Chapter 2 & 3



Matter is broken down into two main parts: mixtures and pure substances.

A pure substance is something that is consistent throughout. This means that in this substance all the atoms or molecules are the same.

Mixtures are collections of more than one type of molecule and/or atom. This can include solutions, such as salt water, suspensions which tend to be cloudy, and mechanical mixtures, such as raisin bran where the parts are readily visible and can be separated.


Physical and Chemical Changes

Chemical change is any change that results in the formation of new chemical substances. At the molecular level, chemical change involves making or breaking of bonds between atoms. These changes are chemical changes: iron rusting (iron oxide forms) gasoline burning. Physical change rearranges molecules but doesn't affect their internal structures. Some examples of physical change are:

:whipping egg whites (air is forced into the fluid, but no new substance is produced) :magnetizing a compass needle (there is realignment of groups ("domains") of iron atoms, but no real change within the iron atoms themselves).

Tek: 4.A, 5.A,

Physical versus Chemical Changes

Extensive & Intensive Property.

An extensive property is a property that changes when the size of the sample changes. Examples are mass, volume, length, and total charge. An intensive property doesn't change when you take away some of the sample. Examples are temperature, color, hardness, melting point, boiling point, pressure, molecular weight, and density. Because intensive properties are sometimes characteristic of a particular material, they can be helpful as clues in identifying unknown substances.


Solid, Liquid, & Gas.

Solid - of definite shape and volume. Liquid - Having a consistency like that of water or oil, flowing freely but of constant volume. Gas - a substance such as air, which is not solid or liquid, and usually cannot be seen: The basic physical properties of gases, liquids and solids are described in terms of structure, particle movement, effects of temperature and pressure changes, and particle models used to explain these properties and characteristics.


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Unit Conversion and Dimensional Ananlysis

Dimensional analysis is a method of problem-solving that focuses on the units used to describe matter.

Example (from book)- If you want to convert a temperature in degrees Celsius to a temperature in kelvins, you focus on the relationship between the units in the two temperature scales.

Tek:2.G,8.E, the chemistry book

Scientific Notation

Scientific notation expresses numbers as a multiple of two factors: a number between 1 and 10 which is raised to a power, or exponent. A simple way to sum this up is for you to take an outrageous number like (ex. from book) 1,392,000 which would be come 1.392*10^6. What I did there was I moved the decimal to the first integer and then I counted how many spaces I moved to the left to figure out what my exponent is. It's the same thing if you moved to the right, the only difference is the exponent will be negative.

When you add or subrtract numbers written in scientific notation, you must be sure that the exponents are the same before adding or subtractiing. Suppose you have (7.35*10^2m+2.43*10^2m) all you would do is add 7.35 and 2.43 and your final answer should be (9.78*10^2m). If the exponents aren't the same you would have to find the first factor that is between 1 and 10 and use that exponent. For example (2.70*10^7+1.56*10^6+1.65*10^8), you would leave the first figure alone and change the other two. On the (1.56*10^6) you would raise the power one higher so that it equals 7. On the (1.65*10^8) you would decrease the power to 7 and move the decimal one place to the right it should now look like (1.65*10^7)+(1.65*10^7)=5.91*10^7.

When you multiply or divide you multiply or divide the first factors. Then you add or subtract the exponents. For example(2*10^3)*(3*10^2) your going to multiply 2*3 and then your going to add 3+2=5 so your answer will be 6*10^5. Another example is where you do (9*10^8)/(3*10^-4), your going to divide the 9/3=3 and then your going to subtract 8-(-4)=12 and then your final answer will be 3*10^12


Significant Figures

(From the book) A significant figure is are all the known digits plus one estimated digit. Non-zero numbers are always significant. Zeros between non-zero numbers are always significant. All final zeros to the right of the decimal place are significant. Zeros that act as placeholders are not significant. (Convert quantities to scientific notation to remove the placeholder zero.) Counting numbers and defined constants have an infinite number of significant figures.

So for 0.00040230 there would only be five significant numbers because there are three nonzero numbers, a final zero, and a zero between two non-zero numbers. The rest of the zeros are placeholders.

Tek:2.G, 8.E

Data representation

A graph is a visual display of data. People use all kinds of graphs the most common are circle graphs, bar graphs, and line graphs. When interpreting a graph you must first identify the independent and dependent variables. Look at the ranges and consider what measurements were taken. Decide if the relationship is linear or nonlinear.

Tek: 2.H, 2.I

Law of Conservation of Mass

This law states that mass is neither created nor destroyed during a chemical reaction- it is conserved.(The book) Mass(reactants)=Mass(products)

It was made by Antoine Lavoisier (1743-1704).