . (fitrate)

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14
Q

Stage two of filtiration .

A

HOwever solid material can’t pass through the filter paper and so is trapped . (residue)
-In the end liquid is separated form the soild .

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15
Q

When is crystalisation used ?

A

Used to separae a soluble solid from a liquid . Aqueous solution need (aq) check state symbols .

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16
Q

What is one way of doing crystalisation ?

A

-Leave the solution for a few days and water will evaporate leaving crystals of ur thing sodium chloride eg .

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17
Q

What to do if you want crysalisation to happen faster ?

A

-Heat the solution to evaportae out water .
-Bbe careful that the chemical we are trying to crystalise is not effected by the heating . Certain chemcials break down when heated .

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18
Q

What is simple distillation ?

A

Used to separate a liquid from a solid if we want to keep the liquid .

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19
Q

How does simple distialltion work ?

A

First we evaporate the liquid by heating ,
-We then condense the vapour by cooling

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20
Q

How does simple distillaiotn work ?

A

-Heat the solution
-vapour now rises up glass tube
-vapour now passes into the condeser (kept cold as cold water circulates the condseer ).

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21
Q

How does simple distillaton work (2) ?

A

-This mens vapour condenses turning vapour into a liquid .
-collect liquid in a beaker , Left with crystals of solid in a flask and liquid in a beaker .

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22
Q

What happens in fractional distilaiton ?

A

We sepeare a mixture of different liquids .
KEY POINT - these liquids must have different boiling points .

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23
Q

first stage of fractional distillation ?

A

1.Start by gently heaitng the mixtures .

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24
Q

second stage of fractional distillation ?

A

the liquids start to evaporate , But one with lower boiling point will evaporate more easily .

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25
Q

third stage of fractional distillation ?

A

When the vapours hit the fractonationg column , they condense and drip back into the falsk . The lquids hthen evaporate agaon .

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26
Q

fourth stage of fractional distillation ?

A

The repeated evaporation and cndensation increasing the amount of lower boiling point chemical in the fractonaitng column .

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27
Q

fifth stage of fractional distillation ?

A

As warm vapours pass up the coluumn they reach the thermoemter and temperature of it begins to rise .
-meaning a mixture of 2 different vapours are passing over the thermomeer .

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28
Q

sixth stage of fractional distillation ?

A

both vapours now pss into condenser and turn into a liquid .
-comes a point where temperature on thermoemter reaches bioling point of first chemical and it stops rising .

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29
Q

seventh stage of fractional distillation ?

A

now only one chemical in the condenser , so this is collected in a beaker .

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30
Q

eighth stage of fractional distillaiton

A

then the temperture rises agaom until reaches boiling point of second chemical , colect this in a second beaker .

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31
Q

What is the porblem if the liquids have very similar points in fractional distillation ?

A

-much harder to sepearte the liquids , might need multiple rounds of fractional distillaition .

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32
Q

fractional distillaiton to purifhy large volumes of lquid ?

A

-Sme principle but also requires different equipment . .

33
Q

dra and label simple and fractional distillaiton .

A

check sheet .

34
Q

How does paper chromatogrpahy do ?

A

Allows us to separate substances based on their dffierent solubilities .

35
Q

first stage of papepr chromatogrpahy .

A

take a piece of chromatography paper .
-draw a pencil lne near th botom .

36
Q

second stage of paper chromatogrpahy .

A

-put dots of our colours (substance) on a pencil line .

37
Q

third stage of paper chromatogrpahy .

A

now put paper into solvent
(a liquid that will dissolve substances ).

38
Q

fourth stage of paper chromatogrpahy .

A

The solvent now makes it way up the paper and dissolves the ink and coloured dots , which are also carried by the paper .

39
Q

Why is paper in chromatography called stationary phase and the solven called mobile phase ?

A

Paper called stationary pahse as it does not move .
SOlvent called mobile pahse as it moves .

40
Q

A pure compound …

A

will produce a sinlge spot in all solvent ,

41
Q

a compound in a mixture (mixture of colours )

A

may sepearate into a different spots depending on the solvent .

42
Q

More soluble substances…

A

travel further up the paper .

43
Q

Why do we draw the starting line un pencil ?

A

As if we draw the line in pen , the pen ink would also move up with the solvent effecting the results

44
Q

How to figure out unknown substance using chromatogrpahy .

A

-normal process of chromtogrpahy ,
measure the distance mvoed by the unkwon chemical (distance from pencil line to center of dot.)
-Measure the distancce moved by solvent .
Calcualtre rf calue distance moved by substance / distanced moved by solvent .
no untis .
look up in data base to find substance ,.

45
Q

Rf value facts .

A

Several substacnes may have the same Rf calue , some may need to be repeated using a diffeent solvent .
If a substance has never been analysed before m ti willl have no rf value .

