Science A (Core): Chemistry Flashcards
1
Q
Draw and label an atom
A
2
Q
What does the periodic table contain?
A
Elements
3
Q
What do these terms means:-
Atom
Molecule
Element
Compound
Mixture
A
Atom – single particle which are the building blocks of all materials
Molecule – group of atoms bound together representing the smallest unit of a chemical compound
Element – pure substance with only 1 type of atom (e.g. gold)
Compound – 2 or more elements chemically bound (e.g. carbon dioxide)
Mixture – more than 1 element or compound not chemically bound (e.g. air)
4
Q
What are the symbols for the following atoms: -
Oxygen
Nitrogen
Chlorine
Hydrogen
Sodium
Copper
Potassium
Helium
Calcium
Zinc
Iron
Carbon
A
Oxygen (O)
Nitrogen (N)
Chlorine (Cl)
Hydrogen (H)
Sodium (Na)
Copper (Cu)
Potassium (K)
Helium (He)
Calcium (Ca)
Zinc (Zn)
Iron (Fe)
Carbon (C)
5
Q
What happens to atoms when they chemically react to form a compound?
A
They share, give away, or take electrons
6
Q
What are the names of these compounds, and which atoms are found in them?
H2O
CaCO3
H2SO4
HCl
CO2
A
Water (H2O)
Calcium carbonate (CaCO3)
Sulfuric acid (H2SO4)
Hydrochloric acid (HCl)
Carbon dioxide (CO2)
7
Q
What is limestone used to produce?
A
Cement, concrete, glass and building materials
Heated with clay = cement
Cement + sand = mortar
Sand + gravel = concrete
8
Q
What is a quarry, and what are the pros and cons of quarrying for materials?
A
A quarry is a place where large amounts of raw materials such as ores and limestone are removed from the ground
Pros – employment / economic benefits
Cons – noisy / ugly / habitat destruction
9
Q
What is the equation for when a metal reacts with water?
A
Metal + Water → Metal Hydroxide + Hydrogen
10
Q
What is the equation for when a metal reacts with air?
A
Metal + Oxygen → Metal Oxide
11
Q
What are cations?
A
Cations are atoms which lose electrons (having less electrons than protons) which have a positive charge
12
Q
What are anions?
A
Anions are atoms which gain electrons (having more electrons than protons) which have a negative charge
13
Q
Do metal atoms lose or gain electrons?
A
Metal atoms lose electrons becoming positive in charge (cations)
14
Q
Do non-metal atoms lose or gain electrons?
A
Non-metal atoms gain electrons becoming negative in charge (anions)
15
Q
How does an electrostatic precipitator work?
A
- Smoke particles pick up a negative charge
- Smoke particles are attracted to the collecting plates
- Collecting plates are knocked to remove the smoke particles
16
Q
What happens in the reaction between sodium and chlorine?
A
sodium + chlorine → sodium chloride
17
Q
What happens in the reaction between magnesium and oxygen?
A
magnesium + oxygen → magnesium oxide
18
Q
What happens in the reaction between calcium and chlorine?
A
calcium + chlorine → calcium chloride
19
Q
How is pure iron made into steel?
How does the change in structure affect its properties?
A
Add carbon – this means the atoms cannot slide past one another as easily, making it stronger (steel)
High carbon steel = hard
Low carbon steel = easily shaped
Stainless steel = resistant to corrosion
20
Q
Why is the extraction of aluminium and titanium so expensive?
A
There are many stages and lots of energy is needed
21
Q
What is an alloy and why are they used?
Give some examples
A
Alloys are mixtures of metals with other elements, e.g. iron + carbon → steel
They have a combination of properties, e.g. bronze, brass, steel etc…
22
Q
What is a smart alloy and why are they used?
Give some examples
A
Smart alloys can return to their original shape after being deformed – e.g. glasses and braces
23
Q
Where are the transition metals found on the periodic table?
What are the general properties of the transition metals, and what are they used for?
A
Transition metals are found in the middle of the periodic table and used for building materials
Easily shaped
Hard (strong)
Good conductors (heat + electricity)
Less reactive
24
Q
How is copper usually extracted?
What is it used for?
A
Electrolysis extracts copper
Copper is used for electrical cables
25
What is an ore?
A rock with enough metal to make it worthwhile extracting the metal from
26
Why is it important to recycle?
Because we only have a limited supply of resources, e.g. oil (recycle plastic) and aluminium (recycle ores) and it is better for the environment
27
Some metals can be extracted from ores using carbon – how does this work?
