Chemistry 2A

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  • Created by: JennD
  • Created on: 31-05-17 20:03
What is the mass number?
The number of protons and neutrons
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What is the atmoic number?
Number of protons/electrons
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Protons mass
1
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Neutrons mass
1
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Electron mass
Very very small
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Number of neutrons=
Mass Number - Atomic Number
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What are compounds?
When two or more atoms are chemically bonded together
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Is it difficult to seperate chemically bonded compounds?
Yes. It is almost impossible
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What are isotopes?
Different atomic forms of the same element, whihc have the same number of protons but a different number of neutrons
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Give a common set of isotopes
C-12 and C-14
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Are isotopes the same or different elements?
Different
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What is ionc bonding?
Where the metal loses electrons gaining postive ions and the non-metal gain ions forming negative ions. The opposite charges then attract
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Why are atoms in group 1 and 2 so reactive?
There shells are very un-full meaning they want to react with anything to fill their outer shells
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Why are atoms in group 6 or 7 so unreactive?
Their outer shells are almost full meaning they do not need to readt as much to fill their outer shells
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What structure do ionic compounds have?
A regular lattice. The ions are closely packed together and a regualr arrangment. They have very strong forces of attraction between oppositely charged ions in all directions.
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Do ionic cimpounds have similar or different properties
Similar
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What properties do ionic compounds have?
Have high melthing points and high boiling points due to strong forces of attraction in the ions. Large amount of energy are needed to do this. When melting occurs the ions are free to move meaning they are able conduct a current
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What happens when ionic compounds dissolve in water?
The ions seperarte causing them to be free to move in the solution. This allows them to carry an electric current
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What is the overal charge of any compound?
0
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What is covalent bonding?
This occurs in 2 non-metals and it is where electrons from the outer shells are shared to make a full shell of electrons
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What are the 2 forms of covalent structures?
Simple molecular strucutures and giant covalent structures
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What is the structure of a simple molecular covalent bond?
The atoms form strong bonds forming small molecules or several atoms. The forces of attraction is very weak
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What are the properties of a simple molecular covalent bonds?
They have low melting and boiling points due to weak forces of attraction
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Why do covalnet bonds or molecular substances not conduct electricity?
There are no ions meaning there is no electrical charge
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What is the name for giant covalent structures?
Macromolecules
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What is the difference between giant covalent bonds and giant ionic bonds?
There is no charge in giant covalent structures as there are no ions
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What is the structure of macromolecules?
They are bonded with strong covalent bonds
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What are the properties of macromolecules?
They have very high melting and boiling points. They don't conduct electricity- not even when molten
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Name 2 atoms that are macromolecules and conduct electricity
Carbon and Silicon dioxide
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What is the strcutre of dimonds?
Each carbon atom have 4 covalent bonds and it is very rigid. This makes dimonds extremely hard (hardest on earth, which is why it is used for drill tips) They are sparkly too
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What is the structure of silicon dioxide (silica)?
This is what sand is made of. Each grain of sand is one giant structure of silicon and oxide
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What is the strucutre of graphite?
They only form 3 covalent bonds, which creates layers allowing them to slide over each other. Carbon has delocalised electrons allowing it to conduct electricity. The loose layers can be rubbed off. How a pencil works
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What structures do metals have?
Have giant structures
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Why are metals good conductors of electricity and heat?
They have delocalised in their outer shell
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What is a metals structure?
The electrons are held together in a regular structure. There are strong forces of attraction between positive and negative electrons. The layers of atoms slide ovr each other
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Why are metals bendy and easy to shape?
They layers can slide over each other
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What are alloys?
This is where different sixed atoms are added to the regular arrangement breaking it. This makes the alloys harder as the layers can't slide over each other
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What are the 4 forms of structures?
Giant ionic, simple molecular, giant covalent and giant metallic
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What structure has a low melting and boiling point. It is also not a good conductor. What is it?
Simple molecular
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What structure has a high melthing and boiling point. It is also a good conductor. What is it?
Giant metallic
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It has a really high boiling point and is not a good conductor. What is it?
Giant covalent
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It has a quite low melting and boiling point and is a good conductor when molten. What is it?
