Chemistry paper 1 higher

• Solids have a very thick structure that atoms can wiggle a little bit but are in fixed positions, there is some movement and vibration but they do not flow and cannot be compressed
• Liquids have much more movement of atoms but they are not in fixed positions, they can flow but cannot be compressed
• Gases have a lot of movement, the atoms are not in fixed positions, they can flow and can be compressed
• Energy is required to change from a solid to a liquid or liquid to gas, energy is released when changing from gas to liquid or liquid to solid
• Melting point


  The temperature at which a solid turns into a liquid
• Boiling point


  The temperature at which a liquid turns into a gas
• If a liquid and solid or liquid and gas are mixed, you will see bubbles or a loss of mass
• The plum pudding model of the atom was replaced by Rutherford's discovery of the nucleus and Bohr's development of the current atomic model
• Rutherford discovered the nucleus and protons, Chadwick discovered neutrons
• Atomic structure


  Electrons in shells around the nucleus, protons and neutrons in the nucleus
• Mass number


  Number of protons plus neutrons in an atom
• Isotopes have the same atomic number but different mass numbers
• The periodic table lists all known elements, with their atomic number, mass number, and other properties
• Relative formula mass (Mr)


  The sum of the relative atomic masses of the elements in a compound
• Empirical formula


  The simplest whole number ratio of atoms of each element in a compound
• The mass of an element on the periodic table represents the average mass of all its naturally occurring isotopes
• Element


  A pure substance made of only one type of atom
• Compound


  A substance made of two or more different elements chemically bonded together
• Mixture


  A physical combination of two or more substances that are not chemically bonded
• Separation techniques


  1. Distillation

  2. Evaporation

  3. Filtration

  4. Fractional distillation

  5. Chromatography
• For chromatography, the start line should be drawn in pencil, not pen
• Rf value


  The distance moved by a spot divided by the distance moved by the solvent
• Melting point test


  Heating a pure substance in a capillary tube and observing the temperature at which it melts
• Groups


  Vertical columns in the periodic table, indicate number of outer shell electrons
• Periods


  Horizontal rows in the periodic table, indicate number of electron shells
• Electronic configuration


  The arrangement of electrons in an atom's shells
• Metals lose electrons to form positive ions, nonmetals gain electrons to form negative ions
• Ionic bonding


  The transfer of electrons from a metal to a nonmetal
• Sodium has 11 protons and 11 electrons, the charges cancel out so it is neutral overall
• Oxygen


  In group six, has six electrons on its outer shell
• Ionic bonding


  1. Oxygen keeps the electrons it already had, electrons from magnesium are transferred to oxygen

  2. Draw square brackets around the ions and indicate the charge
• Sodium


  Atomic number 11, has 11 protons and 11 electrons, overall charge is 0
• Sodium ion


  Has lost one electron, has one more proton than electrons, has an overall positive charge
• Ionic bonding


  Forms a massive lattice, not just one-to-one bonding
• Properties of ionic compounds

  • High melting point, high boiling point, only conduct when molten or dissolved
• Covalent bonding


  Sharing of electrons between two nonmetals
• Drawing covalent compounds


  Give name, formula, draw lines for bonds, draw dot-cross diagram
• Properties of simple covalent compounds

  • Low melting and boiling points, generally gases or liquids at room temperature, do not conduct electricity
• Properties of giant covalent compounds

  • High melting and boiling points, do not conduct, do not dissolve
• Polymers


  Polymers with cross-links are fixed in place and burn, polymers without cross-links can slide and melt