Chemistry unit 2 AQA GCSE

Pregunta	Respuesta
What are compounds?	Atoms of two or more elements are chemically combined
Which two processes may chemical bonding involve?	Transferring or sharing
What does transferring electrons involve?	Lose electrons become positively charged
What do ions have the same electronic structure as?	Noble gases
What do alkali metals (group 1) react with to form ionic compounds?	Non metal elements
What do halogens (group 7) react with to form ionic compounds?	Alkali metals
What charge do halide ions have?	A single negative charge
What is an ionic compound?	A giant structure of ions
How are ionic compounds held together?	By electrostatic forces between oppositely charged ions (forces act in all directions) this is ionic bonding
When atoms share pairs of electrons which type of bonding is it?	Covalent bonding
What are giant covalent structures known as?	Macromolecules
What do metals consist of?	Giant structures of atoms arranged in a regular pattern
What happens to the electrons in the highest energy shell of metal atoms?	They are delocalised and are free to move through the whole structure
What are there electrostatic forces between?	Positive ions and the delocalised electrons
What do metals conduct and why?	Heat and electricity because of the delocalised electrons
Why can metals be bent and shaped?	The layers of atoms in metals are able to slide over each other
What are alloys?	A metal mixed with one or more other elements
What do the different sized atoms do to alloys?	Distorts the layers in the structure so it's difficult to slide over so are harder than normal metals
What can shape memory alloys do?	Return to their original shape after being deformed
What does nano science refer to?	Structures between 1-100nanometres
Why may nano science lead to the development of new catalysts or computers?	They show different properties to the same material in bulk with high SA:V
What are thermosetting polymers?	Polymer chains with cross links between them so they don't melt when heated
What are thermosoftening polymers?	Consist of individual tangled polymer chains
What do the properties of polymers depend on?	What they are made from and the conditions where they are made
Hats the difference between high and low density polymers?	High has chains close together
What are substances that consist of simple molecules?	Gases, liquids or solids that have relatively low boiling and melting points
Why don't simple molecules conduct electricity?	Because they have no overall charge
What are the weak forces between simple molecules called?	Intermolecular forces
When melted what can ionic compounds do?	Conduct electricity ions free to move
In diamond how many carbons are each carbon covalent lay bonded with?	Four so it's very hard
In graphite how many carbons is each carbon covalent key bonded with?	3
Why is graphite soft and slippery?	Because there are no covalent bonds between layers
Why can graphite conduct electricity?	One electron from each carbon is delocalised
What are fullerenes?	Carbon with different numbers of carbon atoms
Want are fullerenes used for?	Drug delivery in the body, lubricants, catalysts and nano particles for reinforcing materials
What can atoms that share electrons form?	Giant structures or macromolecules
What do macromolecules structures have?	High melting points and strong covalent points
What structure do ionic compounds have?	Regular structures with high electrostatic forces in all directions so it takes large amounts of energy to break bonds
What are isotopes?	Atoms of the same element that have different numbers of neutrons
How can artificial colours be detected?	Paper chromatography
What is a mass spectrometer?	Gives the molecular mass of each of the substances separated in the column
3 reasons why the predicted amount if product was not formed?	Because it's reversible, some reactants may react in ways different from expected and products lost when reaction mixture seperated
What does gas chromatography do?	Allows the separation of a mixture if compounds which travel through the column at different speeds the output is linked to a mass spectrometer
when do chemical reactions occur?	When particles collide with the activation energy needed
What are five things that increase the rate of the reaction?	Temperature, concentration, pressure, surface area and catalysts
What happens when chemical reactions occur?	Energy is transferred to the surroundings
What does an exothermic reaction do?	Transfers energy to the surroundings
What does an endothermic reaction do?	It takes in energy from the surroundings
If a reversible reaction is exothermic in the forward direction what is it in the backwards direction?	It is endothermic
What are two examples of bases?	Metal oxides and hydroxides
Salt solutions can be crystallised to produce what?	Solid salts
Which ions make a solution acidic?	H+
Which ions make a solution alkaline?	OH-
Ammonium dissolves in solution to form what type of solution?	An alkaline solution to produce ammonium salts
What can ammonium salts be used for?	fertilisers
What three things can acids be reacted with to make salts?	Bases, carbonates and metals
What two things does the type of salt produced depend on?	The acid used and the metal in the base or alkali
What is another way salts can be formed?	By mixing appropriate solutions of ions so that a precipitate is formed
During electrolysis what happens to positive ions?	they move towards the negative electrode and go through reduction
What two things can electrolysis be used for?	to electroplate objects and break down a solution into elements
What is an electrolyte?	The substance broken down by electrolysis
what does the product formed depend on in electrolysis?	Its reactivity
What is aluminium manufactured from?	Cryolite and aluminium oxide
Where does aluminium form in electrolysis?	at the negative electrode and oxygen at the negative electrode
What is the positive electrode made from in aluminium manufacturing?	carbon so CO2 is formed
What does the electrolysis of sodium chloride solution produce?	hydrogen and chlorine
What can sodium hydroxide be used for?	soap
What is chlorine from electrolysis of sodium chloride solution used for?	Bleach and plastics

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