If carbon is more reactive that the metal, it reacts with the oxygen to purify it
28
Give 2 metals that carbon can be used to extract
Give 2 metals that carbon cannot be used to extract
Carbon can extract anything less reactive than itself (e.g. iron and lead)
Carbon cannot extract anything more reactive than itself (e.g. magnesium and aluminium)
29
Why are aluminium and titanium such useful metals?
Why can they not be extracted with carbon?
They have low density and are resistant to corrosion
30
What are the properties of pure iron?
Explain why this is
Easily shaped and too soft for most jobs because of the regular arrangement of the atoms (they can slide past one another)
31
What is a covalent bond?
A bond formed between two non-metal atoms, sharing electrons
32
Draw an electron diagram showing how hydrogen bonds
Hydrogen atoms can each form one covalent bond
One pair of electrons is shared in a hydrogen molecule (H2)
33
Draw an electron diagram showing how oxygen bonds
Oxygen atoms can each form two covalent bonds
Two pairs of electrons are shared in an oxygen molecule (O2) – a double bond
34
Draw an electron diagram showing how water bonds
Hydrogen atoms can each form one covalent bond, while oxygen atoms can each form two covalent bonds
Two pairs of electrons are shared in a water molecule (H2O)
35
What are they signs of a chemical reaction
Signs of a chemical reaction include: -
A change in colour
A gas coming off (you may see fizzing or bubbling)
A change in temperature (the reaction mixture may get hotter)
A solid may be formed when two solutions are mixed together
36
What are the properties of the transition metals?
They are metals
They form coloured compounds
They are good conductors of heat and electricity
They can be hammered or bent into shape easily
They are less reactive than alkali metals
They have high melting points (but mercury is a liquid at room temperature)
They are hard and tough
They have high densities
37
Where are the transition metals found on the periodic table?
The transition metals are found in the large block between groups II and groups III in the periodic table
38
What is electrolysis?
Electrolysis is a way to extract reactive metals from their ores, however it is very expensive as a large amount of electricity is required
39
What are the steps involved in electrolysis?
Make the metal ore molten to release the metal ions so they can move
Electrodes cause the metal ions (+ve) to flow to the –ve electrode
At the cathode the ions pick up spare electrons turning from ions into atoms where they sink and can be collected
40
Where do the ions go during electrolysis?
Positively charged ions move to the –ve electrode whilst negatively charged ions move to the +ve electrode
41
What is phytomining?
Phytomining uses plants to absorb naturally occurring metal compounds (including copper) when they grow
Once a significant amount of metal compound has been absorbed the plants are burned, producing ash which contains the metal compounds
42
What is bioleaching?
Bioleaching uses bacteria to produce leachate solutions that contain metal compounds…
Some bacteria can live by using the energy of the bonds between sulfur and copper – in doing so this separates the metal from the ore
The process is efficient, but very slow!
43
What is the overall charge of an atom and what are the charges of the sub-atomic particles?
Atoms have a neutral charge (they have the same number of protons as electrons)
Protons are positive
Electrons are negative
Neutrons are neutral
44
How can we work out the proton, electron and neutron numbers of an atom, e.g. potassium: -
The periodic table shows us the atomic number (bottom number = protons (and therefore electrons) as well as the atomic mass (top number = protons + neutrons)
Proton number = atomic number
Electron number = atomic number
Neutron number = atomic mass – atomic number
45
How do electrons fill up in their shells?
How many electrons would you find in the outer shell of a group 1, group 2, group 7 and group 8 element?
Electrons occupy the lowest energy shell before filling the next, with a maximum of 2 e- in shell 1; 8 e- in shell 2; 8 e- in shell 3
Group 1 elements = 1 e- in outer shell
Group 2 elements = 2 e- in outer shell
Group 7 elements = 7 e- in outer shell
Group 8 elements = 8 e- in outer shell
46
Where are the metals and non-metals found on the periodic table?
Metals are found on the left hand side, non-metals on the right
47
What happens to the mass of materials during a chemical reaction?
Mass stays the same – it does not change in a chemical reaction
48
Why are the noble gases in group 8 unreactive?
\*(Group 8 also known as group 0)
They have a full outer shell so do not need to gain or lose any electrons, so are unreactive
49
Why are some metals such as gold and silver found as the metal itself within the Earth without the need for extraction?
Some metals such as gold and silver are extremely unreactive, and can be found within the Earth as the metal itself without the need for chemical extraction from an ore
50
How pure is iron from a blast furnace and what is the effect of the impurities?
96% pure – the impurities cause brittleness in the iron
51
What are the properties of copper?
