Chemistry IGCSE

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Chemistry IGCSE
2014-04-14 04:56:11

Study flash cards for Chemistry
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  1. What is an atom?
    An atom is a collection of particles that makes a small-scale structure.
  2. What is a molecule?
    A molecule is a group of atoms joined by the forces of attraction.
  3. What is diffusion?
    Diffusion is the mixing of two substances.
  4. What are the three groups of matter?
    • They are: 
    • Elements - composed of only one type of atom
    • Compounds - molecule with more than one type of atom
    • Mixtures - collections of diff. molecules or atoms that are not bonded
  5. Name and shortly explain 5 separation techniques.
    • Filtration - separation of a liquid and a solid
    • Simple distillation - separation of two liquids
    • Fractional distillation - separation of three or more liquids
    • Paper chromatography - separation of substances with diff. colours
    • Crystallisation - separating a liquid from a solid (dilute)
  6. What are all the components of the distillation apparatus?
    • 1 heat source
    • 2 Still pot
    • 3 still head
    • 4 thermometer 
    • 5 condenser
    • 6 cooling water in
    • 7 cooling water out
    • 8 distillate flask
    • 9 vacuum/ gas inlet
    • 10 still receiver
    • 11 heat control
    • 12 stirrer speed control
    • 13 stirrer heat plate
    • 14 heating (oil/sand) bath
    • 15 mixture in flask
    • 16 cooling bath
  7. What is an ion?
    Through the interaction with other atoms, an ion is a non-neutrally charged atom.
  8. Describe reduction and oxidation.
    • Reduction is the gain of electrons
    • Oxidation is the loss of electrons
  9. What is an ionic bond?
    • usually a bond between a metal and a non-metal/polyatomic ion. 
    • The metal donates one electron to the non-metal.
  10. How strong the force of attraction between two ions? Why?
    Quite strong because they are oppositely charged.
  11. Name 3 properties of ions.
    Nearly all have very high melting and boiling points

    Most are soluble in water

    Do not conduct electricity in the solid state but do in molten and aqueous states.
  12. What is a covalent bond?
    • A covalent bond is the sharing of electron pairs between atoms. 
    • It normally occurs between non-metals.
  13. How strong are the forces of attraction between covalent bonds?
    Typically they are weak due to the fact that they only have a few atoms in their molecular structure.
  14. Name 4 characteristics of covalent bonds.
    • Tend to be gasses, liquids or soft solids. 
    • Poor conductors of heat and electricity.
    • Non-electrolytes.
    • Molecules.
  15. Why can electron of a metal move freely inside a structure?
    Because they aren't tightly bonded and can become delocalised by jumping from one atom to the next.
  16. How does a metal conduct electricity?
    Due to its structure, electrons are attracted to the negative potential and can conduct electricity.
  17. Why are metal malleable?
    Metals are malleable (beaten into sheets) and ductile (pulled out into wires) because they can change form without breaking their metallic bonds.
  18. What is electric current?
    It is the flow of electrons or ions.
  19. Why do covalent compounds not conduct electricity?
    Because in this case not only the nuclei of the atoms are bonded but also the electrons, stopping them from moving freely, thus conducting electricity.
  20. Why do ions only conduct electricity in the molten or aqueous states?
    In the solid state they are unable to move, whereas if they are in the liquid or aqueous states, they are free to move within that liquid.
  21. Describe 3 simple experiments which test whether a substance is electrolyte or not.
    • 1. Conductivity probe:
    • The probe is lowered into the liquid and if a current is detected ...
    • 2. Electrolysis: 
    • 3. Electrolysis of molten salts:
  22. What is a group and period?
    In the periodic table of elements, there a seven vertical columns of elements aka 7 groups. The periods are horizontal.
  23. Why do elements of the same group have similar chemical properties?
    Because they have the same number of covalent electrons.
  24. Why are noble gasses unreactive?
    Noble gasses are unreactive because they have a full covalent shell and so do not react with other atoms.
  25. How can you recall the positions of metals and non-metals in the periodic table of elements?
    • B - Bi 
    • At is non-metal + H.
  26. What are the classification of metals?
    • Alkali Metals
    • Alkaline Earth Metals
    • Transition Metals 
    • Post Transition Metals 
    • Non-metals with some metallic properties
    • Other Non-Metals
    • Halogens
    • Noble Gasses
  27. How can you classify an element as metal or non-metal?
    • By considering its conductivity and Acid/Base oxides. 
    • Metals produce oxides that are bases in nature (high pH)
    • Non-metals produce acidic (low pH)
  28. What are the reactions between Lithium, Sodium and Potassium with water?
    • Lithium - the metal floats and fizzes
    • Sodium - the metal floats and becomes sphere of molten metal
    • Potassium - bursts into flames
  29. What are the colours and states of the following elements at room temperature?
    Fluorine, Chlorine, Bromine and Iodine
    • Fluorine yellow gas
    • Chlorine green gas
    • Bromine brown liquid
    • Iodine purple solid
  30. In which direction (up or down) is the reactivity of elements increasing for group 7 elements?
    Going upwards
  31. In which direction (up or down) does reactivity increase for group 1 elements?
    Going down.
  32. How can you ionise hydrogen chloride gas?
    By dissolving it in water. It also becomes HCL acid and is no longer a covalent compound.
  33. Recall the gasses present in air and their approximate percentage by volume.
    • Nitrogen - 78.08 %
    • Oxygen - 20.9 %
    • Argon - 0.9 %
    • Carbon dioxide - 0.04 %
    • Neon - 0.002 %
    • ...
    • ...
  34. What are 3 ways of determining the oxygen content in air?
    • Burning phosphorus: P4 + 5O2 ==> P4O10
    • Place a bell jar with a plate of phosphorus in a tank of water. 
    • Light the phosphorus and the bell jar is sealed. 
    • The water level rises by the amount of oxygen that is burned up.

