CHEMISTRY EXAM (Full GCSE) Flashcards
What elements form part in an ionic bond?
Metals + Non-Metals
What elements form part in covalent bonding?
Non-metals + Non-metals
What elements form part of metallic bonding?
Metals + Metals
What’s an ionic bond?
Electrostatic force of attraction:
- Strong bonds
- Soluble in water
- Can’t conduct electricity in solid, only in liquid
What’s a covalent bond?
Held together by electrostatic attraction
- A shared pair of electrons
What’s an allotrope of carbon?
Giant covalent structures out of carbon
- Same chemical properties
- Different physical properties
What’s a metallic bond?
Metal + Metal
- Complete full outer shell
- Metal ions and sea of electrons held together
What’re the properties of metals?
- High boiling/melting points
- Good conductors of heat/electricity
- Malleable & Ductile
What’s chromatography?
Technique for separating components in water soluble mixtures.
What’s the mobile & stationary phase in chromatography?
Mobile: Water
Stationary: Paper
What’s Rf (Chromatography)?
Percentage (/1) of distance to solvent front
What’s a nanoparticle?
A particle with the size of 1-100 nanometres
- High surface area to volume ratio
When 2 elements join the end is?
IDE
When 3+ elements join & one of them is oxygen the ending is?
ATE
What’s a half equation?
Model for change in reactant in a reaction
- Involves charges
- Shows electron movements
What’s an ionic equation?
Symbol equation but showing changes in charge of substances
- Spectator ions are NOT involved in the reactions
What’s a mole?
Measurement for the amount of a substance
- 6.02 x 10^23 particles
- Moles = mass/Mr
What’s empirical formula?
Simplification of molecular formula
What’s an exothermic reaction?
Reaction that takes in less energy than it gives out.
What’s an endothermic reaction?
A reaction that takes in more energy than it gives out.
What’s a reaction profile?
Model for energy in a reaction
- Activation Energy: Energy needed to start a reaction
How do you calculate energy change?
- Count the number of bonds
- Multiple by their energy
- Then EA = endothermic-exothermic
What’s a redox reaction?
Reactions where oxidation and reduction take place.
What’s oxidation & oxidizing agent?
Oxidation: Gain of oxygen or loss of electrons
Oxidising Agent: Substance that removes electrons from other substances
What’s reduction and reducing agents?
Reduction: Removal of oxygen or gain of electrons
Reducing Agent: Substance that can give electrons to other substances
What’s an acid?
Contain hydrogen in formulae, substance which releases Hydrogen ions when dissolved in water.
What’s a base?
- Opposite to acids
- Contain elements that react with acids to make water
What’s an alkali?
Bases that make OH- ions
- Neutralisation with acids
Neutralisation word equation?
Acid + Alkali –> Salt + water
Acid carbonate reaction word equation?
Acid + Carbonate –> Salt + water + carbon dioxide
Metal acid reaction word equation?
Metal + Acid –> Salt + Hydrogen
Strong/weak acids classification?
Classification of acids depend on how much they ionise the water
What’s a dilute acid?
Contains low ratio of acid to solution
What’s a concentrated acid?
Contain high ratio of acid to solution
What’s electrolysis?
Splitting up substances with electricity
What happens at the Anode?
Anode (+):
- Attracts negative ions
- Lose electrons to become atoms
What happens at the Cathode?
Cathode (-):
- Attracts positive ions (metals)
- Gains electrons to become atoms
Rules for anode:
- If ions are halides, then the halogen is produced
- If ions aren’t halides, then oxygen is produced
Rules for cathode:
- If metal ions are more reactive than hydrogen, then hydrogen is produced
- If metal ions are less reactive than hydrogen, then the metal is produced
What’s electroplating?
- Technique where object is coated with a metal
How does electroplating work?
