Chemistry 1

• Substances are made of atoms.
• A compound is a substance that contains two or more different types of atoms chemically bonded together.
• Chemical reactions involve changes in how atoms are bonded.
• Chemical equations must be balanced to have the same number of each type of atom on both sides.
• A mixture is a combination of different types of elements and compounds that are not chemically bonded together.
• Filtration, crystallization, and distillation are physical processes used to separate mixtures.
• Solid, liquid, and gas are the three main states of matter.
• Melting and evaporating are physical changes that do not create new substances.
• Atoms are made up of positive and negative charges.
• In electrolysis, cations are reduced at the cathode and anions are oxidized at the anode
• The pH scale is a logarithmic scale, not linear
• Aluminium oxide is often mixed with cryolite to reduce its melting point for easier extraction of aluminium
• Metals gain electrons to turn back into atoms and become neutral
• A strong acid dissociates completely, while a weak acid only partially dissociates
• Electrolysis can be used to purify metals or extract them from compounds
• When a substance dissolves, its ions partially dissociate
• Metals more reactive than hydrogen can displace it from an acid
• Titrations are used to determine the concentration of an acid or alkali
• The nucleus is the small, positively charged center of an atom.
• The reactivity series helps predict what will happen in a reaction between metals.
• Metals less reactive than carbon can be displaced by carbon in a smelting process.
• Oxidation is the loss of electrons, reduction is the gain of electrons.
• Percentage yield tells you how much product is actually made compared to how much could have been made.
• The concentration of solutions can be given in g/dm³ or moles/dm³.
• A more reactive metal will displace a less reactive metal from a compound.
• Atom economy tells you how much desired product you get out of a reaction compared to the mass of the reactants.
• One mole of any gas takes up a volume of 24 dm³ at RTP (room temperature and pressure).
• Electrons orbit the nucleus at a distance.
• Protons and neutrons have a relative mass of one, while electrons have a mass of zero or very small.
• The mass number represents the total number of protons and neutrons in an atom.
• Protons have a positive charge, electrons have a negative charge, and neutrons have no charge.
• The atomic number represents the number of protons in an atom.
• Alkali metals (Group 1) donate one electron, while halogens (Group 7) accept one electron to achieve a full outer shell.
• Electrons fill up shells with a maximum of 2 on the first shell, 8 on the second and third shells, and 2 on the fourth shell.
• The periodic table was initially organized based on atomic weights, but later rearranged based on properties by Dmitri Mendeleev.
• The group number indicates the number of electrons in the outer shell of an atom.
• Isotopes are atoms of the same element with different numbers of neutrons.
• Metal atoms donate electrons to gain an empty outer shell, while non-metals accept electrons to gain a full outer shell.
• Electrons exist in shells or orbitals.
• Rechargeable batteries can be recharged when a supplied current causes the reverse reaction to occur.