Additional Science Unit 2: Chemistry

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What is the relative mass of a proton?
1
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What is the relative mass of a neutron?
1
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What is the relative mass of an electron?
Very small
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What is an isotope?
Atoms of the same element that have the same number of protons but a different number of neutrons
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What is an Ionic bond?
Atoms lose of gains electrons to form positive or negative ions. Oppositely charged ions are attracted to each other to form ionic bonds.
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How do you draw an ionic bond between Sodium and Chlorine (NaCl)?
.
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How do you draw an ionic bond between Magnesium and Oxygen (MgO)?
.
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How do you draw an ionic bond between Calcium and Chlorine (CaCl )?
.
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What are the properties of ionic compounds?
.
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What structure do ionic compounds have?
Giant ionic lattice. Oppositely charged ions are attracted to each other in all directions.
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In ionic bonding, what does the group number in the periodic table tell us?
The charge on the ion formed.
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What is a covalent bond?
A shared pair of electrons between two atoms to allow each atom to have a full outer shell. Electronic structure of a noble gas
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How do you draw a covalent bond between Hydrogen (H )?
.
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How do you draw a covalent bond between Chlorine (Cl )?
.
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How do you draw a covalent bond between Methane (CH )?
.
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How do you draw a covalent bond between Hydrogen Chloride (HCl)?
.
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How do you draw a covalent bond between Ammonia (NH )?
.
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How do you draw a covalent bond between water (H O)?
.
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How do you draw a covalent bond between Oxygen (O )?
.
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What are the characteristics of Diamond?
Giant covalent lattice. Very high melting/boiling point, dont conduct electricity, carbon forms four covalent bonds held tightly, very hard substance.
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What are the characteristics of Silicon Dioxide (Silica)?
Giant covalent lattice structure. Very high melting/boiling point, dont conduct electricity.
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What are the characteristics of Graphite?
Giant covalent lattice structure. Very high melting/boiling point, carbon atoms form three covalent bonds, creates layers that are free to slide over each other, makes it soft and slippery, conducts electricity.
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What is a compound?
Substances in which atoms of two or more elements are chemically combined
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What types of material does ionic bonding take place in?
A metal and a non-metal
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What are the properties of metals?
Giant structures, atoms arranged in a regular pattern, layers can slide over each other meaning they can be bent and shaped
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What is an alloy?
Two or more different metals mixed together.
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Why do alloys have different properties to its metals?
Different metals have different sized atoms. When mixed together it cant form layers so its harder for the layers to slide over each other. So alloys are harder.
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Give an example of a new material with unique properties
Nitinol - shape memory alloy. Can be bent and twisted when cool but when heated returns to a remembered shape. Used in dental braces.
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What are the properties of nanoparticles?
Tiny particles (1 - 100 nanometres), contain a few hundred atoms, huge surface area compared to volume.
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What are the uses of nanoparticles?
Catalysts (big surface area), sensors that can only detect one thing, stronger/lighter building materials, new cosmetics, new lubricant coatings that reduce friction, tiny electric circuit for computer chips.
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What are the properties of simple molecules (eg, water, oxygen)?
Relatively low melting/boiling points, dont conduct electricity (no overall electric charge)
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In what state can ionic compounds conduct electricity and why?
When melted (molten) or dissolved in water. The ions are free to move and carry the current.
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Explain a "thermosoftening" polymer.
Made up of tangled chains of polymers that can slide over each other. Easy to melt, remouldable
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Explain a "thermosetting" polymer.
Made up of straight chains of polymers that have crosslinks between them, these hold the chains in a solid structure. Dont melt when heated, fixed once shaped.
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What is Low Density (LD) Polythene used for and why?
Used for plastic bags and bottles as it is flexible
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What is High Density (HD) Polythene used for and why?
Used for water tanks and drainpipes and it is stiffer.
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What does a polymers properties depend on?
Depends on the materials it is made from and the reaction conditions (eg. temperature, pressure, catalyst etc)
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How do you calculate the Relative Formula Mass (Mr)?
You add up the Relative Atomic Mass (Ar) of the elements present.
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What is one mole of an element?
The relative formula mass (Mr) or relative atomic mass (Ar) of a substance in grams.
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How do you calculate the percent mass of an element in a compound?
.
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What is the percentage yield of a reaction?
The percentage of useful product you get from a reaction, always lower than expected.
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Why is the yield never 100%?
The reaction is reversible, some product may be lost when its separated from the reaction mixture, other unexpected reactions may be happening
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Why is the yield calculation important for sustainable development?
It helps us to make sure that we dont use resources faster than we can replace them so that we dont run out.
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What should we aim to do to help with sustainable development?
use as little energy as possible, use as few reactants as possible, get the highest yield possible.
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What is paper chromatography used for?
