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Chemistry Flashcards

(110 cards)

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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
Why is diamond very hard
Because each carbon atom in diamond forms four covalent bonds with other carbon atoms in a giant covalent
26
Why is graphite soft and slippery
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
27
Why is graphite able to conduct heat and electricity
Because in graphite one electron from each carbon atom is delocalised. It is these delocalised that allow graphite to conduct heat and electricity
28
Why is graphite similar to metals
It has delocalised electrons
29
What is the structure of fullerenes based on
Hexagonal rings of carbon atoms
30
What can fullerenes be used for
Drug delivery into the body In lubricants As catalysts In nanotubes for reinforcing materials e.g. in tennis rackets
31
Why do metals conduct heat and electricity
Because of the delocalised electrons in their structures
32
Why can metals be bent and shaped
The layers of atoms in metals are able to slide over each other
33
What are alloys made of
2 or more metals
34
Why are alloys harder than pure metals
The different sized atoms of the metals distort the layers in the structure, making it harder for them to slide over each other
35
What can shape memory alloys do
Return to their original shape after bring deformed, e.g. Nitinol used in dental braces
36
What do the properties of polymers depend on
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
37
What do thermosetting polymers consist of
Individual, tangled polymer chains with cross-links between them so that they do not melt when heated
38
What does nanoscience refer to
Structures that are 1-100nm in size, of the order of a few hundred atoms
39
What do nanoparticles show
Different properties to the same materials in bulk
40
What can nanoparticles lead to the development of
``` New computers New catalysts New coatings Highly selective sensors Stronger and lighter construction materials New cosmetics e.g. sun tan creams ```
41
Why are nanoparticles able to lead to the development of various items
Nanoparticles have a high surface area to volume ratio
42
What are isotopes
Atoms of the same element that have a different number of neutrons
43
What is a mole
The relative formula mass of a substance in grams
44
How can elements and compounds be detected and identified
Using instrumental methods. They are accurate, sensitive, rapid and are particularly useful when the sample is small
45
What can chemical analysis be used to do
Identify additives in foods
46
How can artificial colours be detected and identified
By paper chromatography
47
What is an example of an instrumental method
(GC-MS) Gas chromatography linked to mass spectroscopy
48
What does gas chromatography allow
The separation of a mixture of compounds
49
What helps to identify the substance in gas chromatography
The time taken for a substance to travel through the column
50
What can the mass spectrometer do
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
What can be used to identify the substances leaving the end of the column
The output from the gas chromatography that can be linked to a mass spectrometer
52
How does gas chromatography work
Different substances, carried by a gas, travel through a column packed with a solid material at different speeds, so that they become separated
53
What does the number of peaks on the output of a gas chromatograph show
The number of compounds present
54
What does the position of the peaks on the output show
The retention time
55
How is the molecular mass given
By the molecular ion peak on the ouput
56
Why is not possible to obtain the calculated amount of a product
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
How can the rate of reaction be calculated
Amount of reactant used / time | Amount of product formed / time
58
When only can chemical reactions occur
When reacting particles collide with each other and with sufficient energy
59
What is the activation energy
The minimum amount of energy particles must have to react
60
Why does increasing the temperature increase the rate of reaction
It increases the speed of the reacting particles so that they collide more frequently and more energetically
61
Why does increasing the pressure of reacting gases increase the rate of reaction
It increases the frequency of collisions
62
Why does increasing the concentration of reactants in solutions increase the rate of reactions
It increases the frequency of collisions
63
Why does increasing the surface area of solid reactants increase the rate of reaction
It increases the frequency of collisions
64
What do catalysts do
Change the rate of chemical reactions but are not used up during the reaction
65
What do different reactions need
Different catalysts
66
Why are catalysts important
They increase the rates of chemical reactions used in industrial processes to reduce costs
67
What happens when chemical reactions occur
Energy is transferred to or from the surroundings
68
What is an exothermic reaction
One that transfers energy to the surroundings, e.g. combustion, many oxidation reactions and neutralisation
69
What are everyday uses of exothermic reactions
Self-heating can (e.g. for coffee) and hand warmers
70
What is an endothermic reaction
One that takes in energy from the surroundings
71
What does endothermic reactions include
Thermal decomposition and sports injury packs
72
If a reversible reaction is exothermic in one direction ...
...it is endothermic in the opposite direction. The same amount of energy is transferred in each case
73
What are the state symbols
(s), (l), (g) and (aq)
74
Soluble salts can be made by reacting acids with:
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
Salt solutions can be ...
...crystallised to produce solid salts
76
How can insoluble salts be made...
... By mixing appropriate solutions of ions so that a precipitate is formed
77
What can precipitation be used to do
Remove unwanted ions from solutions, for example in treating water for drinking or in treating effluent
78
What are bases
Metal oxides and hydroxides
79
What are alkalis
Soluble hydroxides
80
What does the particular salt produced in any reaction between an acid and a base or alkali depends on
The acid used (HCl produces chlorides, NH3 produces nitrates, H2SO4 produces sulfates) The metal in the base or alkali
81
Ammonia dissolves in water to produce ...
An alkaline solution. It is used to produce ammonium salts
82
What are ammonium salts important as
Fertilisers
83
What do hydrogen ions do
Make solutions acidic
84
What do hydroxide ions do
Make solutions alkaline
85
What happens in neutralisation reactions
Hydrogen ions with hydroxide ions to produce water | H+ + OH- = H2O
86
What happens when an ionic substance is melted or dissolved in water
The ions are free to move about within the liquid or solution
87
What is electrolysis
Passing an electric current through ionic substances that are molten, e.g. lead bromide or in solution breaks them down into elements
88
What is the electrolyte
The substance that is broken down
89
What happens during electrolysis
Positively charged ions move to the negative electrode, and negatively charged ions move to the positive electrode.
90
What is electrolysis used to do
Electroplate objects. This may be for a variety of reasons and includes copper plating and silver plating
91
What is reduction
When positively charged ions gain electrons at the negative electrode
92
What is oxidation
When negatively charged ions lose electrons at the positive electrode
93
What happens if there is a mixture of ions
The products formed depend on the reactivity of the elements involved
94
How can reactions at electrodes be represented by
Half equations
95
How is aluminium manufactured
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
What does the electrolysis of sodium chloride produce
Hydrogen, chlorine and sodium hydroxide solution.
97
Why are the products of electrolysis of sodium chloride important reagents for the chemical industry
Sodium hydroxide for the production of soap | Chlorine for the production of bleach and plastics
98
What is the formula of sulphuric acid
H2SO4
99
What is the formula of nitric acid
HNO3
100
What is the formula of sodium chloride
NaCl
101
What is the formula of sodium carbonate
Na2CO3
102
What is the formula of sodium nitrate
NaNO3
103
Sodium sulfate
Na2SO4
104
Magnesium hydroxide
Mg(OH)2
105
Isotopes
Different atomic forms of the same element, which have the same number of protons but a different number of neutrons
106
Differences in LD and HD polythene
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
What is LD polythene used for
Bags and bottles
108
What is HD polythene used for
Water tanks and pipeline
109
Acid + Metal Oxide ->
Salt + Water
110
Acid + Metal hydroxide ->
Salt + Water

Additional Science (3 decks)

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