chemistry paper 1

• What is a compound?

  A compound is a substance that contains two or more different types of atoms chemically bonded together
• What is the chemical formula for water?

  H2O
• How do we represent a chemical reaction?

  We can represent a reaction with a word equation and a chemical equation using symbols
• Why must chemical equations be balanced?

  Atoms are not created or destroyed in any chemical reaction, so the same number of each type of atom must be on both sides
• What is the first step in balancing a chemical equation?

  Start balancing atoms that are only in compounds
• What is a mixture?

  A mixture is any combination of different types of elements and compounds that aren't chemically bonded together
• Give an example of a mixture.

  Air, which is a mixture of oxygen, nitrogen, and more
• How can large insoluble particles be separated from a liquid?

  Using filtration
• What is crystallization?

  Crystallization leaves a solute behind after evaporating the solvent from a solution
• What is distillation?

  Distillation involves heating a solution and cooling the gas to condense it back into a liquid
• What is fractional distillation?

  Fractional distillation separates different liquids in a mixture based on their boiling points
• What are the three main states of matter?

  Solid, liquid, and gas
• How do particles behave in a solid?

  Particles vibrate around fixed positions
• How do particles behave in a gas?

  Particles are far apart and move randomly with high energy
• What is required to melt or evaporate a substance?

  Energy, usually in the form of heat, to overcome electrostatic forces of attraction
• What do state symbols indicate in chemical equations?

  State symbols indicate the physical state of substances: (s) for solid, (l) for liquid, (g) for gas, and (aq) for aqueous
• Who proposed the plum pudding model of the atom?

  JJ Thompson
• What did Ernest Rutherford discover about the atom?

  The positive charge is concentrated in a small nucleus, with electrons orbiting far away
• What did Niels Bohr discover about electrons?

  Electrons exist in shells or orbitals around the nucleus
• What are protons and neutrons collectively called?

  Nucleons
• What is the charge of a proton and an electron?

  Protons have a charge of +1 and electrons have a charge of -1
• What does the atomic number represent?

  The atomic number represents the number of protons in the nucleus
• What happens when an atom gains or loses electrons?

  It becomes an ion
• What is the mass number?

  The mass number is the total number of protons and neutrons in the nucleus
• What are isotopes?

  Isotopes are atoms of the same element with different numbers of neutrons
• What is relative atomic mass (RAM)?

  Relative atomic mass is the weighted average mass of an element's isotopes
• How is the average relative atomic mass calculated?

  By adding the total masses of all isotopes and dividing by the total number of atoms
• How did Dmitri Mendeleev contribute to the periodic table?

  Mendeleev grouped elements based on their properties, even if the order didn't follow atomic weight
• What is the maximum number of electrons in the first four shells?

  2 in the first shell, 8 in the second and third shells, and 2 in the fourth shell
• What are metals and nonmetals in the periodic table?

  Metals are to the left of the staircase and nonmetals are to the right
• What do group numbers in the periodic table indicate?

  Group numbers indicate how many electrons an atom has in its outer shell
• What are alkali metals?

  Alkali metals are in group one and have one electron in their outer shell
• How does reactivity change in alkali metals as you go down the group?

  Reactivity increases as you go down the group
• What are halogens?

  Halogens are in group seven and have seven electrons in their outer shell
• How does reactivity change in halogens as you go down the group?

  Reactivity decreases as you go down the group
• What are noble gases?

  Noble gases are in group zero and have a full outer shell
• What happens to metals when they lose electrons?

  They become positively charged ions
• What charge do group one metal ions have?

  Group one metal ions have a charge of +1
• What charge do group two metal ions have?

  Group two metal ions have a charge of +2
• What charge do group seven nonmetal ions have?

  Group seven nonmetal ions have a charge of -1