yr 9 science

• particle: the tiny pieces that all matter is made from.
• atom: the smallest independent particle. everything is made of atoms.
• size of atoms: about 1 x 10 to the power of -10 m in diameter. it's 0.1 nanometre.
• there are 3 subatomic particles in an atom. protons, neutrons, and electrons.
• protons have a mass of 1, charge of +1 and is located in the nucleus.
• neutrons have a mass of 1, charge of 0 and is located in the nucleus.
• electrons have a mass of 0 or 1/1835, it has a charge of -1 and is located on the shells orbiting the nucleus
• rutherford's experiment. he fired alpha particles at gold leaf, used a phosphor-coated screen to track where they all went.
• atomic number: the number of protons in the nucleus of an atom.
• atomic mass: gives you the total protons and neutrons together.
• isotopes are different forms of elements with the same atomic number but different atomic masses due to having different numbers of neutrons.
• the noble gases are also known as group zero because they don't react easily with other substances.
• the periodic table is organised by increasing atomic number (proton count).
• groups are columns on the periodic table that contain elements with similar properties.
• periods are rows on the periodic table that contain elements with similar electron configurations.
• relative atomic mass: the average weight of the masses of all the isotopes of an element.
• ar= ((decimal% x atomic mass) + (decimal% x atomic mass)/100)
• dmitri mendeleev, a russian chemist, arranged the elements in order of increasing atomic weight.
• mendeleev left gaps where no known element fitted and predicted these would be filled with newly discovered elements.
• electron configuration: the number of electrons in each shell.
• 1st shell=2, 2nd shell=8, 3rd shell=8
• what is a chemical reaction?

  a change in which two or more new substances are formed.
• what is a physical change?

  a change in which no new substances are formed.
• what does exothermic mean?

  when energy leaves the substance. 'exits'
• what does endothermic mean?

  when energy enters the substance. like absorb.
• is metal a natural or man-made material?

  natural
• is nylon a natural or man-made material?

  man-made
• state why iron and steel are used for building bridges

  they're strong and durable.
• solids have a fixed volume and fixed shape.
• liquids have a fixed volume but can flow.
• gases do not have a fixed shape or volume.
• describe what happens to the waste at a landfill

  it's spread out in the land
• describe one problem landfill sites cause


  it uses up s lot of space which could be used for building new infrastructure.
• is condensation a physical change or a chemical change?

  a physical change
• is evaporation a physical change or a chemical change?

  a physical change
• is neutralisation a physical change or a chemical change?

  a chemical change.
• describe 2 differences between physical change and chemical reaction

  • no new substances are formed in a physical change however two or more new substances are formed in a chemical reaction
  • physical changes are reversable however chemical reactions aren't
• what is a pathogen?

  a microbe that causes disease in another living organism.
• what is latent heat?


  the energy needed to break the bonds between particles in melting or evaporating, or the energy released when these bonds form in condensing or freezing.
• what is specific heat capacity?

  the energy needed to raise the temperature of 1kg of a substance by 1c.