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Chemistry Flashcards

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1
Q

What are compounds

A

Substances in which atoms of two or more elements are chemically combined

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2
Q

What does chemical bonding involve

A

Either transferring or sharing electrons in the highest occupied energy levels (shells) of atoms in order to achieve the electronic structure of a noble gas

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3
Q

When are ions formed

A

When atoms form chemical bonds by transferring electrons

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4
Q

What are positively charged ions

A

Atoms that lost electrons

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5
Q

What are negatively charged ions

A

Atoms that gained electrons

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6
Q

What are alkali metals

A

The elements in Group 1

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7
Q

What do alkali metals all react with non metal elements to form

A

Ionic compounds in which the metal ion has single positive charge

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8
Q

What are halogens

A

The elements in Group 7

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9
Q

What do halogens all react with alkali metals to form

A

Ionic compounds in which the halide ions have a single negative charge

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10
Q

What is an ionic compound

A

A giant structure of ions

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11
Q

What are ionic compounds held together by

A

Strong electrostatic forces of attraction between oppositely charged ions that act in all directions of the lattice

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12
Q

When are covalent bonds formed

A

When atoms share pairs of electrons. These bonds between atoms are strong

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13
Q

What are examples of simple molecules that some covalently bonded substances consist of

A

H2, Cl2, O2, HCl, H2O, NH3, CH4

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14
Q

What are examples of macromolecules

A

Diamond and silicon dioxide

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15
Q

What are macromolecules

A

Substances that have giant covalent structures

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16
Q

What do metals consist of

A

Giant structures of atoms arranged in a regular pattern

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17
Q

What can the electrons in the highest occupied energy levels do as a result of being delocalised

A

Be free to move through the whole structure. This corresponds to a structure of positive ions with electrons between the ions holding them together by strong electrostatic attractions

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18
Q

What substances have relatively low melting and boiling points

A

Substances that consist of simple molecules

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19
Q

How strong are the intermolecular forces of simple molecules

A

Weak. It is these intermolecular forces that are overcome, not the covalent bonds, when the substance melts or boils

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20
Q

Why don’t substances that consist of simple molecules conduct electricity

A

Because the molecules do not have an overall electric charge

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21
Q

What are giant ionic lattices

A

Ionic compounds that have regular structures

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22
Q

Why do giant ionic lattices have high melting and boiling points

A

Because of the large amounts of energy needed to break the many strong bonds

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23
Q

What do ionic compounds do when melted or dissolved in water

A

Conduct electricity because the ions are free to move and carry the current

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24
Q

How are macromolecules formed

A

By atoms that share electrons

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25
Q

Why is diamond very hard

A

Because each carbon atom in diamond forms four covalent bonds with other carbon atoms in a giant covalent

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26
Q

Why is graphite soft and slippery

A

Because in graphite, each carbon atom bonds to three others, forming layers. The layers are free to slide over each other because there are no covalent bonds between them

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27
Q

Why is graphite able to conduct heat and electricity

A

Because in graphite one electron from each carbon atom is delocalised. It is these delocalised that allow graphite to conduct heat and electricity

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28
Q

Why is graphite similar to metals

A

It has delocalised electrons

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29
Q

What is the structure of fullerenes based on

A

Hexagonal rings of carbon atoms

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30
Q

What can fullerenes be used for

A

Drug delivery into the body
In lubricants
As catalysts
In nanotubes for reinforcing materials e.g. in tennis rackets

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31
Q

Why do metals conduct heat and electricity

A

Because of the delocalised electrons in their structures

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32
Q

Why can metals be bent and shaped

A

The layers of atoms in metals are able to slide over each other

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33
Q

What are alloys made of

A

2 or more metals

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34
Q

Why are alloys harder than pure metals

A

The different sized atoms of the metals distort the layers in the structure, making it harder for them to slide over each other

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35
Q

What can shape memory alloys do

A

Return to their original shape after bring deformed, e.g. Nitinol used in dental braces

