1. CHAPTER 2 Measurements and Calculations
Selena Castro, Brittany Hodges, Fabliha Khurshan, Joey McCarthy, & Taneil Ruffin

2. Section 1 Scientific Method

3. Scientific Method! The Scientific Method is:
the logical method most scientists use to carry out investigations
All of the steps of the Scientific Method are:
Observing
quaLitative v. quaNtitative
Formulating Hypothesis
Testing Hypothesis
Theorizing
law (description of natural events) v. theory (explain based on science, technology, discoveries, etc.)
Conclusion
Publishing Results

5. A is a testable “if-then” statement.
Scientific Method!
A                             is a testable “if-then” statement. 

6. A hypothesis is a testable “if-then” statement.
Scientific Method!
A hypothesis is a testable “if-then” statement. 

7. Section 2 Units of Measurement

8. SI Base Units quantity- something that has magnitude, size, or amount
measurement- represents a quantity
Every measurement is a number + a unit
Le Système International d'Unités = SI
7 SI base units, non SI units still used
SI Units = standards of measurement
objects or natural phenomena that are of constant value, easy to preserve and reproduce, and practical in size. 

9. SI Base Units
How many SI base units are there? Give 3 examples including their name, abbreviation, and what they represent.

10. SI Base Units
How many SI base units are there? Give 3 examples including their name, abbreviation, and what they represent.
There are 7 SI base units. 
Meter, m, length
                  Kilogram, kg, mass
Second, s, time
Kelvin, K, temperature
Mole, mol, amount of substance
 Ampere, A, electric current
Candela, cd, luminous intensity

11. SI Base Units Mass- a measure of the quantity of matter SI unit: kg
the gram (g) and milligram (mg) are often used for smaller objects
often confused with weight
Weight- a measure of the gravitational pull of matter
Length 
measures distance
SI unit: m
for longer distances, kilometer (km) is used
for shorter distances, centimeter (cm) is used

12. SI Base Units
Give an example of when you would you use kilometers? centimeters?

13. SI Base Units
Give an example of when you would you use kilometers? centimeters?
1 km=1000 m
Kilometers are used to express longer distances. Sometimes road signs in the US use kilometers instead of miles. Most other countries use kilometers as the unit to express highway distances.
1 cm= 1/100 m
Centimeters are used to express shorter distances. You can use centimeters to measure smaller objects like pencils, books, etc.

14. SI Prefixes
Prefixes are added to the names of the SI base units to represent quantities that are larger or smaller than the base units.

15. What is the purpose of SI prefixes?

16. What is the purpose of SI prefixes?
Prefixes added to the names of SI base units are used to represent quantities that are smaller or larger than the base units.

17. Derived SI Units
Derived SI units are formed by combinations of SI units.
 produced by multiplying or dividing standard units

18. Volume Volumes of liquids and gases non SI unit is used = liters
Volume - the amount of space occupied by an object
derived SI unit = cubic meters, m3
Volumes of liquids and gases
non SI unit is used = liters

19. Density
Density - the ratio of mass to volume, or mass divided by volume
DENSITY =      MASS
                         VOLUME
D =                  M
                        V
the SI unit for density (kg/m3) is derived by the base units for 
mass (kg) and volume (m3)
Density is a characteristic physical property of a substance because it does not depend on the size of the sample. As the mass increases, the volume increases. 
As temperature increases, the density usually decreases.

20. What is the formula for density?

21. What is the formula for density?
DENSITY =      MASS
                         VOLUME
D =                  M
                        V

22. Why is the SI unit for density (kg/m3)?

23. Density Why is the SI unit for density (kg/m3)? DENSITY = MASS VOLUME
It is derived by the base units for 
mass (kg) and volume (m3)

24. Density
Example:
A sample of aluminum metal has a mass of 8.4 g. The volume is 3.1 cm3. Calculate the density of aluminum.
Given: 
mass (m) = 8.4 g
volume (V) = 3.1 cm3
Unknown: 
density (D)
DENSITY =      MASS        =        8.14 g
                        VOLUME              3.1 cm3
Density = 2.7 g/cm3
        

25. Conversion Factors
is a ratio derived from the equality between two different units that can be used to convert from one unit to another
For example, suppose you want to find out how many quarters are in a dollar:
You can derive conversion factors if you know the relationship between the unit you have and the unit you want.
Here's an example to try!

26. Deriving Conversion Factors
Express a mass of grams in milligrams and in kilograms. 

27. Deriving Conversion Factors
Express a mass of grams in milligrams 
and in kilograms. 
5712 mg
  kg

28. Using Scientific Measurements
Section 3
Using Scientific Measurements

29. Accuracy and Precision
Accuracy is how correct a measurement is whereas precision is getting a measurements in the same vicinity.
For example : 

30. Accuracy and Precision
Justin measures the width of his hand three times and ends up with the measurements 7, 7.25, and 7.5 inches. Are his measurements precise or accurate? Support your answer.

31. Accuracy and Precision
Justin measures the width of his hand three times and ends up with the measurements 7, 7.25, and 7.5 inches. Are his measurements precise or accurate? Support your answer.
His measurements are precise because they are all in the same vicinity meaning all have exactness.

32. Percent Error vs. Percent Difference
measures the accuracy of an experiment  
 Percent Error =  Accepted- Experimental  X 100%
                                     Accepted
Percent Difference:
 compares two values and measures precision
 Percent Difference =          | Value 1 - Value 2 |         X 100%
                                 Average of Value 1 and Value 2 

33. Significant Figures (addition/subtraction)
# of significant figures= # of digits in a value, excluding 0's at the beginning and end of the value
has 3 significant figures
In addition/multiplication, when calculating a value, your final value should have the same # of decimal places as the # of decimal places you are provided with
9.27 (3 sig. fig.) (4 sig. fig.) = (4 sig. fig.)
example problems  
7.4
12.53

34. Significant Figures (multiplication/division)
When you are performing multiplication and division problems, you should have the same number fo significant figures as you do in your term with the lowest number of significant figures
 2.16 * = 7.00
example problems
3.2 * 2.42
7.7
6.129 *
57.168

35. Significant Figures Practice
Solve the following using significant figures:
=             .
1.37 x 2.1 =            .
=                        .

36. Significant Figures Practice
Solve the following using significant figures:
=   
1.37 x 2.1 =    2.9  .
=   9.4 .