1. Respond in writing to the following quote:
“"The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!' (I found it!) but 'That's funny...' "

2. 2.1 Real Scientific Methods
Is there really just one scientific method?

3. Scientific Methods
techniques used in science to discovery new knowledge, create new inventions, etc.
there are many different ways- and many of them are not structured procedures
Scientists must be great observers and very creative but also be prepared to make connections between what they know and what they see

4. Making Observations 2 types of info:
Quantitative-numerical (usually numbers)
Qualitative- descriptive (usually words)
System- what you are studying

5. Testing Ideas Figure out whether it is true or not Use experiments
Can kind of ideas can we test?

6. 2.2 Units of Measurement

7. Measurement Quantitative information
Need a number and a unit (most of time)
Represents a quantity
For example: 2 meters
2 is number
Meters is unit
Length is quantity
Units compare what is being measured to a defined measurement standard

8. SI Measurement Le Systeme International d’Unites : SI
System of measurement agreed on all over the world in 1960
Contains 7 base units
units are defined in terms of standards of measurement that are objects or natural occurrence that are of constant value or are easily reproducible
We still use some non-SI units

9. Important SI Base Units
Quantity
Symbol
Unit
Abbreviation
Length l
meter m
Mass
kilogram kg
Time t
second s
Temperature T
Kelvin K
Amount n
mole
mol

10. Prefixes
Prefixes are added to the base unit names to represent quantities smaller or larger M
mega
106
1,000,000
larger k
kilo
103
1,000 c
centi
10-2
1/100
smaller m
milli
10-3
1/1000 μ
micro
10-6
1/1,000,000

11. Mass Measure of the quantity of matter SI unit: kg use g a lot too
mass vs. weight
weight is the measure of gravitational pull on matter
mass does not depend on gravity
on a new planet, mass would be same but weight could change

12. Length SI unit: m use cm a lot too
km is used instead of miles for highway distances and car speeds in most countries

13. Derived SI Units come from combining base units
combine using multiplication or division
Example: Area: A = length x width
= m x m
= m2

14. Volume amount of space occupied by object SI: m3 = m x m x m
use cm3 in lab a lot
non-SI:
1 liter = 1000cm3 = 1000mL

15. Density ratio of mass to volume SI:
characteristic property of substance (doesn’t change with amount ) because as volume increases, mass also increases
density usually decreases as T increases
exception: ice is less dense than liquid water so it floats

16. Example
A sample of aluminum metal has a mass of 8.4 g. The volume is 3.1 cm3. Find the density.
Known
Unknown
m = 8.4 g
D = ?
V = 3.1 cm3

17. Conversion Factors
ratio that comes from a statement of equality between 2 different units
every conversion factor is equal to 1
Example:
statement of equality
conversion factor

18. Conversion Factors
can be multiplied by other numbers without changing the value of the number
since you are just multiplying by 1

19. Guidelines for Conversions
always consider what unit you are starting and ending with
if you aren’t sure what steps to take, write down all the info you know about the start and end unit to find a connection
always begin with the number and unit you are given with a 1 below it
always cancel units as you go
the larger unit in the conversion factor should usually have a one next to it

20. Example 1 Must use m as an intermediate Convert 5.2 cm to mm
Known: 100 cm = 1 m
1000 mm = 1 m
Must use m as an intermediate

21. Example 2 Must use g as an intermediate Convert 0.020 kg to mg
Known: 1 kg = 1000 g
1000 mg = 1 g
Must use g as an intermediate

22. Example 3 Must use g as an intermediate Convert 500,000 μg to kg
Known: 1,000,000 μg = 1 g
1 kg = 1000 g
Must use g as an intermediate

23. Advanced Conversions
One difficult type of conversion deals with squared or cubed units
Be sure to square or cube the conversion factor you are using to cancel all the units
If you tend to forget to square or cube the number in the conversion factor, try rewriting the conversion factor instead of just using the exponent

24. Example Convert: 2000 cm3 to m3 Known: 100 cm = 1 m
No intermediate needed
Known:
100 cm = 1 m
cm3 = cm x cm x cm
m3 = m x m x m OR

25. Advanced Conversions
Another difficult type of conversion deals units that are fractions themselves
Be sure convert one unit at a time; don’t try to do both at once
Work on the unit on top first; then work on the unit on the bottom
Setup your work the exact same way

26. Example Convert: Known: 350 g/mL to kg/L 1000 g = 1 kg
No intermediate needed
Known:
1000 g = 1 kg
1000 mL = 1 L OR

27. Combination Example Convert: 7634 mg/m3 to Mg/L Known: 100 cm = 1 m
1000 mg = 1 g 1 cm3 = 1 mL 1,000,000 g = 1 Mg mL = 1 L

28. 2.3 Using Scientific Measurements

29. Accuracy vs. Precision
Accuracy- closeness of measurement to correct or accepted value
Precision- closeness of a set of measurements

30. Accuracy vs. Precision

31. Percent Error vs. Percent Difference
Measures the accuracy of an experiment
Can have + or – value

32. Example
Measured density from lab experiment is 1.40 g/mL. The correct density is 1.36 g/mL.
Find the percent error.

33. Significant Figures
All certain digits plus one estimated digit

34. Determining Number of Sig Figs
All non-zero numbers are sig figs
Zeros depend on location in number:
LEADING zeros never count
EMBEDDED zeros always count
TRAILING zeros only count if
there is a point.

35. Location of Zeros EMBEDDED: between non-zero numbers
All are sig figs
LEADING: at front of all non-zero numbers
None are sig figs
TRAILING: at the end of non-zero numbers
If there is a decimal, all are sig figs
If there is not, none are sig figs

36. Practice 101.02 IMBEDDED 5 20.0 TRAILING w/ 3 0.005302 LEADING 4
TRAILING w/o 2
TRAILING w/ 4

37. Rounding Need to use rounding to write a calculation correctly
Calculator gives you lots of insignificant figures and you must round to the right place
When rounding, look at the digit after the one you can keep
Greater than or equal to 5, round up
Less than 5, keep the same

38. Examples Make the following have 3 sig figs: 761.50  762
 762
 14.3
 10.4
 10800
 8020
 204

39. Using Sig Figs in Calculations
Adding/Subtracting:
end with the least number of decimal places

40. Using Sig Figs in Calculations
Adding/Subtracting:
end with the least number of decimal places

41. Using Sig Figs in Calculations
Multiplying/Dividing:
end with the least number of sig figs

42. Using Sig Figs in Calculations
Multiplying/Dividing:
end with the least number of sig figs