    Iron - Using damp iron wool in a tube in a tank and wait a week. The water level also rises because the iron rusting.

    • Copper - Using two glass syringes and a silica filled with copper.
    • The copper is heated and so combines with oxygen forcing the glass syringes to move.
  35. How can you make oxygen form hydrogen peroxide?
    • Hydrogen peroxide solution is dripped onto manganese (IV) oxide (catalyst).
    • The H2O2 breaks up and oxygen builds up and passes through a tube into an inverted jar submerged in water.
  36. What are the reactions of oxygen with burning magnesium, carbon and sulphur?
    • 2Mg(s) + O2(g) ==> 2MgO(s) 
    • White coloured compound 

    • C(s) + O2(g) ==> CO2(g)
    • Carbon dioxide

    • S(s) + O2(g) ==> SO2(g) 
    • Sulphur dioxide
  37. What happens when metals (and non-metal) oxides are mixed with water?
    • Some metal oxides create small amounts of hydrogen ions (alkaline in nature)
    • Non-metal oxides some create an acidic solution.
  38. Describe the laboratory preparation of carbon dioxide from calcium carbonate and hydrochloric acid.
    • Dilute HCL is dripped onto marble chips and the gas produced is collected in a glass jar.
  39. Describe the formation of CO2 form the thermal decomposition of metal carbonates.
    • When most metal carbonates are heated strongly they decompose and give off CO2. 
  40. What are the 2 important properties of CO2?
    • It dissolves in water easily 
    • It is heavier than air
  41. How can you produce acidic solutions?
    • By using CO2, we can change the pH of water. 
    • CO2 + H2O ==> H2CO3
    • H2CO3 + H2O ==> HCO3(-) + H30(+)
  42. How can you make water from hydrogen?
    Hydrogen is a very flammable gas, which when burns combine with the oxygen in the air and forms water.
  43. What is the test for the presence of hydrogen?
    Even a small amount will burn with a loud pop in a test tube.
  44. What are the 2 tests for water?
    Using anhydrous copper sulphate powder, it'll turn blue from white. 

    using cobalt chloride paper, it'll turn white from blue.
  45. What is the physical test to see if a sample of water is pure?
    The sample's boiling and freezing points are tested and if they are at exactly 100 degrees C and 0 degrees C the sample is pure water.
  46. List the reactivity series of metals in order.
    • Potassium
    • Sodium
    • Lithium 
    • Calcium
    • Magnesium
    • Aluminium
    • Zinc
    • Iron 
    • Tin
    • Lead
    • Copper
    • Mercury
    • Silver
    • Gold
  47. How can reacting with water and dilute acid be use to deduce the order of reactivity: potassium, sodium, lithium, calcium, magnesium, zinc, iron and copper?
    Each reaction between these is somehow unique; the amount of bubbles that flow at a time is different. So you can tell which reacts stronger, placing it higher in the reactivity series.
  48. Explain the reactions of magnesium, aluminium, zinc and iron with dilute acid.
    • Magnesium - rapid flow of bubbles
    • Aluminium - slower flow
    • Zinc - slow
    • Iron - very slow
  49. How can you use a displacement reaction to determine where a metal is in the reactivity series?
    You add a metal in powered form to a metal in a solution and if the powered metal is more reactive (i.e. higher in the reactivity series) it will replace the first metal.
  50. What is the chemical reaction of rusting and the oxidation and reduction reaction of rusting?
    Fe + H2O + O2 ==> Fe2O3

    • Oxidation : Fe(s) ==> Fe2(+)(AQ) + 2e-
    • Reduction: O2 + 4e- + 4H(+) ==> 2H2O
  51. What do you call the substance that is being oxidised (and reduced)?
    Reductant (oxidant)
  52. What two conditions must be met for iron to rust?
    Oxygen and water.
  53. What are the two main types of rust prevention?
    Barrier protection : this is when the metal is completely covered in a layer of a substance which stop the metal from coming into contact with water and oxygen. 

