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GCSE Chemistry > C2a > Flashcards

C2a Flashcards

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0
Q

What is an isotope?

A

Isotopes are different atomic forms of the same element, which have the same number of protons but different numbers of neutrons

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1
Q

What are compounds?

A

Compounds are atoms of two or more elements chemically bonded together. It is difficult to separate the elements

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3
Q

What is ionic bonding?

A

Atoms lose or gain electrons to form ions which are strongly attracted to one another

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4
Q

Why do atoms react?

A

To get a full outer shell

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5
Q

Describe the structure of a giant ionic lattice

A

1) Ions closely packed together
2) In a regular arrangement
3) With strong ionic bonds in all directions

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6
Q

Why do giant ionic lattices have a high mpt?

A

Strong electrostatic forces of attraction in all directions. A lot of (heat) energy is needed to break these bonds

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7
Q

Why are giant ionic lattices brittle?

A

When layers are hit, they move and similar charges are next to each other. These repel so the substance breaks apart

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8
Q

Do giant ionic lattices conduct electricity?

A

Only when molten or dissolved as ions are free to move

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9
Q

What is covalent bonding?

A

Bonding between two or more non-metals, in which they share electrons so they both have a full outer shell

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10
Q

Which atoms form diatomic molecules?

A

All group 7, H, N and O

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11
Q

Describe the structure of simple molecular substances

A

1) Strong covalent bonds (intramolecular forces)
2) Weak intermolecular forces
3) No ions

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12
Q

Why are simple molecular substances liquids or gases at room temperature?

A

Weak intermolecular forces so not much (heat) energy is needed to separate them

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13
Q

Do simple molecular substances conduct electricity?

A

No as no ions

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14
Q

What is another name for giant covalent structures? Give 3 examples

A

Macromolecules

Diamond, Silicon dioxide, Graphite

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15
Q

Describe the structure of diamond

A

1) Each carbon atom forms 4 covalent bonds

2) Rigid structure (hardest natural substance)

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16
Q

Describe the structure of silica

A

1) Strong covalent bonds

2) Makes sand

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17
Q

Can diamond and silica conduct electricity?

A

Not even when molten or dissolved as no free ions or electrons

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18
Q

Describe the structure of graphite

A

1) Each carbon atom forms 3 covalent bonds

2) Arranged in layers

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19
Q

Why is graphite soft and slippery?

A

It is made up of layers that can slide over each other

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20
Q

Can graphite conduct electricity?

A

Yes because each carbon atom leaves one delocalised electron

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21
Q

Why do giant covalent substances have high mpts?

A

Strong covalent bonds so a lot of (heat) energy is needed to break the bonds

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22
Q

Describe the structure of a metal

A

1) Positive ions in regular arrangement
2) In a sea of free electrons
3) Opposite forces hold it together

23
Q

Why are metals malleable?

A

Layers can slide over each other without breaking

24
Q

Do metals conduct electricity?

A

Yes because delocalised electrons

25
Q

Why are alloys harder than pure metals?

A

Different sized atoms disrupt the regular arrangement so layers can’t slide over each other

26
Q

Give an example of a smart material and what it is used for

A

Nitol (nickle + titanium) - shape memory

When cool it can bend, when heated it goes to remembered shape - used in glasses and braces

27
Q

What are fullerenes?

A

Carbon nanoparticles
Strong covalent bonds hold it together in balls/ tubes made from hexagonal rings
Used to reinforce graphite in tennis rackets

28
Q

Why can nanotubes be used as lubricants?

A

Tubes can roll over each other as there are no bonds between tubes. Lubricant coatings reduce friction in artificial joints/ gears

29
Q

What can nanoparticles be used for?

A 
Catalysts - high SA:volume
Highly specific sensors e.g. water purification
Cosmetics - no white mark deodorant
Deliver drugs in body
Tiny electric circuits
30
Q

What is the structure of thermosoftening polymers?

A

Strong covalent bonds to make chains

Weak intermolecular forces - chains free to slide

31
Q

What are the qualities of thermosoftening polymers?

A

Low mpt
Easily remoulded
Soft + felxible

32
Q

How are low density polymers made?

A

E.g. bags + bottles
High temp (200)
High pressure

33
Q

What is the structure of thermosetting polymers?

A

Strong covalent bonds

Crosslinks provide stronger intermolecular forces

34
Q

What are the qualities of thermosetting polymers?

A

High mpt
Can’t be remoulded
Hard + rigid

35
Q

How are high density polymers made?

A

E.g. drainpipes
Low temp + pressure
Catalyst

36
Q

What is Ar?

A

Relative atomic mass - how heavy atoms are compared to C12 (top number)

37
Q

What is Mr?

A

Relative formula mass - all Ars of a compound added together

38
Q

What is a mole?

A

The Mr of a substance in grams

39
Q

What is the equation for finding moles?

A

Moles = mass/Mr

40
Q

How do you find experimental masses?

A

1) Balance equation
2) Work out moles
3) Ratio using balanced equation
4) Moles * Mr

41
Q

What is the empirical formula?

A

The experimentally derived ratio of the amount of atoms in a compund

42
Q

How do you find the empirical formula?

A

1) Write down element and data
2) Divide data by Ar
3) Divide by smallest
4) Make into a whole number

43
Q

What is the equation for % yield?

A

% yield = actual/ theoretical * 100

44
Q

Why is a high % yield important?

A

Save resources, money, time, energy

45
Q

Why is % yield never 100%?

A

1) Products remain on filter paper / glassware
2) Unexpected reactions - useless products
3) Reversible reactions - reaction where the products can themselves react to become the original reactants

46
Q

In reversible reactions, what is the heat transfer?

A

Exothermic one way means endothermic the other

47
Q

What is paper chromatography?

A

A method of chemical analysis used to separate substances e.g. dyes

48
Q

How is paper chromatography used?

A

Pencil (insoluble) baseline on filter paper
Shallow solvent in beaker
Paper just in solvent

49
Q

What is the Rf value?

A

Distance travelled by a dye

50
Q

Why are machines often used in chemical analysis?

A

Faster, more accurate, more sensitive

51
Q

How does gas chromatography work?

A

Gas carries substance through column

Different masses so different speeds so substance separates

52
Q

What is retention time?

A

The time of a substance taken to reach the detector

53
Q

How can you tell the number of compounds in a substance?

A

Number of peaks

54
Q

What does a mass spectrometer do?

A

Work out the Mr of a compound (molecular ion peak)

GCSE Chemistry (2 decks)

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