chapter2_phjn

=Chapter Two=


 * Section 1**: Scientific method
 * Section 2**: Units of measurement
 * Section 3**: Using scientific measurements

Section 1 Vocabulary:

 * __Scientific Method__** - A logical approach to solving problems by observing and collecting data, formulating hypotheses, testing hypotheses, and formulating theories that are supported by data.
 * __Hypothesis__** - A testable statement.
 * __Theory__** - A theory is a broad generalization that explains a body of known facts or phenomena.
 * __Model__** - In science a model is more than just a physical object; it is an explanation of how phenomena occur and how data or events are related.

Section 2 Vocabuary:
- An Example converting 1m3 to 1,000,000 cm3 - Quantity sought = quantity given X conversion factor.
 * __Quantity__** - Something that has magnitude, size, or amount.
 * __Volume__** - The amount of space occupied by an object.
 * __Density__** - Is the ratio of mass to volume, or mass divided by volume.
 * __Dimensional Analysis__** - A mathematical technique that allows you to use units to solve problems involving measurements.
 * __Conversion Factor__** - A ratio derived from the equality between two different units that can be used to convert from one unit to the other.

Section 3 Vocabulary:

 * __Accuracy__** - Refers to the closeness of measurements to the correct or accepted value of the quantity measured.
 * __Precision__** - Refers to the closeness of a set of measurements of the same quantity made in the same way.
 * __Percentage error__** - It’s calculated by subtracting the accepted value from the experimental value, dividing the difference by the accepted value, and then multiplying by 100.

Example problem:
Example for Percentage error: You do an experiment and find out that atomic weight for helium is 4.1 here you can see this is not correct by using the percent error equation.

**Significant figures:**
- In a measurement consisting of all the digits known with certainty plus one final digit, which is somewhat uncertain or is estimated.

Rules:
1. Zeros appearing between nonzero digits are significant. 2. Zeros appearing in front of all nonzero digits are not significant. 3. Zeros at the end of a number and to the right of a decimal point are significant. 4. Zeros at the end of a number but to the left of a decimal point may or may not be significant. If a zero has not been measured or estimated but is just a placeholder, it is not significant. A decimal point placed after zeros indicates that they are significant.

//When adding or subtracting decimals, the answer must have the same number of digits to the right of the decimal point as there are in the measurement having the fewest digits to the right of the decimal point.//
 * HINT:**

Ex: 65000 km into scientific notation 6.5 x 104 km
 * Scientific Notation**- Numbers are written in the form M x 10^n, where the factor M is a number greater than or equal to 1 but less than 10 and n is a whole number.


 * __Direct Proportions__** - Two quantities are directly proportional to each other if dividing one by the other gives a constant value.
 * __Inverse Proportions__** - Two quantities are inversely proportional to each other if their product is constant.

Peter Hric Jesse Nowak Period 6 Mr. Ptachcinski