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

Scientists look at characteristics of matter, we call those properties. There are two ways properties can be recognized, physical or chemical. Physical properties are what you can observe without changing the composition of the substance.

Physical properties are when you use your five senses to describe something. You use how something looks, feels, sounds, smells, or tastes to characterize something.

Examples of Physical Properties

  • Color
  • Shape
  • Texture
  • Odor
  • Density
  • Mass
  • Volume
  • State of Matter

Chemical properties are when you can only observe something by changing the identity of the substance. This describes how something reacts with something else. They can only be observed during a chemical reaction.

Examples of Chemical Properties

  • Flammability= a substance's ability to burn.
  • Reactivity= a substance's ability to chemically bond with another substance.
  • Oxidation= when substance's chemically react with oxygen.
  • Toxicity= a substance's ability to damage an organism.
Physical and Chemical Change

Matter can't be created or destroyed, but matter can be changed. Matter changes physically or chemically. A physical change is any that doesn't involve a change in the substance's chemical identity. It does not form a new substance. Usually, physical changes can be reversed. A chemical change is any change in matter that results in the formation of a new chemical substance. One or more substances are changed into new substances that have new and different properties. Chemical change can't be reversed. A new substance is formed as a result of chemical reaction. Such as a change in color, temperature, formation of a gas,

Examples of Physical Change

  • Melting ice
  • Heating water
  • Dissolving sugar and water
  • Breaking a glass

Examples of Chemical Change

  • Color changes
  • Temperature changes
  • Formation of a gas
  • Formation of Precipitate

Elements, Compounds, and Mixtures


They are building blocks of matter made up of atoms. They are pure substances and cannot be separated into substance by chemical or physical means. They are made of one type of atom. Some examples of elements are oxygen, gold, titanium, nitrogen, sodium, and hydrogen.


They are substances formed when two or more elements chemically combine. They are made of two or more atoms of different elements. They can only be separated by chemical means, not physical. Examples of compounds are H20, C6H12O2, and NaCI. Those are examples of chemical formulas.


They are a combination of two or more pure substances that are held together by physical forces, not chemical. They are not pure and no chemical change takes place. There is a random composition and they can be separated physically. Examples of mixtures are a bowl of cereal or lemonade. There are two types of mixtures, heterogeneous and homogeneous. Heterogeneous is when you can see the individual parts and they are easily separated, take sand and pebbles for example. Homogeneous is when you can't see individual parts and there is one result.

Periodic Table

The periodic table is made up of metals, metalloids, and non-metals. The periodic table is organized by the atomic number increasing. Groups vertically organize the atoms in columns while the periods go horizontal. On the periodic table from left to right, it goes from reactive to less reactive. These arrangements are important because the elements in each period or group have similar properties. The column all the way to the right is called noble gases and they are completely unreactive.

Metals are to the left side of the periodic table. Metalloids are located on the middle of the periodic table. Nonmetals are located to the right side. The left side of the table has elements with the greatest metallic properties, this lessens as you go further to the right of the table.

Each element is represented by 1 atom. They are organized in a certain way. The top number is the atomic number, which equals the amount of protons and electrons. The letter is the element symbol, most symbols are the first or second letter of the name. The symbol could be from the Greek name. The name on the atom is the element name which identifies the element symbol. The decimal or number at the bottom is the atomic mass. You have to find the number of neutrons by subtracting the rounded atomic mass and electrons.

Law of Conservation of Mass

The Law of Conservation of Mass states that matter cannot be created nor destroyed; it can only be transferred from state to state.



Earth History

Law of Superposition

The Law of Superposition is a form of relative dating. It states that in layers of rock, the oldest layer is at the bottom while the youngest is at the top. Many scientists use this when they are searching for the relative dating of a fossil.

Index Fossils

Fossils that can be compared with each other to help identify specific periods of geologic time. This is another example of relative dating. It doesn't give you an exact time period.

Ice Cores

A long cylinder of glacial ice that came from drilling in glaciers. Scientists look at the cores to find out the climate change over the last 100,000 years or more.

Geologic Time Scale

The geologic time scale is chronological order of Earth's existence. It is divided in eras. Eras are subdivided into periods. Periods are subdivided into epochs.

The Precambrian Era: 4.5 billion - 570 million years ago-

  • Life during the Precambrian included single-celled, and simple multi-celled organisms.

Paleozoic Era: 570