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GCSE Chemistry OCR A > C2 > Flashcards

C2 Flashcards

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1
Q

What is relative atomic mass?

A

🔮The mean mass of an atom of an element compared to 1/12 the mass of a carbon -12 atom
💎 the bigger number on the periodic table

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2
Q

What is the relative formula mass ?

A

The sum of the relative atomic masses of the atoms in the number of the shown formula.
“The weighted mean mass of the formula of units compared to 1/12th of the mass of a carbon 12 atom”
(For substances that consist of two or more atoms)

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3
Q

What is an empirical formula?

A

The simplest whole number ratio

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4
Q

What is the difference between molecular formula and displayed formula?

A
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5
Q

What is a compound?

A

Eg: water
Like a combination of molecules
composed of 2 or more separate elements

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6
Q

What does it mean for a substance to be ‘pure’ ?

A

To only have one element or compound

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7
Q

What does it mean to have an ‘impure’ substance?

A

A substance that contains more than one element or compound

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8
Q

Why are useful materials mixtures?

A

Pure materials are too soft for everyday use, therefore alloys are used

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9
Q

How would you know whether a substance impure or impure from the BP/MP?

A

Pure substances melt /boil at a specific temperature
🚬if impure then the different substances will melt over a range of temperatures, and will be less than pure substance MP

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10
Q

What does filtration separate?

A

An insoluble solid from a liquid.
Liquid = filtrate
Solid = residue

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11
Q

What is crystallisation used for, and how is it conducted?

A

Separating a soluble solid from a solution.
💎evaporate solvent in an evaporating dish
💎leaves a saturated solution
💎after cooling becomes crystals
💎 dry in warm oven or by patting with filter paper(air drying)

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12
Q

How does simple distillation work?

A

Separates a liquid from a solution (solute),
Can only be used to separate things with very different boiling points
1. Substance evaporates
2. Vapour travels to water jacket and condenses

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13
Q

How does fractional distillation work?

A

Separates a liquid from a mixture of liquids
1. Liquid with lowest boiling point goes first putting it at the top of the column.
2. Others condense back down due to the factional column
Follows normal distillation

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14
Q

Describe the fractioning column

A

Lots of little glass rods (high surface area)
Tall which means colder at the top

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15
Q

What is a mobile phase?

A

The molecules can move
Liquid or gas

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16
Q

What is a stationary phase?

A

Where molecules cannot move
Always solid

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17
Q

How does paper chromatography work?

A

MP= water
SP= paper
Use a pencil (insoluble)
Make sure paper is in water but not touching the dots

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18
Q

How does thin layer chromatography work?
+ safety points

A

A glass /plastic plate
SP= silica or alumina powder
MP= solvent
Draw a line in pencil

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19
Q

How do you calculate the retention factor?

A

Distance travelled by substance ➗distance travelled by solvent
* will always be less than 1

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20
Q

How does gas chromatography work?

A

MP= inert carrier gas eg:
SP = silica or alumina powder packed into metal columns
Gas is put into column and how long it takes to come out dependent on how attracted it is =retention time

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21
Q

What are some advantages of thin layer chromatography?

A

🔴it’s quicker
🔴it’s more sensitive , so less can be used
🔴 larger range of stationary phases/ solvents to choose from

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22
Q

How do you read a gas chromatogram?

A

Pure substance = one peak
The more time taken = least attracted to mobile phase

The area under each peak is how much there was of each substance

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23
Q

What are the typical properties of metals?

A

🪙shiny
🪙high melting and boiling point
🪙solid at room temperature
🪙malleable
🪙ductile
🪙good conductors
🪙found on the left of the periodic table
🪙lose electrons to form positive ions

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24
Q

What are typical properties of non-metals?

A

🪙dull
🪙low MP/ BP
🪙brittle
🪙insulators
🪙gases/ liquids
🪙found to right on periodic table
🪙gain electrons to become negative ions

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25
Q

What does malleable mean?

A

It bends without shattering

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26
Q

What does brittle mean

A

Shatters when hammered
*particles can not easily change their position in the lattice structure

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27
Q

What happens when metals and non metals oxides dissolve in water?

A

Metal oxides = alkaline solutions
Sodium oxide (alkaline)

Non - metal oxides = acidic solutions
Carbon dioxide (acidic)

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28
Q

What is the dividing gap on the periodic table?