- Coating metal is an anode and electrolyte containing coating metal
- Coating metal gets separated and attracted to object (cathode) where it coats the object
- Coating metal (anode), loses electrons and ions dissolve in solution
- Can also be used to purify copper (with a sample of pure copper)
What’s an isotope?
Different forms of the same element:
- Same number of protons
- Different number of neutrons
What’re simple molecules?
Molecules with covalent bonds
- Low melting/boiling points
- Covalent bonds are strong
- Bonds between molecules are weak
- Don’t conduct electricty
What’s a polymer?
Lots of molecules (monomers join together).
- This is polymerisation (needs high pressure and catalyst)
- Plastics are polymers
What’s an alloy, why is it used?
- Mixing metals with other elements make alloys
- Used to change its properties
What does pure mean?
- Made up of a single element
How does simple distillation work?
- Separates liquids from solutions
- Can only be used to separate things with very different boiling points
What’s fractional distillation?
- Used to separate mixture of liquids
- Uses different boiling points to seperate liquids
What’s filtration?
Filtration is used to separate an insoluble solid from a liquid
- Uses filter paper, and only water can get through
What’s crystallization?
Separates soluble solids from a solution
What’s the solvent?
Substance that dissolves a solute
What’s a solute?
Substance that dissolves in a solvent, forming a solution?
What’re the different state symbols?
(s): Solid
(l): Liquid
(g): Gas
(aq): Aqueous
What’re alkali metals?
Group 1:-
- Low melting/boiling points
- High density
How does reactivity change in alkali metals?
Gets more reactive as you go down the group.
- As it’s further away and you need to lose it
- so less energy is needed to to remove it
What’re halogens?
Group 7:
- Diatomic
- As you go downt he group, melting/boiling points increase
How does reactivity change going down halogens?
As you go down the group, the reactivity decreases.
- This is because it needs to gain an electron
- And further down it has more shells
- So more energy is needed to gain the electron as it’s further from nucleus
What’re noble gases?
- Very unreactive (full outer shells)
- Colourless
- Monatomic
What’re transition metals?
Metals in the middle of periodic table:
- Good conductors of heat/electricity
- High density, melting points, malleability & ductility
- Harder but less reactive than alkali metals
- Reactive decreases from left to right
How can you test for carbon dioxide?
- Bubbling it through limewater
- Will turn cloudly
How do you test for hydrogen?
Squeaky Pop Test:
- Makes a pop with a lighted splint
How can you test for oxygen?
- Glowing splint
- Will light if there’s oxygen
How can you test for chlorine?
Use litmus paper
- If gas is chlorine, it will bleach litmus paper
How do you draw covalent bonds?
- Dots & Crosses diagrams
What’s an ion?
An ion is a charged particle or molecule due to a gain or loss of an electron.
First three shells?
2,8,8
Wha’re polymers?
Long chain molecules (monomers).
What’s polymerization?
The formation of polymers with high pressure & catalyst.
Force strength of intermolecular forces?
Weak.
Force strength of covalent bonds?
Strong.
Force strength of ionic bonds?
Strong.
What causes strong metallic bonding?
Strong attraction between delocalized electrons & positive ions.
what did the gold foil experiment show?
Some alpha particles were deflected, and a small percentage bounced back.
What did the gold foil experiment prove?
That the atom was mostly empty.
With a positive nucleus.
What’re giant covalent structures?
Lots of covalent bonds hold atoms together.
Properties of giant covalent structures?
- High melting points
- Can’t conduct electricity
- Strong bonds
Examples of giant covalent structures?
- Diamond
- Graphite & Graphene
- Fullerenes
Why do ionic compounds only conduct electricity when molten?
Because when it’s solid, ions can’t move.
But when molten, ions can move and carry an electrical current.
Why do simple molecules not conduct electricity?
Because there aren’t any free electrons or ions.
Why do simple molecules have low melting/boiling points?
Atoms have strong covalent forces.
But the forces that hold the molecules together are very weak, so it takes low energy to break them.
Carbonate ion charge?
2-
Sulfate ion charge?
2-
Hydroxide ion charge?
1-
Oxide ion charge?
2-
Nitrate ion charge?
1-
What’s ammonia?
NH3
What’s a symbol equation?
Equation that shows symbols of reactants and products, with the amount of each thing.
What’re state symbols?
Tell you the state of a substance in an equation?
What’re half equations?
Show how electrons are transferred during reactions.
When can you use half equations?
Only in redox reactions.
What’s a mole number?
6.022 x 10^23
Moles equation?
Moles = Mass / Mr
What’s exothermic & endothermic?
Exothermic: Gives out more energy than it takes in.
Endothermic: Takes in more energy than it gives out.
What’s a reaction profile?
Graph that shows energy levels of the reactants & products in a reaction.
What’s activation energy?
Minimum amnount of energy needed for bonds to break and start a reaction?
Breaking bonds takes in or gives out energy?
Takes in energy
Forming bonds takes in or gives out energy?
Gives out energy
Bond Energy Change equation?
Overall Energy Change = Energy to break bonds - Energy released by forming bonds
Acid + Metal –> ?
Acid + Metal —> Salt + Hydrogen
Acid + Metal Carbonate –> ?
Acid + Metal Carbonate —> Salt + Water + Carbon dioxide
Acid + Alkali –> ?
Acid + Alkali –> Salt + Water
How does electrolysis work?
1) Current decomposes electrolyte
2) Cations (+) & Anions (-) go to Cathode & Anode respectively.
3) Cations (+) gain electrons (reduction)
4) Anions (-) lose electrons (oxidation)
5) This makes substances become uncharged
What does molten ionic produce in electrodes?
Cathode (-): Metal atoms
Anode (+): Negative ions become atoms.
What does aqueous solutions produce in electrodes?
Cathode: If metal more reactive than H than H is produced. Otherwise the metal is produced.
Anode: If Halide ions are present the halogen is produced, otherwise oxygen is produced.
How can you measure pH of a solution?
- Indicator
- pH probe
What’re 3 properties of ceramics?
- Insoluble
- Very Strong
- Do not react chemically
- Very brittle
- Easily moulded
What are group 1 elements?
Alkali metals
What do halogens react vigorously with?
Alkali metals
What is a halogen displacement reaction?
When halogens react with halides and the halogen displaces the less reactive halogen from the halide.
How do noble gases change going down the group?
- Boiling point increases as attractive forces between atoms gets stronger
- Density increases
What groups do transition metals occupy?
Groups 3-12
Word equation for Metal + water?
Metal + Water –> Metal hydroxide + Hydrogen
What’s a metal displacement reaction?
A more reactive metal displaces a less reactive metal from a solution.
What’s more reactive than carbon?
Lithium, Potassium, Barium, Calcium, Sodium, Magnesium & Aluminium
What’s less reactive than carbon but more reactive than hydrogen?
Zinc, Iron, Nickel, Tin & Lead
What’s less reactive than hydrogen?
Copper, Mercury, Silver, Gold & Platinum
How can you test for hydrogen?
Place a lighted splint in container, if it’s hydrogen it will ignite with a squeaky pop.
What is the flame test?
Heating metal ions produce a different colour depending on the ion.
What colour do lithium, sodium, potassium, calcium & copper turn in flame test?
Lithium (Li+): red
Sodium (Na+): yellow
Potassium (K+): lilac
Calcium: (Ca2+): orange-red
Copper (CU2+): green-blue
What colour of hydroxide precipitate do iron (ii), iron (iii), coper (ii), calcium & zinc produce?
Fe2+: green
Fe3+: orange-brown
Cu2+: blue
Ca2+: white
Zn2+: white
What’s instrumental method of analysis?
Uses machines to analyse substances.
Benefits of instrumental methods of analysis?
- Sensitivity
- Accuracy
- Speed
What’s the yield of the product?
Mass of the product made in a chemical process.
What’s the theoretical yield?
Maximum mass possible from a given mass of reactants.
How do you calculate theoretical yield?
- Calculate moles of limiting reactant (mass/Mr).
- Figure out moles of product through ratio
- Multiply by Mr of product and you get mass in grams
Percentage yield equation
percentage yield = (actual yield)/(theoretical yield) x 100
Why is percentage yield never 100%?
- Reactants might react with other substances to make new products
- Reaction might not be complete
- May loose product when you separate or collect it
- Reactants might not be pure
What’s atom economy?
Percentage of the product you want over the total mass (Mr) of products.
Atom economy equation?
Atom economy = (useful product)/(total mass of products) x 100
What’s a reaction pathway?
Reactions undertaken to make a particular substance.
What must be considered when deciding a reaction pathway?
- yield of product
- atom economy
- usefulness of by-products
- rate of reaction
What’s a litre equal to?
1 cubic decimetre (dm3)
Concentration equation mass
Concentration (g/dm3) = mass (g) / volume (dm3)
Concentration equation moles
Concentration (mol/dm3) = moles / volume (dm3)
What’s a titration?
Titration is a technique used to find the concentration of an acid or alkali through neutralization reaction.
Hoes does titrations work?
- Add a known volume of alkali to conical flask
- Then add acid from burette
- When it changes colour (indicator), reaction completed, neutralization
- Calculate titre
What’s a titre?
Volume of acid added to the alkali in the flask
How much volume does 1 mol of gas occupy at room temp & pressure (RTP)?
24dm3
What’s the molar volume?
Volume one mol of a gas occupies at RTP
How to calculate volume at RTP?
Volume = moles x 24dm3/mol
What’s rate of reaction?
How quickly reactants are used up, or products are formed.
What increases rate of reaction?
- Temperature
- Concentration
- Pressure
- Surface area
- Catalysts
What are reversible reactions?
Reaction goes both ways:
Reactants <–> Products
What is hydrated?
Contains water molecules
What is anhydrous?
Doesn’t contain water molecules
What’s the reversible reaction symbol?
⇌
What is dynamic equilibrium?
In a closed system, the reversible reactions moves both ways at the same rate.
What happens at dynamic equilibrium?
- Forward & Backward reaction will still happen, but at the same rate
- Concentrations of reacting substances are constant
What’s the equilibrium position?
Ratio of concentration of products to reactants?
What does it mean if the equilibrium position is to one side?
It means that one side has a higher concentration.
For example: left side means reactants have a higher concentration.
What happens when you increase the pressure in a reversible reaction?
- Equilibrium position moves to the side with least moles
- Reaction to side with least moles is favoured
What happens when you increase the concentration in a reversible reaction?
- Equilibrium position moves to the side with least concentration
- Reaction to side with least concentration is favoured
What happens if you increase the temperature in a reversible reaction?
- Endothermic reaction is favoured
What’s equilibrium yield?
Amount of desired product present in a reaction at equilibrium.
What are the compromises in temperature in reversible reactions?
- Temp might need to be low for high yield
- But at low temp, ROR is slow
- Compromise temp is used to balance
What are the compromises in pressure in reversible reactions?
- Pressure might need to be high for high yield
- But at high pressures, it’s expensive, requires lots of energy and tough vessels
- Compromise pressure is used to balance
What elements do plants need?
Nitrogen, phosphorus & potassium.
What do fertilizers do?
They replace the elements used by plants as they grow.
What’s the Haber process?
Produces ammonia from nitrogen and hydrogen.
Haber process equation
N2 + 3H2 ⇌ 2NH3
How are reactants produced in the Haber process?
Nitrogen: Fractional distillation of liquefied air
Hydrogen: Reacting natural gas with steam
What are the condition of the Haber process?
- Iron catalyst
- High temperature (450ºC)
- High pressure (200atm)
What’re the different industrial processs?
- Batch
- Continous
What’re the difference between batch & continuous processes?
Batch: Make a small amount at a time
Continous: Large amounts and go all the time
How is ammonia collected during the Haber processes?
- Gases in reaction vessel cooled, liquid ammonia collected.
- Nitrogen & Hydrogen recycled to continue making ammonia
What’s the contact process?
Process for making Sulfuric acid (for fertilizers) from sulfur, air & water.
What’s the first step? (Contact process)
Sulfur burn in air to produce sulfur dioxide
S + O2 –> SO2
What’s the second step? (Contact process)
Sulfur dioxide & oxygen react to produce sulfur trioxide
2SO2 + O2 ⇌ 2SO3
What’s the third step? (Contact process)
Sulfur trioxide reacts with water to make sulfuric acid.
H2O + SO3 –> H2SO4
What’re two ways of making ethanol?
- Fermentation
- Hydration of ethene
What’s an ore?
rock or mineral that contains extractable metal.
What’s malachite?
copper carbonate
What’s bauxite?
aluminium oxide
What’s hematite?
iron(III) oxide
How are metals extracted from ores?
More reactive than Carbon: Electrolysis
Less reactive than Carbon: Heating compounds with carbon
How can copper be extracted?
Stage 1: Roasted in air
2CuS + 3O2 –> 2CuO + 2SO2
Stage 2: Heated with carbon
2CuO + C –> 2Cu + CO2
How is iron extracted from its ore?
Using a blast furnace.
What’s Stage 1? (Blast furnace)
Coke burns in hot air
C + O2 –> CO2
What’s Stage 2? (Blast furnace)
Coke is added to CO2, making CO
C + CO2 –> 2CO
What’s Stage 3? (Blast furnace)
Carbon monoxide reduces iron oxide to produce iron
3CO + Fe2O3 –> 3CO2 + 2Fe
How is aluminium oxide electrolysed?
- Dissolved in cryolite to lower melting point
- Electrolysed at 950ºC
- Aluminium produced at the cathode
Why must the anodes be replaced when aluminium is electrolysed?
Because, oxygen (from Aluminium oxide) reacts with the anodes making CO2, deteriorating the anode.
What is bioleaching?
Bacteria which oxidise metal ions, to produce low grade ores.
What is phytoextraction?
Plants absorb metal ions, then they are burned and a high-grade ore ash is produced.
What are the benefits of bioleaching and phytoextraction? And drawbacks?
They are cheaper, produce less waste and use less energy.
But they are slow.
What’s an alloy?
Mixture of two or more elements (one is a metal.
Examples of alloys?
- Solder
- Brass
- Bronze
What is corrosion?
Reaction of a metal with substances in its surroundings.
What is rusting?
A type of corrosion when iron and steel react with water or oxygen.
Rusting of iron equation
iron + oxygen + water –> hydrated iron(III) oxide
How can you reduce rusting?
- Painting
- Coating with oil, grease, plastic
- Plating with zinc or tin
What is sacrificial protection?
Protecting iron/steel from corroding with a more reactive metal that corrodes first.
What is galvanizing?
Dipping object in molten zinc. This stops air/water eaching object and also acts as a protective layer.
What are composite materials?
Combination of 2+ materials with different properties. Composite material has different properties.
What’s a life-cycle assessment?
A ‘cradle-to-grave- analysis of making, using and disposing of a product.
What does a life-cycle assessment look at?
Cradle: Materials and energy used in manufacturing
Use: energy, water and substances used during utilisation
Grave: energy and space needed to dispose the product
Why is recycling good?
- Conserves limited raw materials
- Reduces waste
- Reduces energy usage
- Reduces release of harmful substances
What happens during processing in recycling?
- Metals are heated, and poured into moulds making ingots.
- Paper is mixed with water, cleaned and made new paper
- Glass and some polymers are heated and moulded into new objects