Good conductor of heat and electricity, hard but malleable, does not react with water etc…
52
What is the chemical name and chemical formula for limestone
CaCO3
53
What happens during the thermal decomposition of limestone?
What does calcium oxide and water react to form?
Calcium Carbonate → Calcium Oxide + Carbon Dioxide
Calcium hydroxide (a base to neutralise acids)
54
What do metal carbonates and acids form?
Carbon dioxide, water and salt
55
What is calcium hydroxide?
How is it used and what does it test for?
Calcium hydroxide is limewater
It tests for the presence of carbon dioxide (goes cloudy)
56
What does calcium hydroxide + carbon dioxide form?
Calcium carbonate
57
How can hydrocarbons be broken down into smaller molecules?
Cracking
58
What is an alkane?
Give an example and draw it
An alkane is a hydrocarbon, e.g. ethane
59
What kind of reaction happens when large hydrocarbons are broken down?
Thermal decomposition
60
What is the general formula for an alkane?
CnH2n+2
61
What is the general formula for an alkene?
Give an example and draw it
CnH2n – e.g. propene
62
How can you test for an alkene?
Bromine water – goes clear
63
What conditions are needed for cracking of large hydrocarbons?
Cracking – heat hydrocarbons and vapourise them, then pass these vapours over a catalyst
64
What are the products of cracking useful for?
Useful as fuels
65
How can ethanol be made from ethene?
Ethene reacted with steam and in the presence of a catalyst = ethanol
66
What is polymerisation?
Polymerisation is when small molecules are joined to make longer, more useful molecules (e.g. ethane makes poly(ethane))
67
Give 2 examples of polymers
Poly(ethane) and poly(propene)
68
What determines the properties of polymers?
What they are made from and the conditions under which they are made
69
Give 6 uses of polymers
New packaging, waterproof coatings, dental-polymers, hydrogels, smart materials (shape memory polymers)
70
What are the problems with polymers?
Often polymers are not biodegradable causing issues with disposal
71
How can vegetable oil be extracted from fruit and seeds?
Crushing, pressing and distilling
72
Why are vegetable oils an important part of our diet?
They provide us with nutrient and energy
73
Why are emulsions useful?
They are thicker than oil or water and have uses dependent on their special properties – an emulsion is a suspension of fat droplets in water (or some other liquid)
74
What uses do emulsions have?
Better texture, coating ability and appearance used in salad dressings and ice cream
75
Vegetable oils that contain double bonds can be detected by what?
Reacting with bromine water which changes from orange to colourless
76
How can vegetable oils that are unsaturated be hardened?
React them with hydrogen, pass over a nickel catalyst and heat at 60°C
77
What are hydrogenated oils?
Hydrogenated oils are vegetable oils that have extra hydrogen in them, making them harder
78
Why are hydrogenated oils useful?
They have a higher melting point and so are solid at room temperature, making them useful as spreads (cakes and pastries)
79
What is thermal decomposition?
The breaking up of a molecule using heat
80
What is a monomer?
What is a polymer?
Monomer – single molecule of a chemical such as ethane
Polymer – more than one monomer joined together such as poly(ethane)
81
What conditions are needed to make ethanol?
Ethanol can also be made by fermenting yeast – what is the equation for this?
Steam and a catalyst
Glucose → Carbon dioxide + Ethanol
82
What conditions are needed for hydrogenation?
React them with hydrogen, pass over a nickel catalyst and heat at 60°C
83
Give some examples of emulsions
Mayonnaise, milk, ice cream, salad dressing etc…
84
What are the benefits, drawbacks and risks of using vegetable oil to make fuel?
Advantages: carbon emissions reduced; better for the car; readily available
Disadvantages: specialist equipment needed; unknown risks
85
What are the issues associated with disposing of polymers?
Polymers are not biodegradable and so are difficult to dispose of
86
What raw material is used to make plastics?
Crude oil
87
What is fractional distillation?
A way to separate a mixture into different fractions, based on boiling point
Different hydrocarbons evaporate at different temperatures, after which they are condensed
88
Where is a fractional distillation column the coolest?
It is coolest at the top
89
Why is cornstarch used as a replacement for some previous polymers?
It is a biodegradable polymer which breaks down more easily
90
Why can combustion be termed as an oxidation reaction?
Combustion involves oxygen being added to the fuel (the carbon and hydrogen are oxidised)
91
What causes incomplete combustion
A lack of oxygen
92
What potentially dangerous gases are released in the combustion of fossil fuels?
