Mid-Year Review

Chemistry, Earth History, Infectious Disease, & lithosphere

Chemistry- 8.P.1- Understand the properties of matter and changes that occur when matter interacts in an open and closed container.

-Physical and Chemical Properties:

  • Physical properties: A property That can be observed or measured without changing it. For example; Odor, Mass, Volume, color, density, and state. All of those things can be judged by just observing it without changing it.
  • Chemical properties: These properties can only be observed during a chemical reaction. It describes matter based on its ability to change into new matter with different properties. Examples of these are; flammability, Reactivity, and Toxicity. See all of these thing's can only be found out by changing the matter.

-Physical and chemical change:

  • Physical change: A change to a material that does not form it into a new substance. Like if you take a gold nugget and turn it into a gold ring it is still the same piece of gold but is now different than its original form.
  • Chemical change: One or more substances are changed into new substances that have new and different properties. Like if you burn a piece of paper it is no longer a that piece of paper it is now ashes and cannot be turned back.

-Elements, compounds, and, mixtures.

  • Elements: They are the basic materials made of matter. They are the things on the periodic table that are broken down to the furthest extent. Like Gold for example. They are the singular atoms

*atoms are the smallest singular things. They are made of Electron's, Proton's, and neutron's. for more see "Atomic Number, Atomic Mass, Protons, Neutrons, and Electrons" down below.

  • Compounds: Compounds are two or more Elements fused together making a molecule. The Compounds are shown with a sentence of sorts, like na2co3 which is salt.
  • Mixtures: Mixtures are two elements and/or compounds that are mixed together (hence the name). They are not fused together like compounds. They can be separated. Like gravel, you can separate them into their kinds.

- Periodic table: The periodic table is the table that shows all of the Elements.

  1. organized by Periods and groups.

  • Periods: Are horizontal columns on the periodic table. All of the elements on each period have The same amount of electron shells.

*The atoms have multiple shells that hold their electrons in certain amounts. The first shell can hold 2 electrons, the next can hold 8, the next 18 and so on and so on. So All the elements on the first Period have only the first shell. The elements on the second period need the extra shell to hold their extra electrons so they have two shells.

  • Groups: Are vertical columns on the periodic table. All of the elements on each group have the same amount of valence electrons. So the elements on the far left group are not very reactive because of their lack of valence electrons only having one, then the next has two, ect. Then at the very end are the ones that are not reactive at all having no space left.

*Valence electrons: They are the electrons in the outer shell of the atom. If A atom has few valence electrons then it is reactive (open for other electrons to come in, It has the extra space) if it has a lot than its not very reactive.

2. Metals, Non-Metals, and Metalloids

  • Metals: Obviously this is the metals on the periodic table. They are solid, shiny, good conductors of electricity and heat, and they can lose electrons rather easily.
  • Non-Metals: Non-Metals are the opposite of metals (hence the name). They are brittle, non malleable, cant conduct electricity or heat well, They gain electrons in a chemical reaction. Some are liquids.
  • Metalloids: They are somehow a cross between metals and non-metals. They partly conduct electricity and heat.

3. Atomic Number, Atomic Mass, Protons, Neutrons, and Electrons

  • Atomic Number: It shows how many proton's and Electrons are in the atom.
  • Atomic Mass: It show the sum of the protons and neutrons in an atom.
  • Protons: The positively charged parts of an atom.
  • Neutrons: The Neutrally charged parts of an atom.
  • Electrons: The negatively charged parts of an atom.

-Law of conservation of mass: This law states that matter cannot be created or destroyed. So no matter if you conduct a physical or chemical change, the outcome will always have the same mass of what you started with.


  • Matter: Anything that has mass and takes up space, This includes solids liquid and gas.
  • Solution: A substance made as a result of mixing a solid and liquid and the solid dissolves.

Earth History

Law of superposition: This law states that the layers of undisturbed earth are in order from oldest to youngest form bottom to top, because the new layers land on top.

-Index fossils:

-Ice Cores:

-Geologic time scale:

-Relative and absolute dating:

  • Relative dating:
  • Absolute dating:

- Half-life/Radioactive Decay: