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67 Cards in this Set
- Front
- Back
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What is mass number? |
Total number of protons and neutrons |
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What is atomic number? |
Number of protons |
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What is a compound? |
2+ elements chemically combined |
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What is an isotope? |
Different atomic forms of the same element, with the same amount of proton but a different number of neutrons |
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What is ionic bonding? |
Atoms lose or gain electron to form ions which are then attracted to eachother, 1 electron - loses, nearly full shell - gains |
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What is an ionic compound? What is its properties? |
Giant ionic lattices in regular arrangement. • High melting/boiling points - attraction • Dissolve easily • When melted/dissolved the ions can move freely |
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What is an ion? |
An atom with an electric charge. It has lost or gained electrons. |
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What is covalent bonding? |
Atoms sharing electrons in their outer shells. |
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What is a covalent bond? |
A shared pair of electrons. |
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What are the properties of a simple covalent substance? |
• Strong covalent bonds • Weak forces of attractions • Low melting/boiling points • Mostly gases/liquids • No ions - no electric charge |
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What are the properties of a macromolecule? |
• Bonded to eachother with strong covalent bonds • High melting/boiling points • Don't (normally) conduct electricity |
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What are the examples of macromolecules? |
Diamond - Each atom has 4 covalent bonds, rigid structure, very hard. Graphite - Only 3 bonds, allows for sliding of layers (weak intemolecular forces). Each atom has a delocalised electron which can conduct energy. Silicon dioxide |
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What is a metallic bond? How does a metallic bond give metals some of their properties? |
There is strong attraction between closely packed positive ions and delocalised electrons which can move through the whole structure. |
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What is an alloy? What is an important property of alloys? |
A compound of 2+ metals. Different sized atoms will disrupt the layers making them harder (can't slide over eachother) |
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What is a smart material? Give an example |
A material that behaves differently depending on conditions (temperature) Nitinol - Shape memory alloy, goes back to remembered shape when it's heated |
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What is a nanoparticle? |
1-100nm in size, contains a few hundred atoms |
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What is a fullerene? What are its properties? What can they be used for? |
Carbon molecules in hexagonal rings, shaped like hollow balls/closed tubes. Different ones will have a different number of atoms. They can be joined to form nanotubes, and the covalent bonds make them strong. Can reinforce graphite in tennis rackets. |
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What are some new developments in nanoscience? |
Big surface area:volume - Catalysts Specific sensors - Detect one molecule Strong, light building materials New cosmetics (Deodorants) Nanomedicine - Drugs to the cells Lubricant coatings - Reduce friction (Gears) Electrical circuits - Made of carbon |
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What are the properties of thermosoftening polymers? |
Individual tangled chains held by weak intermolecular forces. Free to slide over eacother and easy to melt into new shapes. |
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What are the properties of thermosetting polymers? |
Strong intermolecular forces between chains (crosslinks), strong, hard and rigid. |
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How do you create high/low density polymers? |
High - low temperature and pressure (w/ catalyst) Low - High temperature and pressure |
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What is relative atomic mass? |
How heavy different atoms are compared with the mass of Carbon-12. It's an average value for all isotopes of the element. |
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What is relative formula mass? |
Sum of all the relative atomic masses of the atoms in the formula. |
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What is a mole? |
Relative formula mass of a substance in grams. |
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How you work out the % mass of an element in a compound? |
(Mr (of the element)/Mr (of the compound))*100 |
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How do you work out the empirical formula? |
Mass/Ar of element |
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How do you calculate masses in a reaction? |
• Write out the balanced equation • Work out the Mr • Divide to a get a ration of 1:x then multiply by the original mass |
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How do you calculate percentage yield? |
(Actual yield/Predicted yield)*100 |
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What reasons could there be for yeilds being less than 100%? |
• Reversible reactions will continually react • Some product is lost when it's separated from the mixture (Filtering a liquid to remove solid) • Sometimes there can be unexpected reactions |
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What is a reversible reaction? |
Products of the reaction can react to produce the original reaction. |
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What is the method for paper chromatography? |
• Food colouring in a cup - few drops of solvent • Put spots of that solution on a pencil baseline on filter paper. • Roll the sheet and place into a beaker of solvent (baseline above solvent) • The solvent moves the dyes up, forming spots |
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What are the advantages of using machines instead of paper chromatography methods? |
Very sensitive Fast - Can be automated Accurate - useful for small sample |
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What is the method for gas chromatography? What happens when you link it up to a mass spectrometer? |
The sample is dissolved in a solvent, then carried through a column with a solid material by a gas. The different substances are separated out as they travel at different speeds. The recorder draws a gas chromatograph and the position of the peaks shows the retention times of the substances. A mass spectrometer enables you to identify the substances - the molecular ion peak shows the Mr. |
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What effects rate of reaction? How do you work out rate of reaction? |
Temperature, concentration, catalysts, surface area. Amount of reactant used or product formed/time |
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What are different methods for measuring the rate of reaction? |
Precipitation - How long it takes for a mark to disappear (Solution must be see through) Results are subjective. Mass change - (Produces gas) Measure the mass that disappears, most accurate but releases gas. Volume of gas - Measure gas with syringe |
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How do you measure the reaction between HCL and marble chips? |
Measure volume of gas at regular intervals, repeat but increase the surface area - faster rate |
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How do you measure the reaction between Magnesium metal and dilute HCL? |
Gives off hydrogen, increase the concentration of the acid - faster rate |
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How do you measure the reaction between Sodium thiosulfate and HCL? |
Clear solution and produces a precipitate of sulfur, watch a mark disappear, increase the temperature/concentration |
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What is the formula for the decomposition of Hydrogen peroxide? How would you increase the rate of reaction? |
2H202 -> 2H20 + 02 Add a manganese oxide catalyst to speed it up, oxygen gas is given off so use a gas syringe |
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What is collision theory? |
More collisions = Faster rate of reaction High temperature -> Particles move faster Higher concentration -> More particles in a smaller space Larger surface area -> More places to collide |
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What is activation energy? |
The minimum amount of energy needed by particles to react. |
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What is a catalyst? What does a solid catalyst do? |
A substance which speeds up a reaction without being changed/used up. A solid catalyst gives the reacting particles a surface to stick to. |
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What are the advantages and disadvantages of using catalysts in industry? |
Increase the rate of reaction - save money Work at lower temperatures ~~~~~~~~~~~~~ But are expensive and need to be cleaned Different products need different catalysts Impurities will stop them working |
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What is an exothermic reaction? Examples? |
Transfers energy to the surroundings, usually as heat - shown by a temperature rise Combustion, neutralisation reactions, oxidation reactions, hand warmers, self heating cans |
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What is an endothermic reaction? Examples? |
Takes energy from the surroundings as heat - fall in temperature Thermal decomposition, sports injury packs |
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What is the relation between reversible reactions and endo/exothermic reactions? Example? |
They can be endothermic and exothermic. Hydrated copper sulfate <-> anhydrous copper sulfate + water. Heat the blue crystals to leave a white powder. Add water to the powder for blue crystals |
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What are important values on the pH scale? Universal indicator? |
Strongest acid - 0, strongest alkali - 14, neutral - 0 A combination of dyes that change colour based on pH. |
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What is an acid, alkali, and base? |
Acid - pH<7 from H+ ions in water Base - ph>7 Alkali - Base that dissolves in water from OH- ions in water |
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What is the formula for a neutralisation reaction? |
acid + base -> salt + water H+ + OH- -> H20 |
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What are the formulas for the Acid + metal reactions? |
Acid + Metal -> Salt + Hydrogen Acid + Metal Carbonate -> Salt + C02 + H20 Acid + Metal Oxide -> Salt + H20 Acid + Metal Hydroxide -> Salt + H20 |
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What salts do the different acids make? |
Hydrochloric acid (HCL) - Chloride salts Sulfuric acid (H2SO4) - Sulfate salts Nitric acid (HNO3) - Nitrate salts /can make nitrogen oxide with metals/ |
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In salt reactions how do metals affect the reaction? |
More reactive the metal the faster the reaction, copper doesn't react. The speed of reaction is indicated by the rate of bubbles, confirmed by the splint test. |
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How is ammonia nitrate made? What is it used for? |
Ammonia dissolves in water to make an alkalie, then reacting with nitric acid it produces a neutral salt. NH3 + HN03 -> NH4NO3 It is a good fertiliser as it has a lot of nitrogen |
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Which products are soluble? Insoluble? |
Soluble: Most chlorides, most sulfates, most nitrates Insoluble: Oxides, hydroxides, lead chloride, lead sulfate, silver chloride |
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How do you make a soluble salt with a metal/insoluble salt? |
Pick the right acid, plus a metal/insoluble base (For salt AB, get B acid and A metal) Add A to the acid, it dissolves, excess solid will stick to the bottom. Filter out the excess for the salt solution. To get pure crystals evaporate the water, then leave the rest to evaporate slowly. |
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How do you make a soluble salt with an alkali? |
Use this as you won't be able to tell whether the reaction has finished. Add the right amount of alkali to neutralise the acid - use an indicator. Repeat with the same volumes (salt won't be contaminated with indicator) Crystallise the salt |
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How do you make insoluble salts? |
Precipitation reaction Pick 2 soluble solutions with the ions you need (Lead chloride = Lead nitrate + sodium chloride) Once the salt has precipitated, filter it from the solution, wash it and dry on filter paper. Useful for removing poisonous ions from drinking water, and making water soft. |
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What is electrolysis? What is required for electrolysis? |
Decomposition by passing an electric current through a solution containing ions. Electrons taken at anode, given at cathode. As they lose/gain electrons they become atoms/molecules Needs an electrolyte, which contains free ions to conduct electricity. |
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What is oxidation? Reduction? |
Oxidation - Loss of electrons Reduction - Gain of electrons |
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What occurs at electrolysis in molten salt? |
Cathode - -ve ions lose electrons Anode - +ve ions gain electrons |
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What occurs at electrolysis in a solution? |
Cathode - OH- and Halide ions present, Halide OH- present, oxygen present Anode - Metal ion more reactive than H, H produced Less reactive than H, metal produced (More reactive elements want to stay as ions Solution - Whatever is left forms in the solution
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How do you create a half equation? |
Make the number of electrons the same for both half equations. Anode : 2H+ + 2e- -> H2 Cathode : 2Cl- -> Cl2 + 2e- |
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What are useful products from electrolysis of sodium chloride solution? |
Chlorine - Bleach and plastics Sodium Hydroxide - Strong alkali, soap |
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How do you electrolyse Aluminium? |
Mine and purify bauxite to produce a white powder (aluminium oxide), then electrolyse it to make Aluminium. Electrodes are graphite (conductor) -ve electrode: Al3+ + 3e- -> Al +ve electrode: 202- -> O2 + 4e- Oxygen reacts with the electrodes to make CO2 so the positive electrodes have to be replaced. |
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What is cryolite used for? |
Dissolving Al2O3 in molten cryolite will bring its melting point down from over 2000C to 900C which makes it cheaper. |
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What is electroplating? How do you electroplate something? |
Electrolysis to coat the metals surface with another metal. -ve electrode - metal object +ve electrode - Pure metal (top up electrolyte) Electrolyte - Ions of the plating metal |
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What is electroplating used for? |
Decoration - Plate a brass cup with silver, cheaper than a silver cup Conduction - Copper plates metals for electronic circuits and computers |
