chemistry paper 1

• Nanotubes


  A nanotube is like a layer of graphene, rolled into a cylinder. The length of a nanotube is very long compared to its width, so nanotubes havehigh length to diameter ratios.Nanotubes havehigh tensile strength, so they are strong in tension andresist being stretched. Like graphene, nanotubes arestrong and conduct electricity because they have delocalised electrons.These properties make nanotubesuseful for nanotechnology,electronics and specialised materials.
• diatomic elements:

  have no fear of ice cold beer


  H2, N2, F2, O2, I2, Cl2, Br2
• electrolysis: how many ions are made in a melt vs a solution and why?

  - melt: 2 ions

  - solution: 4 ions because it is mixed with water ( hydroxide + hydrogen ions )
• In the electrolysis of an aqueous solution, what product is formed at the negative electrode, and what product is formed at the positive electrode (hypothesis) ? Think best dancer.....


  - negative electrode: if the metal is above hydrogen in the reactivity series hydrogen is formed

  - positive electrode: if the ion in group seven then it is formed ( otherwise usually hydroxide
• What are elements made of

  only one type of atom
• What can elements


  notbe broken down into?Simpler substances
• Where are elements listed?

  On the periodic table
• Elements are either...


  Metal or non-metal
• What are compounds?


  Substances made from two or more elementschemically joined( i.e bonded )
• Compounds have ...


  Different properties from the elements from which they have been made
• Compounds are difficult to..


  Break back down into elements ( because chemically joined )
• What are mixtures?


  Substances containing two or more different elements that arenot chemically bonded together
• different ways mixtures can easily be separated:

  - filtration

  - evaporation

  - crystallisation

  - distillation

  - fractional distillation

  - separating funnel

  - chromatography
• Name the 5 scientists who helped make the most important advancements to the atomic structure (in order)

  - John Dalton

  - JJ Thompson

  - Ernest Rutherford

  - Niels Bohr

  - James Chadwick
• Describe the work of John Dalton (atomic structure)


  - early 1800s- used experiments to suggestsubstances were made up of tiny spheres called atoms(fundamental building blocks of nature)- suggestedchemical elements each had their own atomswhich differed by mass-discovered the electron(by applying high voltages to gases at low pressure)
• Describe the work of JJ Thomson (atomic structure)

  - late 1800s- suggested theplum pudding model of atoms
• What is the plum pudding model?

  - tiny negatively charged electrons embedded in a cloud of positive charge

  -as atoms are neutral the number of electrons and protons must be equal

  
• Describe the work of Ernest Rutherford


  - 1909- based on his suggestions on the gold foil/ alpha particle experiment conducted by Geiger and Marsden- suggested that the positive charge (protons) are found concentrated in a central part of the atom, its nucleus.This is the nuclear model of the atom
• Describe the gold foil/alpha particle experiment

  - conducted by Geiger and Marsden

  - positively charged alpha particles were shot at gold foil and expected to go straight through, but actually scattered/deflected
• Describe the work of Niels Bohr

  - 1914- suggested electrons orbit the nucleus at set distances i.e.energy levels- Bohr's theoretical calculations agreed with experimental observations
• Describe the work of James Chadwick

  -1932

  - discovered the neutron, this supported Ernest Rutherford's proposal
• What are all substances made of?

  atoms, which are the smallest indivisible particles that make up matter
• What are atoms made of? Where are these constituents found?

  - protons, neutrons, electrons

  - protons and neutrons found in the nucleus, electrons found in the energy levels (shells) surrounding the nucleus

  
• Which number is the atomic mass/nucleon number?

  The oneabovethe chemical symbol - the protons and neutrons (in the nucleus)

  
• Describe the sub-atomic particle

  proton...relative charge,relative mass, and what it helps toidentify- +1

  - 1

  - elements
• Describe the sub-atomic particle

  neutron...relative charge....relative mass....helps to define...- 0

  - 1

  - isotopes
• Describe the sub-atomic particle

  electron...relative charge.....relative mass....helps to define...- -1

  - negligible/zero

  - ions
• What is the atomic number? (periodic table)

  The number of protons/electrons in an element,belowthe chemical symbol
• Why do atoms have no charge?

  Because they contain an equal number of protons and electrons (positive and negative charges)
• What do atoms of the same element have in common? What determines what kind of element it is?

  - same number of protons in the nucleus

  - the protons determine what kind of element it is
• What is the size of an atom?

  0.1 nanometers

  1 x 10⁻¹⁰ m
• What is the size of an atom's nucleus?

  Less that 1/10,000 of the atom (like a fly in Wembley stadium)
• Where is all the mass of the atom concentrated?

  In the nucleus
• What are isotopes?


  atoms with the same number of protons (i.e. atomic number) but different number of neutrons (i.e. atomic mass)
• Describe the properties of isotopes?


  - Have similar chemical properties (similar reactions)

  - Have different physical properties (i.e. density)
• What are ions?


  charged particles that result due to there being more or less electrons to protons
• Describe how negative or positive ions form?

  - negative ions are formed when electrons aregained(because there will be more negative charges than positive charges)- positive ions are formed when electrons arelost(because there will be more positive charges than negative charges)
• How are electrons in an atom arranged?

  - in energy levels (shells)

  - the lowest energy level must be filed first

  
• What determines how an atom reacts?

  The number of electrons in its outermost shell
• The periodic table developed as chemists tried to classify the elements...:

  - without knowing much about atoms

  - with some chemical compounds mistakenly thought to be elements

  - without knowing the complete list of elements