Chemistry Paper 1

• What is an atom?


  An atom is the smallest part of an element that can exist.
• What is an element?


  An element is a substance of only one type of atom.
• How are the elements listed and approximately how many are there?


  They are listed in the periodic table; there are approximately 100.
• What are the two groups into which elements can be classified based on their properties?

  Metals and non-metals.
• What are the new substances called that are formed when elements combine through chemical reactions?


  Compounds.
• What is a compound?


  A compound is two or more elements combined chemically in fixed proportions which can be represented by formulae.
• Do compounds have the same properties as their constituent elements?


  No, they have different properties.
• What is a mixture and does it have the same chemical properties as its constituent materials?


  A mixture consists of two or more elements or compounds not chemically combined together; it does have the same chemical properties.
• What are the methods through which mixtures can be separated?

  Filtration, crystallisation, simple distillation, fractional distillation, and chromatography.
• Do the methods of separating mixtures involve chemical reactions?


  No, they do not involve chemical reactions.
• Describe and explain simple distillation.

  Simple distillation is used to separate liquid from a solution – the liquid boils off and condenses in the condenser, with the thermometer reading the boiling point of the pure liquid.
• What is the difference between evaporation and crystallisation?


  Evaporation removes all the solvent, while crystallisation removes some solvent to form a saturated solution.
• Describe and explain fractional distillation.

  Fractional distillation separates a mixture of liquids with different boiling points using a fractionating column to condense and vaporize the liquids at different heights.
• Describe and explain filtration.

  Filtration separates an insoluble solid suspended in a liquid, where the solid (residue) is caught in filter paper and the liquid that passes through is called the filtrate.
• Describe and explain chromatography.


  Chromatography separates a mixture of substances dissolved in a solvent by placing a spot of the mixture on paper and allowing the solvent to rise and separate the components.
• What is a separating funnel?


  A separatory funnel is an apparatus for separating immiscible liquids.
• Describe the plum-pudding model of the atom.


  The atom is a ball of positive charge with negative electrons embedded in it.
• Describe the Bohr/nuclear model and how it came about.


  The nuclear model suggests that electrons orbit the nucleus at specific distances (shells) and came about from the alpha scattering experiments.
• What are the smaller positive particles discovered in the nucleus called?


  Protons.
• What did the work of James Chadwick provide evidence for?


  The existence of neutrons in the nucleus.
• Describe the structure of an atom.


  The atom has a small central nucleus (made up of protons and neutrons) around which there are electrons.
• What are the relative masses and charges of the proton, neutron, and electron?


  Masses: 1, 1, very small; Charges: 1, 0, -1 (respectively).
• Why are atoms electrically neutral?


  They have the same number of electrons and protons.
• What is the radius of an atom?


  0.1 nm.
• What is the radius of a nucleus compared to that of the atom?


  The radius of a nucleus is $1 \times 10^{-14} \text{ m}$ and is approximately 1/10000 of the radius of the atom.
• What name is given to the number of protons in the nucleus?


  The atomic number.
• What is the radius of an atom?


  0.1 nm
• What is the radius of a nucleus compared to that of an atom?


  The radius of a nucleus is $1 \times 10^{-14} \text{ m}$ and is 1/10000 of the atom's radius.
• What is the name given to the number of protons in the nucleus?

  Atomic number
• Atoms of the same element have the same number of which particle in the nucleus?


  Protons
• Where is the majority of the mass of an atom located?

  The nucleus
• What is the mass number?


  The total number of protons and neutrons.
• How does one calculate the number of neutrons using mass number and atomic number?


  Subtract the atomic number from the mass number.
• What is an isotope?


  Atoms of the same element that have a different number of neutrons.
• Do isotopes of a certain element have the same chemical properties?


  Yes, they have the same electronic structure.
• What is the relative atomic mass?


  The average mass value which takes the mass and abundance of isotopes into account.
• What are the electronic configurations of He, Be, F, Na, and Ca?


  • He: 2
  • Be: 2,2
  • F: 2,7
  • Na: 2,8,1
  • Ca: 2,8,8,2
• What are ions?


  Ions are charged particles formed when atoms lose or gain electrons.
• What is formed when a metal reacts with a non-metal?


  An ionic compound made of positive and negative ions.
• What is formed when a non-metal reacts with a non-metal?


  A molecular compound containing covalently bonded atoms.