A

Step ladder from B to At become non -metals

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29
Q

How is the periodic table arranged

A

Ascending atomic weight
Groups = ⬇️ all react similarly and have same properties (last number on configuration)
Periods =⬅️ how many shells the element has

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30
Q

How do you calculate electric configuration?

A

The atomic number
Max config is 2.8.8.18

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31
Q

How are ions formed ?

A

When an atom loses or gains electrons

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32
Q

typical rules of Dot and cross diagrams

A

❌ square brackets must have charge of ion on them
⚫️ draw all shells to be in the safe side

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33
Q

Describe the bonding ionic compounds :

A

🔳 ionic bonding
🔳formed between a metal + non metal
🔳 dot and cross diagrams
🔳held together by string electrostatic forces of attraction between oppositely charged ions

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34
Q

Describe ionic compounds structure and bonding :

A

Giant ionic lattices :
In solid state contain positive and negative ions arranged regularly

Strong Mp/Bp
When melted or dissolved in water can conduct electricity (IONs move and carry the current)

35
Q

What are some limitations of the ball and stick model?

A

Not to scale - shows large gaps between the ions
Doesn’t show charge
Doesn’t show chemical symbols

36
Q

What are some limitations of the space filling model?

A

Only shows the outer layer of the compound

37
Q

What is a limitation if the dot and cross model?

A

Doesn’t show the 3D size

38
Q

Describe covalent bonding

A

🟢Sharing electrons
🟢Between non metals
🟢Electrostatic attraction between positive nucleus and shared electrons

39
Q

Describe simple molecules

A

Strong covalent bonds between atoms but weak intermolecular forces between molecules
Low Mp/Bp
Do not conduct electricity

40
Q

Describe giant covalent structures :

A

Normally Do not conduct electricity
High Mp/Bp because the whole thing is strong covalent bonds
Many non metal atoms joined by covalent bonds and arranged in a repeating regular pattern called a giant lattice (giant covalent lattices)

41
Q

Describe diamond’s structure and Bonding

A

Where all four electrons are shared in carbon
Very high Mp/Bp
Giant covalent structure
hard
Cannot conduct electricity as all four electrons are bonded
repeating structure (tetrahedral network)

42
Q

Describe graphite’s structure and bonding :

A

Giant covalent structure
Each carbon atom is covalently bonded to three other carbon atoms
Both can conduct electricity (1 electron in outer shell becomes delocalised)
Layered structure
High Mp/Bp
Graphite has very weak forces between the hexagonal layers allowing it to slide over each other (slippery)

43
Q

What are fullerenes ?

A

Large carbon molecules
Used as lubricants
Hollow
Moves over each other easily - slippery

44
Q

Describe the size of nano particles

A

Between 1nm and 100nm across
A few hundred atoms

45
Q

What are some uses for nano particles?

A

Large SA:V ratio
Catalyst
Medicine
Electrical circuits- can conduct electricity

46
Q

What are some issues with nano particles?

A

Could harm the environment
Could damage cells

47
Q

How do you draw polymers

A

Made up from monomers
Written in bracket with n
Curved brackets with bonds coming through

48
Q

What are polymers

A

Covalent bonds (strong)
Lower Mp/Bp than giant covalent and ionic compounds
But higher than simple molecules

49
Q

What is the difference between thermosoftening and thermosetting polymers.

A

Thermosoftening can be remoulded as there are no covalent bonds.
Thermosetting char and burn when heated

50
Q

What is metallic bonding ?

A

The electrostatic attraction between the positive metal ions and negative delocalised electrons.
Between metals
Give up the outer shell electrons
Become positive ions and delocalised electrons

51
Q

Describe metallic structures :

A

High Mp/Bp
Can conduct electricity - delocalised electrons
Regular structure
Malleable as layers slide over each other

giant lattices of positive ions arranged in regular layers, with delocalised electrons free to move throughout the structure.

52
Q

What are allotropes?

A

Different forms of an element in the same state but different atomic arrangements

53
Q

What are the energy transfers in changes of state

A

FROM the compound - freezing/condensing

​ ​TO​ ​a​ ​compound​ ​–​ ​melting,​ ​boiling

54
Q

Why are covalent & ionic bonds brittle?

