2.1 Flashcards

1
Q

What is an element?

A

Same atoms

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2
Q

What is a compound?

A

Different atoms chemically bonded

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3
Q

How do you split a compound ?

A

Chemical reaction

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4
Q

What is in a mixture?

A

Different elements or compounds not chemically combined

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5
Q

How do you separate a mixture?

A

Physical techniques

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6
Q

What physical techniques can separate mixtures?

A

Filtration
Distillation
Crystallisation

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7
Q

What is a molecule?

A

Any of the same elements chemically joined

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8
Q

Why is found in the nucleus of an atom?

A

Protons

Neutrons

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9
Q

Where are the electrons found in the atomic structure ?

A

Shells

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10
Q

What is the charge of an atom?

A

0

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11
Q

Why is there no overall charge of atoms?

A

Electrons are cancelled out by protons

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12
Q

On the periodic table which number is the atomic number?

A

Smaller number

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13
Q

What is the atomic number

A

Number of protons

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14
Q

Where is the mass number on the periodic table?

A

Biggest number

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15
Q

What is the mass number?

A

Total of protons and neutrons in the nucleus

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16
Q

How do you calculate number of neutrons ?

A

Mass number - atomic number

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17
Q

Why do elements react?

A

Full outer shell

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18
Q

What are boiling points of ionic compounds? Why?

A

Very high

Electrostatic forces require lots of heat energy to break

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19
Q

Can ionic compounds conduct electricity ? Why?

A

No

Ions cannot move because of the electrostatic forces of attraction.

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20
Q

When can ionic compounds conduct electricity? Why?

A

Molten or dissolved in water

Breaks electrostatic forces
Ions can now move and carry current

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21
Q

Why does ionic bonding contain?

A

Transfer of electrons of non metals and metals

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22
Q

What does covalent bonding contain?

A

Shared electrons of non metals

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23
Q

What are the properties of simple covalent molecules?

A

Low melting and boiling points
Usually gases or liquids at room temp
Do not conduct electricity

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24
Q

What holds the atoms in each covalent molecule together?

A

Strong covalent bonds

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25
Q

What holds the molecules together in a covalent molecule?

A

Weak intermolecular forces

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26
Q

Why does it not take much energy to turn a simple covalent molecule into a gas?

A

Weak intermolecular forces are easily broken with little energy

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27
Q

Why do simple covalent molecules not conduct electricity?

A

They do not have an overall electric charge

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28
Q

What are the 4 giant covalent molecules?

A

Diamond
Graphite
Fullerenes
Silicon dioxide

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29
Q

What is diamond made of and how are these atoms bonded?

A

Carbon atoms with 4 covalent bonds to other carbon atoms

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30
Q

What are the properties of diamond and why do these occur?

A

Extremely hard
Very high melting point

Because of the large number of strong covalent bonds

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31
Q

What is graphite made of and how are the atoms bonded?

A

Carbon atoms with 3 covalent bonds

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32
Q

Why is graphite very soft?

A

It has layers which are not strongly held together as there aren’t covalent bonds between layers - only weak intermolecular forces
Layers can then slide over each other

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33
Q

Why can graphite conduct electricity and heat?

A

Each atom has a spare electron due to only having 3 covalent bonds.
The delocalised electrons can move and conduct electricity and heat.

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34
Q

What can fullerenes be used for?

A

Drug delivery into the body
Lubricants
Catalysts
Nanotubes for reinforcing materials e.g. Tennis rackets

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35
Q

How are fullerenes structured?

A

Hexagonal rings of carbon

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36
Q

What elements does silicon dioxide contain?

A

Oxygen and silicon

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37
Q

Why does silicon dioxide have a high melting point?

A

Contains a large number of covalent bonds

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38
Q

What are the forces between oppositely charged ions called?

A

Strong electrostatic forces

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39
Q

Why can metals conduct heat and electricity?

A

Because of their delocalised electrons

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40
Q

Why can metals be bent and shaped?

A

The layers of atoms slide over each other

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41
Q

What are alloys?

A

2 or more different metals

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42
Q

Why are alloys harder than pure metals?

A

Different story sized atoms of metals distort the layers in the structure, making it more difficult for layers to slide over each other

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43
Q

What do shape memory alloys do?

Give an example.