    Sacrificial protection: This is when the metal is coupled to a more reactive metal, which will rust instead of the first metal.
  54. What are anions and cations?
    • Anions are ions with a negative charge. 
    • Cations are ions with a positive charge.
  55. What colour are the flames of the following metals: Calcium, Lithium, Potassium, Sodium?
    • Calcium - Red
    • Lithium - Pink
    • Potassium - Lilac
    • Sodium - Orange
  56. What is the test for the ammonium ion?
    • NH4(+) is tested for by adding sodium hydroxide and heating gently. It gives off a very distinct smell. 
    • It also reacts with damp litmus paper, turning it blue (showing it is an alkali metal).
  57. What atoms can we identify by using sodium hydroxide solution?
    • Ammonium ion - smell
    • CU(2+) - pale blue that dissolves
    • Fe(2+) - pale green precipitate
    • Fe(3+) - red/brown precipitate
  58. What atoms can we identify by using silver nitrate and dilute nitric acid?
    • If halogens are precent, a precipitate will form. 
    • Br(-) - pale yellow precipitate that dissolves in ammonia solution

    Cl(-) - thick white precipitate dissolves in ammonia solution

    I(-) - pale yellow precipitate that does not dissolve in ammonia solution.
  59. How can you test for the sulphate ion?
    • SO4(2-) can be tested for by adding the substance to a solution of barium chloride.
    • A white precipitate forms which does not dissolve in dilute hydrochloric acid.
  60. What is the test for carbonate?
    CO3(2-) can be tested by adding the substance to dilute hydrochloric acid, carbon dioxide gas should be given off.
  61. What is the test for CO2 gas?
    Bubble the gas through lime water (calcium hydroxide solution). It turns cloudy.
  62. What is the test for hydrogen gas?
    Put a lit splint into a sample of the gas and if it burn with a loud "pop" sound, it is hydrogen.
  63. What is the test for oxygen gas?
    If you put a glowing splint into a sample of the gas and it re-lights, it is oxygen.
  64. What is the test for ammonia gas?
    Expose to damp litmus paper and it'll turn blue.
  65. What is the test for chlorine?
    Expose to damp litmus paper and it is bleached white.
  66. What is the general formula for alkanes?
  67. Name the first five alkanes.
  68. What happens when alkanes are burned?
    • there are two possible outcomes:
    • Complete and incomplete combustion. 
    • When it combusts completely the alkane reacts with oxygen in the air. 
    • when an incomplete combustion take place the following products are created: 

    • carbon (soot) (indicator)
    • water
    • CO
  69. What happens when methane and bromine are exposed to UV light?
    • A substitution reaction takes place resulting in hydrogen bromide and bromomethane.
    • The brown (bromide) disappears. 
  70. What is the general formula for alkenes?
  71. What happens when an alkene reacts with bromine?
    • (Bromine solution or water)
    • An addition reaction takes place. The double bond is broken and two bromine atoms are added to the molecule. 
    • Detect carbon double bond.
  72. Explain the pH scale
    • 0 - 14 
    • (Strongly acidic - Neutral - Strongly Alkaline)
    • Concentration of H+ ions.
  73. How can you use litmus paper to measure pH?
    • The colour the litmus paper changes to depends on the acidity of the solution. 
  74. How can you use phenolphthalein to measure pH?
    • phenolphthalein is colourless below pH 8.0 and become deep red as of pH 10.0
  75. How can you use methyl orange to measure the pH of a solution?
  76. How does the universal indicator work?
    • It changes colour AND shows how acidic or basic a solution is. 
  77. What are acids and alkalis made of?
    • Acids are made of hydrogen H+ ions
    • Alkalis are made of hydroxide OH- ions
  78. State all the solubility rules
  79. How can you make soluble salts?
    This method does not work for sodium, potassium and ammonium.

  80. How can you make insoluble salts?
  81. How can you make salts with sodium, potassium and ammonia?
    With titration. You add and alkali (base) to an acid. The acid already has an indicator added to it.

  82. What are exothermic and endothermic reactions?
    • Heat is taken in.         Heat is given out.
  83. Describe the combustion calorimetry experiment.
    • We measure the mass of the burning sample and the water. During the combustion, we measure the rise in temperature.
  84. What is the diff. between endothermic and exothermic reactions?
    • In exothermic reactions bonds are made or strengthened (EMITS)
    • In endothermic reactions bonds are broken (ABSORBS)
  85. What are catalysts?
    Catalysts are substances which when added to a reaction, allow the reactants to come together more easily.
  86. What characteristics effect the rates of reaction?
    Surface area, temperature, concentration and pressure.
  87. What is the activation energy in a reaction?
    It is the minimum energy required to start a chemical reaction.