To see what dyes are contained within one colouring
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How does paper chromatography work?
The different coloured dyes travel up the paper at and spread out so that you can see which dyes make up the colouring.
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What are the advantages of instrumental methods?
Very sensitive (only need small sample), Very fast, Very accurate
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What is gas chromatography used for?
Can separate out a mixture of compounds and help identify them.
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How does gas chromatography work?
The substances travel through the column at separate speeds so are separated. The recorder draws a graph to with peaks to show the different substances.
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What is retention time?
The time it takes for a substance to pass through a gas chromatography machine. Each substance has a different retention time.
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How can you improve an experiment that uses gas chromatography?
It can be linked to a mass spectrometer which can be used to help identify the substances leaving the column very quickly and very accurately. It can also detect very small amounts.
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What does the rate of a reaction depend on?
Temperature, concentration, pressure, surface area and presence of a catalyst.
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On a graph, how can you tell which reaction is fastest?
The graph with the steepest slope
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How can you measure the rate of a reaction?
How quickly the reactants are used up or how quickly the products are formed
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How do you calculate the rate of a reaction?
.
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Explain how to use precipitation to determine the rate of a reaction
The product of a reaction is a (precipitate) solid which makes a solution cloudy. The quicker this precipitate is formed, the faster the reaction.
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Explain how to use a change in mass to determine the rate of a reaction.
If the product in a reaction is a gas then the mass of the solution will go down as the gas is given off. The faster the mass goes down, the faster the reaction.
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Explain how to use the volume of gas given off to determine the rate of reaction.
Use a gas syringe to measure the gas given off over a set time. The more gas given off in that time, the faster the reaction
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How does a larger surface area affect the rate of a reaction and collisions?
Faster rate of reaction, more area for other particles to collide with so will collide more often.
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How does a higher concentration affect the rate of reaction and collisions?
Faster rate of reaction, more particles of reactants present so will collide more often.
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How does a higher temperature affect the rate of reaction and collisions?
Faster rate of reaction, the particles with are moving faster so will collide more often.
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How does the presence of a catalyst affect the rate of reaction?
Faster rate of reaction
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What is a catalyst?
A substance which speeds up a reaction without being used up. Different reactions need different catalysts
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How do collisions affect the rate of a reaction?
The faster the collisions occur, the more energy the collisions will have so the more successful they will be so the reaction rate will be faster.
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What are the advantages of using catalysts in industry?
Takes less time to do the reactions, saves money, allows reaction to be done at lower temperature, uses less energy, can be used more than once
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What are the disadvantages of using catalysts in industry?
Can be expensive to buy, need to be removed and cleaned, can be "poisoned" by other substances so they stop working.
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What is the activation energy?
The minimum amount of energy particles need to have to react.
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What is an exothermic reaction?
A reaction that gives out energy to the surroundings (eg. cause a rise in temperature). Common examples: combustion, neutralisation, oxidation
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What is an endothermic reaction?
A reaction that takes in energy from the surroundings (eg. cause a fall in temperature). Common example: Thermal decomposition
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If a reversible reaction is endothermic one way, what is it the other way?
Exothermic
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What is the reversible reaction involving copper sulfate (II)?
Hydrated copper sulfate ==== anhydrous copper sulfate + water
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What does the state symbol (s) stand for?
Solid
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What does the state symbol (l) stand for?
Liquid
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What does the state symbol (g) stand for?
Gas
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What does the state symbol (aq) stand for?
Aqueous - dissolved in water
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What are the two equations that show a neutralisation reaction?
.
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What ions make a solution acidic or alkaline?
H+ ions make it acidic, OH- ions make it alkaline
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How can soluble salts be made? Reacting acids with...
Metals (not all metals are suitable), insoluble bases and alkalis.
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Why would you crystallise a salt solution?
To produce a solid salt
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How do you make an insoluble salt? What is it used for?
Mixing appropriate ions until a precipitate is formed. Used to remove unwanted ions from solutions (eg. treating drinking water)
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How do you determine what base salt is made from an acid and base?
Depends on acid used and metal used in the base
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What metals are classed as bases?
Metal oxides and metal hydroxides
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What is so important about ammonia?
Ammonia dissolves in water to make an alkaline solution, it can be used to produce ammonium salts which are important as fertilisers.
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How is aluminium manufactured?
By the electrolysis of molten aluminium oxide and cryolite. Aluminium forms at the negative electrode and oxygen forms at the negative electrode.
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What is cryolite and why is it used?
Cryolite acts as a catalyst in the electrolysis of aluminium. It lowers the temperature needed to make the aluminium oxide molten and makes the whole process cheaper
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Why is the electrolysis of sodium chloride solution important in the chemical industry?
It forms hydrogen, chlorine (used to make bleach and plastics) and sodium hydroxide (used to make soap).
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