Giant ionic
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What are smart materials?
They are materials that have really wierd properties depending on the conditions e.g. temperature
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State the properties of nitinol?
It is an alloy. When it's cool you can bend it and twist it. If you heat it to a certain temperature it goes back to it's original shape
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What 2 things is nithinol used for?
Glass frames (if you accidently bend them and put them into hot water they go back to their normal shape) and dental braces as they gentally pull your face when they are warmed in your mouth
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What are nano particles?
They are really tiny about 1-100 nanometers. They contain roughly a hundred atoms
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What do nano-particles contain?
Fullerenes. These are carbon molecules shaped like hollow balls or closed tubes. They are arranged in hexagonal tings
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What is the science called when you use nanoparticles?
Nanoscience
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Name 3 nanopartilces that are being developed
Industrial catalysts due to their large surface area to volume ratio, sensors to detect single molecules and nanotubes as these are stronger and lighter for building material
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What 2 things determine the properties of a polymer?
Weak forces of attraction and strong forces of attraction
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What properties do weak forces of attraction make polymers?
Have weak intermolecular forces. They are able to freely slide over each other
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What properties do strong forces of attraction make polymers?
Have stronger intermolecular forces between polymer chains (crosslinks) allowing the chians to be held together firmly
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What are thermosoftening polymers?
These don't have cross-linking between chains meaning forces are really easy to overcome causing them to be easy to melt. When it cools the polymer hardens forming a new shape. You can remould these plastics when you like
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What are thermosetting polymers?
These have crosslinks meaning the chains hold the solid structure together. The polymer doesn't soften when heated. They are also strong, hard and rigid
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State 2 types of polyethene that can be made using different conditions
Low density polythene and High density polythene
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Low denisty plothene properties
Made from heating ethene to about 200C under high pressure. Its flexible so it used for bottles and bags
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High density plothene properties
Made a low temperatures with pressure and a catalyst. These are rigid and are used for water tanks and drainpipes
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State 3 properites that a plastic depends on for its use?
Cost, resistance to chemicals and metling point
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What is the relative mass?
How heavy something is
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What is the relative mass number the same as?
The mass number of the element (the bigger of the 2 numbers in a periodic table)
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What is one mole equal to?
The relative mass formula in grams
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Formula for the number of moles
Mass in g (of element or compound) / Relative formula mass (of element or compound)
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Percentage mass of an element or compound formula
(Relative atomic mass x number of atoms / the relative mass formula) x 100
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What are the 5 stages of the empirical formula?
List all the elements in the compound, underneath them writer their experimental masses or percentages, divide each mass or percentage by the A, turn the numbers you get into a ratio and then turn the ratio into the simplest formula
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What are the 3 stages to calculating masses in eactions
Write out the balanced equation, work out the relative mass formula for the 2 bits you want and apply the rule: divide to get one then multiple to get all
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Percentage yeild formula
(Actual yield (grams) / predicted yield (grams)) x 100
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How can colours be seperated?
Chromatography
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How do you conduct a chromatography expriment?
Extract the colour from the food sample by placing it in a cup and adding a few drops of solvent. Put spots of this colour on a pencil line (pencil doesn't run) rul the sheet up and place it in a beaker with some solvent and watch the colours run
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What are the advantages of using machines for chromatography?
Very sensitive (detect tiny amounts of substances), very fast and very accurate
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What is gas chromatography used for?
Allows you to identify gases present in compounds
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How does gas chromatography work?
The gas is carried in a column packed with a solid material, as the gases travel at different speeds they seperate and are then detected by a machine. The time they take to be detected is their rection time
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In a gas chromatography graph what do the peaks show?
How many compounds are present in the sample
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What does the postion of peaks show in a gas chromatography graph?
The retention time
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What is the process called when a gas chromatography column is linked to a mass spectrometer?
CG-MS
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What does a CG-MS identify?
The substances leaving the column very accurately
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How can you work out the relative molecular mass of each of the substances from the graph?
Read of the molecular ion peak
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Other cards in this set

Card 2

Front

What is the atmoic number?

Back

Number of protons/electrons

Card 3

Front

Protons mass

Back

Preview of the front of card 3

Card 4

Front

Neutrons mass

Back

Preview of the front of card 4

Card 5

Front

Electron mass

Back

Preview of the front of card 5
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