A

Return to their original shape

Nitinol is used in dental braces

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44
Q

How are thermosoftening polymers structured?

A

Individual, tangled polymer chains with weak intermolecular forces between them.

45
Q

How are thermosetting polymers structured?

A

Polymer chains with cross-links between them so they do not melt when heated.

46
Q

What happens when a thermosoftening polymer is heated? Why?

What happens when it is cooled?

A

It melts when heated because the intermolecular forces are easily broken.
Turns back to solid when cooled.

47
Q

What happens when a thermosetting polymer is heated? Why?

A

Does not melt.

Strong cross links are not broken by heat.

48
Q

What’s the difference between low density ploy(ethene) and high density poly(ethene)?

A

They are produced using different catalysts and reaction conditions.

LDPE = weak, lower usable temperature (85 degrees), many branches on polymer molecules

HDPE = strong, higher usable temperature (120 degrees), few branches on polymer molecules

49
Q

What is nanoscience?

A

Structures that are 1-100 nanometres in size

50
Q

What are nanoparticles used for?

A
Catalysts
Coatings e.g. Paints
Cosmetics e.g. Sun creams, deodorants 
Stronger and lighter construction materials
Highly selective sensors 
New computers
51
Q

How do nanoparticles work?

A

They have a high surface area to volume ratio

52
Q

What are the masses of protons, neutrons and electrons?

A
Proton = 1
Neutron = 1
Electron = very small
53
Q

What is the mass number?

A

Total number of protons and neutrons

54
Q

What is an isotope?

A

Atoms of the same element with a different number of neutrons

55
Q

What is the relative atomic mass (Ar) of an element?

A

It compares the mass of the atoms of the element with the 12C (carbon 12) isotope.
It is an average value for the isotopes of the element.

56
Q

What is the relative formula mass (Mr) of a compound?

A

The sum of the relative atomic masses of the atoms in the numbers shown in the formula

57
Q

What is the relative formula mass of a substance in grams known as?

A

One mole of that substance

58
Q

What is good about instrumental methods?

A

Accurate
Sensitive
Rapid
Useful when the amount of sample is small

59
Q

What technique is used to detect artificial colours in food?

A

Paper chromatography

60
Q

How does gas chromatography linked to mass spectroscopy work?

A

Different substances, carried by a gas, travel through a column packed with a solid material at different speeds, so that they become separated
Number of peaks on the output of a gas chromatograph shows the number of compounds present
Position of the peaks on the output indicates the retention time
Mass spectrometer can identify substances very quickly and accurately and can detect very small quantities

61
Q

What can a mass spectrometer also do?

A

Give the relative molecular mass of each of the substances separated in the column
This is given by the molecular ion peak

62
Q

How do you calculate the percentage of an element in a compound?

A

Use the relative mass of the element in the formula and the relative formula mass of the compound.
(Mass of element / Relative formula mass) x 100%

63
Q

How do you calculate the empirical formula of a compound?

A

Use the percentages or masses of the elements in the compound.
Find the ratio of elements in the compound

64
Q

Why is it not always possible to obtain the calculated amount of product?

A

The reaction may not go to completion as it is reversible

Some of the product may be lost when it is separated from the reaction mixture

Some of the reactants may react in way different from the expected reaction

65
Q

What is the percentage of product obtained called?

A

Yield

66
Q

How do you calculate percentage yield?

A

(Actual mass of product / Expected mass of product) x 100%

67
Q

Hoe is a reversible reaction represented?

A

2 arrows in opposite directions

68
Q

What are the 2 ways of working out rate of reaction?

A

Amount of product formed / time

Amount of reactant used / time

69
Q

What is activation energy?

A

The minimum amount of energy particles must have to react

70
Q

What are the 4 ways of increasing the rate of reaction?

A

Increase temp
Increase pressure of reacting gases
Increase concentration of reactants in solutions
Increase surface area of solid reactants

71
Q

How does increasing temperature increase the rate of reaction?

A

Increases the speed of reacting particles so they collide more frequently and more energetically

72
Q

How does increasing pressure of reacting gases increase the rate of reaction?

A

Increases the frequency of collisions

73
Q

How does increasing the concentration of reacts in solutions increase rate of reaction?

