CHEMISTRY 🧪🥼

• What methods can be used to separate rock salt?

  Filtration and crystallisation
• What is rock salt composed of?

  Rock salt is a mixture of salt and sand
• Why can salt dissolve while sand cannot?

  Salt can dissolve in water, but sand cannot
• What are the steps to separate salt from sand using filtration and crystallisation?

  1. Grind the mixture to make salt crystals small.
  2. Stir the mixture in water to dissolve the salt.
  3. Filter the mixture to separate sand (residue) from salt (filtrate).
  4. Evaporate the water to obtain dry salt crystals.
• What is the approximate radius of an atom?

  About 0.1 nanometers
• What is located in the nucleus of an atom?

  The nucleus contains protons and neutrons
• Why does the nucleus have a positive charge?

  Because it contains protons, which are positively charged
• What is the relative mass of protons, neutrons, and electrons?

  Protons and neutrons have a relative mass of 1, while electrons have a very small mass
• How do electrons behave in an atom?

  Electrons move around the nucleus in electronic shells
• What determines the size of an atom?

  The volume of the electron orbits determines the size of the atom
• Why are atoms neutral?

  Atoms are neutral because they have the same number of protons and electrons
• What are ions?

  Ions are charged particles that have a different number of protons and electrons
• What does the atomic number represent?

  The atomic number tells us how many protons there are in an atom
• What does the mass number indicate?

  The mass number indicates the total number of protons and neutrons in an atom
• What defines an element?

  An element is a substance made up of atoms that have the same number of protons
• What are isotopes?

  Isotopes have the same number of protons but different numbers of neutrons
• What is the formula for relative atomic mass?

  Relative atomic mass (Ar) = (sum of abundance of all isotopes x isotope mass) / total abundance
• How do atoms combine to form compounds?

  Atoms join together to make compounds through chemical bonding
• What are the characteristics of compounds?

  • Formed from two or more elements
  • Atoms are chemically bonded
  • Fixed proportions throughout the compound
  • Chemical reactions are needed to separate original elements
• What is ionic bonding?

  Ionic bonding occurs when opposite charges of ions attract each other
• Give examples of ionic compounds.

  Magnesium oxide, sodium chloride, calcium oxide
• How do metal and non-metal atoms form ions?

  Metal atoms lose electrons to form positive ions, while non-metal atoms gain electrons to form negative ions
• What are covalent bonds?

  Covalent bonds are formed when a pair of electrons is shared between two atoms
• What are the components of a chemical equation?

  • Reactants: molecules on the left side that react with each other
  • Products: molecules on the right side that are produced
  • Must have the same number of atoms on both sides
• What is the significance of balancing a chemical equation?

  It ensures that the same amount of atoms is present on both sides of the equation
• What are mixtures?

  Mixtures are easily separated and do not have chemical bonds between their components
• What are the methods to separate mixtures?


  • Filtration
  • Crystallisation
  • Chromatography
  • Simple distillation
  • Fractional distillation
• How does paper chromatography work?

  It separates dyes in ink by using a solvent to carry the ink up the paper
• What happens if a dye is insoluble in the solvent used in chromatography?

  The dye will remain on the baseline
• What is a chromatogram?

  A chromatogram is the pattern of spots formed after chromatography
• Who proposed the "Plum pudding model" of the atom?

  JJ Thompson
• What did Rutherford's alpha particle scattering experiment demonstrate?

  It showed that the nucleus is small and positively charged
• What did Niels Bohr propose about electron arrangement?

  He proposed that electrons orbit the nucleus in fixed shells
• Who discovered neutrons?

  James Chadwick
• What is the significance of the nuclear model of the atom?

  It describes the atom as having a small nucleus surrounded by electrons in a cloud
• How did the understanding of the atom evolve from Dalton to Chadwick?

  It evolved from solid spheres to complex structures with protons, neutrons, and electrons