A

Unlike metals when a force is applied the bond also breaks as there agree no delocalised electrons to move

55
Q

What is the difference between molecules and compounds?

A

Molecules are two or more atoms
Compounds are two or more elements

56
Q

What is a physical property?

A

A feature of a substance that can be measured or observed

57
Q

Why do covalent bonds have a high melting point?

A

They require a large amount of energy to break them

58
Q

What determines the distance that substances travel in chromatography?

A

The strong/weak bonds formed with the mobile /stationary phase

59
Q

What is the difference between mendeleev ‘s periodic table and modern?

A

Mendeleev ‘s was arranged in increasing atomic mass.
Modern day is arrange in increasing atomic number

60
Q

What are some risks of nano particles?

A

So tiny that
🩸can be absorbed by skin/passed into cells
🩸toxic substances stick to surface
🩸take a long time to be broken down by the environment
(Harmful to health & environment)

61
Q

What is the difference between gas chromatography and the others?

A

Gas chromatography can only be used to separate gases.

62
Q

What structure does a metal have?

A

A lattice structure,
Positive ions can slide over each other

63
Q

What is relative molecular mass?

A

The mean mass of one molecule compared to 1/12 the mass of 12g of carbon
(For substances that exist as molecules)

64
Q

What is a locating agent?

A

Analyses colourless substances in paper chromatography, into colourful products that are bus or for inspection.

Eg: ninhydrin spray

65
Q

Why do chemists ‘flute’ their filter paper?

A

Produces a larger SA for filtrate to pass through

66
Q

In chromatography, why do some substances travel further than others?

A

If a component travels further,it forms stronger bonds with the mobile phase than stationary phase

If a component doesn’t travel very far, it forms stronger bonds to the stationary phase than mobile phase

67
Q

What are the mobile /stationary phases for all chromatography?

A
68
Q

Interpret the chromatograph

A
69
Q

What is the size of :
Atoms
Nano particles ?

A
70
Q

What can deduce from the electric configuration?

A

Atomic number
Which group
Which period

71
Q

What are the limitations for the dot and cross diagrams?

A

❌doesn’t indicate the relative sizes of the atoms
❌doesn’t show the lattice structure of an ionic compound (not 3D)
❌doesn’t show how ions are arranged in a space

72
Q

What are the limitations of a ball and stick models?

A

❌fails to show the movement of electrons
❌exaggerates space between the atoms
❌doesn’t show the movement of electrons

73
Q

What are the limitations of 2D models?

A

❌doesn’t show where the ions are located on other layers
❌

74
Q

What are the limitations of 3D models?

A

❌not to scale
❌❌

75
Q

How can you determine the melting point of a substance accurately “

A
  • Heat the substance slowly (so that whole sample is to increase)
  • stir the substance as it melts (ensures that entire sample is at the same temperature )
76
Q

What are some chromatographic methods for distinguishing pure from impure substances ?

A

Gas chromatography
Thin layer
Paper chromatography

77
Q

How many covalent bonds does carbon have?

A

4

78
Q

Describe graphene in terms of structure and bonding

A

Single layer of graphite
Transparent, strong, conducts electrity

79
Q

Describe fullerenes in terms of structure and bonding

A

Fullerenes are where carbon molecules are shaped liked tubes or balls
Nano tubes /buckyballs sheets of graphene rolled into shape

80
Q

Explain the different temperatures at which changes of state occur

A

🟡energy transfers from/to surroundings to
🟡strength of chemical bonds (more energy must be transferred from surroundings to break them)
🟡intermolecular forces are overcome (weakened)
If high melting point many strong bonds in the solid state.
If high boiling point many strong bonds in the liquid state.

81
Q

Why are metals malleable ?

A

In lattice, when a force is applied, the layers of metal ions Slide Over one another, however since the delocalised electrons are free to move, no overall bonds are broken

82
Q

Why might a bulk property of a material be “flexible”?

A

Polymers and simple molecules have weak intermolecular forces which are easily broken. If not arranged in a lattice then will not be brittle

83
Q

How does the SA:V ratio affect its properties?

A

Smaller size = larger SA:V

GCSE Chemistry OCR A (10 decks)

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