A

Increases frequency of collisions

74
Q

How does increasing the surface area of solid reactants increase rate of reaction?

A

Increases frequency of collisions

75
Q

What are catalysts?

A

Something that changes the rate of reaction but is not used up during the reaction

76
Q

What do different reactions need?

A

Different catalysts

77
Q

Why are catalysts important in industrial processes?

A

They speed up the rate of reaction so reduce costs

78
Q

What happens during chemical reactions in terms of energy?

A

Energy is transferred to or from the surroundings

79
Q

What is an exothermic reaction?

A

A reaction that transfers energy to the surroundings

80
Q

Give examples of exothermic reactions

A
Combustion 
Neutralisation
Oxidation reactions
Self-heating cans
Hand warmers
81
Q

What is an endothermic reaction?

A

A reaction that takes in energy from the surroundings

82
Q

Give examples of endothermic reactions

A

Thermal decomposition

Sports injury packs

83
Q

What happens if a reversible reaction is exothermic in one direction?

A

It is endothermic in the other direction

84
Q

What does (s), (l), (g) and (aq)mean?

A

Solid
Liquid
Gas
Aqueous

85
Q

What can you react with acids to make soluble salts? And how do you react them?

A

Metals - not all metals are suitable (some too reaction and some not enough)

Insoluble bases - base is added to acid until no more will react and the excess is filtered off

Alkalis - an alkali can be used to show when the acid and alkali have completely reacted to produce a salt solution

86
Q

How can you produce solid salts from salt solutions?

A

Crystallise the salt solution

87
Q

How do you make insoluble salts?

A

Mixing appropriate solutions of ions so that a precipitate is formed

88
Q

How can precipitate be used?

A

To remove unwanted ions from solutions e.g. In treating water for drinking or treating sewage

89
Q

What is a base?

A

Metal oxides and hydroxide

90
Q

What is an alkali?

A

A soluble hydroxide

91
Q

The particular salt produced between an acid and a base/alkali depends on…

A

The acid used

The metal in the base or alkali

92
Q

Which salts are produced by:
Hydrochloric acid
Nitric acid
Sulfuric acid

A

Chlorides
Nitrates
Sulfates

93
Q

What is formed when ammonia dissolves in water? What is this used to produce?

A

An alkaline solution

Ammonium salts

94
Q

What are ammonium salts important for?

A

Fertilisers

95
Q

What do hydrogen ions make solutions go?

What do hydroxide ions make solutions go?

A

Acidic

Alkaline

96
Q

What is the pH scale?

A

A measure of the acidity or alkalinity of a solution

97
Q

What happens in a neutralisation reaction?

A

Hydrogen ions react with hydroxide ions to produce water

98
Q

What happens to the ions when an ionic substance is melted or dissolved in water?

A

They are free to move in the liquid or solution

99
Q

What is electrolysis?

A

When you pass an electric current through ionic substances that are molten or in solution to break them down into elements

100
Q

What is an electrolyte?

A

The substance broken down by electrolysis

101
Q

What happens to the positively charged ions during electrolysis?
What about the negatively charged ions?

A

Move to the negative electrode (cathode)

Move to the positive electrode (anode)

102
Q

What is a use of electrolysis?

Give examples of this use.

A

Electroplating

E.g. Copper plating
Silver plating

103
Q

What happens at the negative electrode?

A

Positively charged ions gain electrons (reduction)

104
Q

What happens at the positive electrode?

A

Negatively charged ions lose electrons (oxidation)

105
Q

If there is a mixture of ions, what do the products formed depend on?

A

The reactivity of the elements involved

106
Q

How is aluminium manufactured using electrolysis?

A

Electrolysis of molten mixture of aluminium oxide and cryolite
Aluminium forms at negative electrode
Oxygen forms at positive electrode
Positive electrode is made of carbon, which reacts with oxygen to form carbon dioxide

107
Q

What does the electrolysis of sodium chloride solution produce?

A

Hydrogen
Chlorine
Sodium hydroxide solution

108
Q

How are sodium hydroxide solution and chlorine important reagents for the chemical industry?

A

Sodium hydroxide = production of soap

Chlorine = production of bleach and plastics

109
Q

Why is cryolite used to extract aluminium?

A

It reduces the energy costs as molten cryolite has a lower melting point the aluminium oxide