precision
how close a series of measurements is TO EACH OTHER
accuarcy
how close data is to ACCEPTED value
Error
Diff between experimental and accepted value
Percent error
Absolute value of error, divided by accepted value, times 100
- Differentiate between accuracy and precision.
Accuracy is how close data is to ACCEPTED value
Precision is how close a series of measurements is TO EACH OTHER
- Be able to calculate percent error. What is the equation for determining percent error? Provide an example of a percent error problem and include the solution.
- Be able to calculate percent error. What is the equation for determining percent error? Provide an example of a percent error problem and include the solution.
Equation: |experimental - accepted|/ accepted * 100
The density of water is known to be 4 degrees Celsius. I experimentally found the density of water to be 1.08 g/mL. What’s the percent error?
|175-180|/ 180 = 5/180 = 0.028
0.028 * 100 = …………………………. 2.8%
- How do you determine the number of significant figures when you make a measurement?
You record the measurement with the certain, given digits and estimate one extra digit.
- What are the rules for determining if a zero in a number is significant? Be able to count the number of significant figures in a number.
Significant when …
0 is between 2 nonzero digits like 4.09 and 601
At the end of a number with a decimal point like 4.0 and 3980. NOT 10
Not Significant when
Its before first non zero digit (ex: 0.0701, the 0 right before and right after decimal point dont
count)
At the end w/o decimal point like 10 or 650 and 10000
- What are the rules for determining how many significant figures should be in the answer when using addition and subtraction?
Must have the same amt of DECIMAL places as the number w/ the least decimal places
- What are the rules for determining how many significant figures should be in the answer when using multiplication and division?
Same amt of sig figs as the same number withe the LEAST AMOUNT OF SIG FIGS
- Explain how to convert numbers to and from scientific notation. Show an example:
To convert it from scientific notation you…
If the “10” has a positive exponent, move the decimal point that many places to the RIGHT and if its negative, move the decimal that many places to the LEFT.
EX: 8.8910^6 = 8890000 OR 8.8910^-6 = 0.00000889
To convert it to scientific notation you…
Move the decimal point to the left or the right to make the number less that 9.99 but greater than/equal to 1
Then count the number of places you moved the decimal point and put it as the exponent (if you moved to the left, then its negative exponent, if you moved the decimal to right, its positive exponent)
EX: 9,809,000 = 9.809 10^6 OR 0.00000000000035 = 3.510^-13
- Draw and fill in a King Henry Slider for converting within a metric system.
KING : Kilo : kg
HENRY : hecto : hg
DIED : Deka : Dg
BY : Base : g
DRINKING : Deci : dg
CHOC. : Centi : cg
MILK : milli : mg
- Describe the steps to using dimensional analysis to convert between units.
- Identify the GIVEN units and NEEDED units
- Write the GIVEN unit as a numerator and denominator as 1
- Write equivalents and conversion factors for the 2 units (given & needed)
- Write the conversion factors so GIVEN units are CANCELLED and NEEDED units REMAIN
- Multiply across bottom and top
- Round to appropriate number of significant figures
- What is the equation for calculating density?
D = M/V (also remember density triangle…. M = DV and V = m/d)
Accepted value
Standard “true” value for something like freezing temp of water is 0 degrees Celsius
Experimental value
Value you get when your doing the experiment. Like you got the freezing temp of water is 0.0001 degrees celsius
Significant figures
Way to make sure numbers are as precise as possible
Scientific notation
Its an easier way to look at very large/small numbers
International System of Units
Measurement system used by most scientists & engineers
Temperature
Measure of average kinetic energy of particles in matter
Conversion factor
Fraction made from equivalency ; 12 in / 1 ft; can be inverted
English system
What the US used (inches, feet, miles) not very easy to convert
Kelvin scale
Based on molecular motion created by Lord Kelvin
Derived quantities
Quantities calculated from +2 measurements
