Download 9th GRADE CHEMISTRY FINAL STUDY GUIDE

9th GRADE MID-TERM STUDY GUIDE
General Information
Scientific method – know steps and vocabulary
Metric system – know prefixes and conversion
Lab Safety – know names and uses of equipment and safety procedures
Matter – all matter can be classified as a mixture or a pure substance.
Matter – anything that has mass and takes up space
Mixtures – contain more than one type of matter
Homogeneous mixture – the same throughout (ex – unopened soda can)
Heterogeneous mixture – different throughout (ex – chicken noodle soup)
Substances – cannot be separated by normal physical means
Elements – contain only one type of atom (ex – copper)
Atom – the simplest part of an element.
Compounds – contain two or more atoms chemically combined (ex – NaCl / Salt)
Molecule – the simplest part of a compound.
Volume of a cube or rectangle = length X width X height
Volume of an irregular object = found by displacement method
Changes in matter:
Boiling – change of state from a liquid to a gas throughout the liquid
Evaporation – change of state from a liquid to a gas, only at the surface
Condensation – change from a gas to a liquid
Freezing – from a liquid to a solid
Sublimation – from a solid to a gas, or from a gas to a solid
Solids – molecules/atoms are close together. Shape remains the same.
Liquids – molecules/atoms can slide past one another. Take shape of their container.
Gases – molecules/atoms move freely. Take shape AND volume of container.
Properties of matter:
Density – relationship b/t mass and vol. (D = M/V). Tells how much matter is in a certain space.
Density of liquids – atoms in liquids take up more space than atoms in solids (atoms in solids are more neatly
organized). The exception is water, which actually takes up more space when frozen. Because of this,
liquids tend to be LESS dense than their solid counterparts.
Viscosity – a material’s resistance to flow (ie – how thick a substance is). Ex – honey is more viscous than
water. Heating a substance will make it less viscous (less thick).
Atoms & Elements
Atoms – are made of protons, neutrons, and electrons.
Protons – have a mass of 1 AMU (atomic mass unit). Found in the nucleus. Have a positive charge.
Neutrons – have a mass of 1 AMU. Found in nucleus. No charge (neutral).
Electrons – have almost zero mass. Found outside the nucleus. Negative Charge.
Subatomic particles – the collective name for protons, neutrons and electrons, because they are smaller than
atoms.
Atomic Number – number of protons in an atom. This is what makes each element different.
Atomic mass – average mass of all isotopes of an atom.
Isotope – different atoms of the same element may have different numbers of neutrons (protons, however,
will ALWAYS be the same).
Ion – at atom that has gained or lost electrons and now has an electrical charge.
Mass number – protons + neutrons. This is the weight on the atom.
Electrons are arranged in energy levels around the nucleus.
The first energy level holds only 2 electrons. The subsequent energy levels hold varying numbers.
Valence electrons – electrons in the outermost energy level (8 is the maximum number).
Octet Rule – all atoms wish to have a full valence shell (8 for most atoms), this is why they react with other
elements.
Periods – the rows of the periodic table (tells you how many energy levels are present).
Groups or families – the columns of the periodic table. Can tell you how many valence electrons.
Chemical bonding
Ionic bonds – involve the gaining or losing of electrons (ex – Na gives an electron to Cl in NaCl).
Covalent bonds – involve the sharing of electrons (ex – Cl shares electrons with Cl in Cl2).
Oxidation number – tells how many electrons an element wishes to gain or lose. Positive oxidation numbers
tell us that the atom wants to give away electrons, negative oxidation numbers tell us the atom wants to
gain electrons (ex – Na1+ wants to give away one electron).
Reactants – the chemicals that go into a chemical reaction (to the left of the arrow).
Products – the chemicals that come out of a chemical reaction (to the right of the arrow).
Formula mass – the mass of one molecule of a substance (add the mass of all the atoms of the compound)
Avogadro’s number = one mole of a substance = 6.02 x 1023 molecules.
Chemical Reactions
Law of conservation of matter (conservation of atoms) – matter cannot be created or destroyed.
Balancing equations – a chemical equation must have the same number of each type of atom on the reactant
side and the product side. The equation is a recipe – you must figure out how much of each
“ingredient” is necessary.
Addition or synthesis reaction – two or more substances combine to form a compound.
Decomposition reaction – a single compound is broken apart to form two or more smaller compounds.
Single-replacement (displacement) reaction – one element replaces a similar element in a compound.
Double replacement (displacement) reaction – two elements change places in two compounds.
Exothermic reaction – one that gives off energy (would feel hot). Ex - meal ready to eat (MRE).
Endothermic reaction – one that takes in energy (would feel cold). Ex – instant ice pack.
Strong Nuclear Force – this is the force that holds together the nucleus.