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36
Q

What do the properties of polymers depend on

A

What they’re made of and the conditions under which they are made, e.g. low density and high density poly(ethene) are produced using different catalysts and reaction condition

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37
Q

What do thermosetting polymers consist of

A

Individual, tangled polymer chains with cross-links between them so that they do not melt when heated

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38
Q

What does nanoscience refer to

A

Structures that are 1-100nm in size, of the order of a few hundred atoms

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39
Q

What do nanoparticles show

A

Different properties to the same materials in bulk

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40
Q

What can nanoparticles lead to the development of

A 
New computers
New catalysts 
New coatings
Highly selective sensors
Stronger and lighter construction materials
New cosmetics e.g.  sun tan creams
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41
Q

Why are nanoparticles able to lead to the development of various items

A

Nanoparticles have a high surface area to volume ratio

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42
Q

What are isotopes

A

Atoms of the same element that have a different number of neutrons

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43
Q

What is a mole

A

The relative formula mass of a substance in grams

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44
Q

How can elements and compounds be detected and identified

A

Using instrumental methods. They are accurate, sensitive, rapid and are particularly useful when the sample is small

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45
Q

What can chemical analysis be used to do

A

Identify additives in foods

46
Q

How can artificial colours be detected and identified

A

By paper chromatography

47
Q

What is an example of an instrumental method

A

(GC-MS) Gas chromatography linked to mass spectroscopy

48
Q

What does gas chromatography allow

A

The separation of a mixture of compounds

49
Q

What helps to identify the substance in gas chromatography

A

The time taken for a substance to travel through the column

50
Q

What can the mass spectrometer do

A

Give the relative molecular mass of each of the substances separated in the column
Identify substances very quickly and accurately and can detect small quantities

51
Q

What can be used to identify the substances leaving the end of the column

A

The output from the gas chromatography that can be linked to a mass spectrometer

52
Q

How does gas chromatography 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

53
Q

What does the number of peaks on the output of a gas chromatograph show

A

The number of compounds present

54
Q

What does the position of the peaks on the output show

A

The retention time

55
Q

How is the molecular mass given

A

By the molecular ion peak on the ouput

56
Q

Why is not possible to obtain the calculated amount of a product

A

The reaction may not go to completion because 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 ways different from the expected reaction.

57
Q

How can the rate of reaction be calculated

A

Amount of reactant used / time

Amount of product formed / time

58
Q

When only can chemical reactions occur

A

When reacting particles collide with each other and with sufficient energy

59
Q

What is the activation energy

A

The minimum amount of energy particles must have to react

60
Q

Why does increasing the temperature increase the rate of reaction

A

It increases the speed of the reacting particles so that they collide more frequently and more energetically

61
Q

Why does increasing the pressure of reacting gases increase the rate of reaction

A

It increases the frequency of collisions

62
Q

Why does increasing the concentration of reactants in solutions increase the rate of reactions

A

It increases the frequency of collisions

63
Q

Why does increasing the surface area of solid reactants increase the rate of reaction

A

It increases the frequency of collisions

64
Q

What do catalysts do

A

Change the rate of chemical reactions but are not used up during the reaction

65
Q

What do different reactions need

A

Different catalysts

66
Q

Why are catalysts important

A

They increase the rates of chemical reactions used in industrial processes to reduce costs

67
Q

What happens when chemical reactions occur

A

Energy is transferred to or from the surroundings

68
Q

What is an exothermic reaction

A

One that transfers energy to the surroundings, e.g. combustion, many oxidation reactions and neutralisation

69
Q

What are everyday uses of exothermic reactions

A

Self-heating can (e.g. for coffee) and hand warmers

70
Q

What is an endothermic reaction

A

One that takes in energy from the surroundings

71
Q

What does endothermic reactions include

A

Thermal decomposition and sports injury packs

72
Q

If a reversible reaction is exothermic in one direction …

A

…it is endothermic in the opposite direction. The same amount of energy is transferred in each case