Carbon dioxide / monoxide / sulfur dioxides / nitrogen oxides / un-burnt hydrocarbons / particulates
93
Why was Wegener’s continental drift theory not accepted for some time?
Continental drift was not accepted for a long time as it was thought the world was shrinking
94
What does the Earth consist of?
Crust, mantle, outer core, and inner core
95
How did scientists originally think mountains were formed?
Scientists believed that the shrinking of the Earth as it cooled caused the mountains
96
What are tectonic plates?
The Earth’s crust and upper part of the mantle is cracked into a number of large pieces, known as tectonic plates
97
What causes the tectonic plates to move?
Convection currents cause the movements of the tectonic plates
98
What causes the convection currents?
Natural radioactive processes release heat
99
What can happen if the tectonic plates move?
Earthquakes and volcanoes
100
How do earthquakes occur?
Earthquakes are causes by tectonic plates rubbing against one another
101
How long have the proportions of gases in the atmosphere been as they are?
200 million years
102
What gases are in the atmosphere?
Nitrogen, oxygen, carbon dioxide, noble gases, and water vapour
103
What are the proportions of the gases in the atmosphere?
78% nitrogen
21% oxygen
0. 04% carbon dioxide
0. 9% argon
+ small amounts water vapour + noble gases
104
What is distillation?
Distillation is when the solution is boiled and the vapour is cooled and collected
105
What chemicals can be used to identify double carbon bonds?
Bromine and iodine
106
How do materials biodegrade?
If materials biodegrade they are broken down by microorganisms
107
What happened on Earth in the first one billion years?
Violent volcanic activity
108
How did the oceans form?
The water vapour from the volcanic activity condensed and formed the oceans
109
What was the Earth’s early atmosphere mainly made of?
Mainly carbon dioxide with little or no oxygen
110
Which planets are similar to Earth’s early atmosphere?
Mars and Venus
111
What was there very little of in the early atmosphere?
Oxygen
112
What were there small amounts of in the early atmosphere?
Methane and water vapour
113
What produces oxygen?
Plants
114
How has the carbon from carbon dioxide been ‘locked up’?
Most of the carbon dioxide is locked up in sedimentary rocks as carbonates and fossil fuels
115
How do levels of carbon dioxide rise today?
Burning fossil fuels
116
Why is the burning of fossil fuels bad environmentally?
Carbon dioxide is thought to be responsible for climate change
Sulfur dioxide and oxides of nitrogen cause acid rain
Solid particles cause global dimming
117
What impact do humans have on the Earth?
Humans burn fossil fuels making carbon dioxide
Plastics are difficult to dispose of properly
118
What foods contain hydrogenated oils and why?
Margarine – this hardens the vegetable oil, turning it more solid so it can be spread
119
Why are long hydrocarbon chains ‘cracked’?
Long hydrocarbon chains are not as useful as short hydrocarbon chains so they are ‘cracked’ into smaller chains
120
What do cars have to reduce carbon monoxide, nitrogen oxides and un-burnt hydrocarbons?
Catalytic converters
Carbon Monoxide + Nitrogen Oxide → Nitrogen + Carbon Dioxide
Nitrogen Oxides → Nitrogen + Oxygen
Hydrocarbon + Oxygen → Carbon Dioxide + Water
121
What alternatives are there to fossil fuels?
Hydrogen (although requires energy to split in the first place) and bio-fuels (controversy growing plants for fuel when land could be used for food)
122
What is the Miler and Urey experiment of 1952?
An experiment to recreate life replicating the early conditions on Earth (ammonia, methane, hydrogen, water and electrical sparks simulating lightning)
Carbon compounds had formed (amino acids) which make proteins suggesting this is how life began (bacteria)
123
Crude oil is a mixture – what is a mixture
2 or more elements or compounds which are not chemically joined
124
What is the formula for methane, ethane, propane and butane?
Methane – CH4
Ethane – C2H6
Propane – C3H8
Butane – C4H10
125
How do the properties of long and short chain hydrocarbons differ in terms of boiling point, viscosity and flammability?
As hydrocarbon length increases the boiling point increases, the hydrocarbon becomes more viscous and less flammable
126
What is the formula for ethene and how would polyethene be represented?
Ethene – C2H4
127
What are the advantages and disadvantages of cooking in oil rather than in water?
Advantages: vegetable oils have higher boiling points than water so can be used to cook foods at higher temperatures producing quicker cooking
Disadvantages: cooking in oil increases the energy the food releases when eaten
128
How can sulfur dioxide gas released during the burning of fossil fuels be prevented?
Sulfur can be removed before burning as well as sulfur dioxide being removed after combustion