46
Q

RQP for paper chromatogrpahy .

A

Sample of food chemicals ,
4 known food coloruings (a -d)

47
Q

First stage pf paper chromatogrpahy rp ?

A

draw a hroizontal pencil line 2cm from the bootm of paper .

48
Q

Second stage of paper chromatogrpahy rp ?

A

Mark five pencils pots at equal spaces acroos line .
-make sure there 1cm clear on each side of the paper .

49
Q

Third stage of paper chromatogrpahy rp ?

A

use a capiallary tube to put a small spot of eak of the known colours and the unkown colours ontol pencil spot

50
Q

fourth stage of paper chromatogrpahy rp ?

A

now pour waer into beaker depth of 1cm water in this case solven .

51
Q

fifthstage of paper chromatogrpahy rp ?

A

attach a glass rod using tape and lower paper into a glass beaker ,bottom of paper should dip into water .

52
Q

pencil line with psots must be above the surface of water why ?

A

or water will wash off the line .

53
Q

the sides of the paper must not touch side walls why >

A

or it will interfere with the way water move s.
-Put a lid on beaker , to reudce the amount of evaporation of he solven t .

54
Q

sixth stage of paper chromatogrpahy rp ?

A

at this stage water moeves up paper and colours are carried with it
remove paper when water travleld three quarters up it ,
-use a pencil to mark point how far water reached , Hang paper to dry .

55
Q

where are the unkwon colours ..

A

the spots that line up with the unkwon colour is unkown colour .

56
Q

what did greeks say atoms were ?

A

Atoms were tiny spheres that cannot be divided .

57
Q

What happned in 1897 ?

A

Scientists discovered atoms contain tiny negative elexrons called electrons ,
-showed that atoms have an internal structure .
Came to the invention of plum puddign model - ball of possitive charge with embedded negative elctrons .

58
Q

What did scientists do to see i the plum pudding model was correct ?

A

Did the alpha scateeirng experiment .

59
Q

What happened in the alpha scattering experimen t .

A

-scientits took a piece of gold foil , gold used as it can be hammered into very thing foil .
-Then fire tiny positive alpha particles athe goild foil .

60
Q

What was the first observation of alpha scattering model .?

A

-most atoms passed striaght thorugh gold foil without changing idrection .
-meant atoms were mostly empty space . .

61
Q

What was the second observation of the alpha scattering model ?

A

-some alpha particles were deflced , changed direction when passin thorugh the gold foil ,
-meant the center of the atom must have a positive chtge , particles that came close to his are reppelled and changed direction .

62
Q

what was the third observtion of the aplha scatering model ?

A

-some alpha particles bounced striaght off gold oil ,
-meant center of atom mst have a great deal of mass , center called nucleus ,

63
Q

what did scienits do when they found reuslt of alpha scattering model ?

A

scientists replaced with nuclear model .
-empt space
-tiny positve nucleus
-around the egde , negative electrons .

64
Q

What did Niels Bohr propose ?

A

He proposed electorns orbit the nucleus at specific distacnes , which was accepted by scienits .
-now call thse “orbits” energy levels /shells .

65
Q

what happened several years after niels bohr .

A

-posiitve charge in nuclues so tiny positive particles called protons .
20 years after James CHadwick said nucles also contains neutrols .
soa toms have no overal chatge as number of protons is euqaal to number of electrons .

66
Q

What is the radius of an atom.

A

1*power of minus ten .

67
Q

what is the radius of a nuclues

A

1*ten to power of -14 .

68
Q

stae relative mass and relatve charge of proton neutrol and electron .

A

check sheet .

69
Q

What is the mass number ?

A

number of protons +neurons .

70
Q

What is the atomic number ?

A

NUmber of portons which is equal to the number of electrons .

71
Q

How do you work out the number of neutrons ?

A

Mass number - atomic number .

72
Q

What are isotopes ?

A

-Isotopes are atoms of the same element with different number of neutrons .
-All atoms of an elemn have the same number of protons .

73
Q

What are ions ?

A

Ions are atoms which have gained an overrall charge .
They have gained or lost electrons .

74
Q

More about ions ?

A

Positiove ions have lost electrons .
Negative ions have gained electrons
(check sheet for an example ).

75
Q

electrons exist in …

A

energy levels .
-each energy level holds a maximum number of electors .

76
Q

1 st sheel holds two electrons
what does the second and third shell hold
what does the fourth shell hold ?

A

electrons .8 electrons
18

77
Q

How do you work out wat group an elet is in by looking at the elctronic structure ?

A

the last number , if it is (2,6) last number shows it is in group 6 .

78
Q

elements with full outer energy levels are found in …

A

group 0 , noble gases .

Chemistry (20 decks)

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