73
Q

What are the state symbols

A

(s), (l), (g) and (aq)

74
Q

Soluble salts can be made by reacting acids with:

A

Metals - not all are suitable (too reactive or not enough)
Insoluble bases - the base is added to the acid until no more will react and the excess solid is filtered off
Alkalis - an indicator can be used to show when the acid and alkali have reacted to make a salt solution

75
Q

Salt solutions can be …

A

…crystallised to produce solid salts

76
Q

How can insoluble salts be made…

A

… By mixing appropriate solutions of ions so that a precipitate is formed

77
Q

What can precipitation be used to do

A

Remove unwanted ions from solutions, for example in treating water for drinking or in treating effluent

78
Q

What are bases

A

Metal oxides and hydroxides

79
Q

What are alkalis

A

Soluble hydroxides

80
Q

What does the particular salt produced in any reaction between an acid and a base or alkali depends on

A

The acid used (HCl produces chlorides, NH3 produces nitrates, H2SO4 produces sulfates)
The metal in the base or alkali

81
Q

Ammonia dissolves in water to produce …

A

An alkaline solution. It is used to produce ammonium salts

82
Q

What are ammonium salts important as

A

Fertilisers

83
Q

What do hydrogen ions do

A

Make solutions acidic

84
Q

What do hydroxide ions do

A

Make solutions alkaline

85
Q

What happens in neutralisation reactions

A

Hydrogen ions with hydroxide ions to produce water

H+ + OH- = H2O

86
Q

What happens when an ionic substance is melted or dissolved in water

A

The ions are free to move about within the liquid or solution

87
Q

What is electrolysis

A

Passing an electric current through ionic substances that are molten, e.g. lead bromide or in solution breaks them down into elements

88
Q

What is the electrolyte

A

The substance that is broken down

89
Q

What happens during electrolysis

A

Positively charged ions move to the negative electrode, and negatively charged ions move to the positive electrode.

90
Q

What is electrolysis used to do

A

Electroplate objects. This may be for a variety of reasons and includes copper plating and silver plating

91
Q

What is reduction

A

When positively charged ions gain electrons at the negative electrode

92
Q

What is oxidation

A

When negatively charged ions lose electrons at the positive electrode

93
Q

What happens if there is a mixture of ions

A

The products formed depend on the reactivity of the elements involved

94
Q

How can reactions at electrodes be represented by

A

Half equations

95
Q

How is aluminium manufactured

A

By the electrolysis of a molten mixture of aluminium oxide and cryolite.
Aluminium forms at the negative electrode and oxygen at the positive electrode.
The positive electrode is made of carbon, which reacts with the oxygen to produce carbon dioxide

96
Q

What does the electrolysis of sodium chloride produce

A

Hydrogen, chlorine and sodium hydroxide solution.

97
Q

Why are the products of electrolysis of sodium chloride important reagents for the chemical industry

A

Sodium hydroxide for the production of soap

Chlorine for the production of bleach and plastics

98
Q

What is the formula of sulphuric acid

A

H2SO4

99
Q

What is the formula of nitric acid

A

HNO3

100
Q

What is the formula of sodium chloride

A

NaCl

101
Q

What is the formula of sodium carbonate

A

Na2CO3

102
Q

What is the formula of sodium nitrate

A

NaNO3

103
Q

Sodium sulfate

A

Na2SO4

104
Q

Magnesium hydroxide

A

Mg(OH)2

105
Q

Isotopes

A

Different atomic forms of the same element, which have the same number of protons but a different number of neutrons

106
Q

Differences in LD and HD polythene

A

LD - made by heating ethene to 200C and has a high pressure

HD - Made at a lower pressure and temperature and uses a catalyst

107
Q

What is LD polythene used for

A

Bags and bottles

108
Q

What is HD polythene used for

A

Water tanks and pipeline

109
Q

Acid + Metal Oxide ->

A

Salt + Water

110
Q

Acid + Metal hydroxide ->

A

Salt + Water

Additional Science (3 decks)

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