1. Measurements
Chapter 2

2. Conversions Quantity English unit abb SI unit Definition
mass
Pounds
ounces
lbs oz
gram g
amount of matter in an object
volume
Gallon
quart
gal qt
liter L
amount of space an object occupies
length
Inches, feet
Yards, miles
in ft yd mi
meter m
distance between two objects
time
seconds Hr S
min
Seconds s
finite duration
temperature
Fahrenheit ºF
Kelvin
Celsius K ºC
how hot or cold something is
amount of
substance
N/A
mole
mol
the amount of a substance

3. Based on the Power of 10 106 M 109 G 1012 T micro 10-6 μ nano 10-9 n
King
Henry
Died By
drinking
chocolate
milk
Kilo
Hecta
Deca
base
deci
centi
milli
1000
100 10 1
0.1
0.01
0.001
10^3
10^2
10^1
10^0
10^-1
10^-2
10^-3
MEGA
106 M
micro
10-6 μ
GIGA
109 G
nano
10-9 n
TERA
1012 T
pico
10-12 p

4. Conversion Practice 3.68kg = _________g 600g = _________kg
568cm = _________m
8900mm = _______m
8700mL = _________L
m = ____mm
25mg = _________g
0.250kg = _______mg
0.101cm = ______mm
250mL = _________L

5. Answers

6. Accuracy v. Precision
Accuracy- How close a measured value agrees w/ the correct value
Precision-How close ea. Measurement agrees w/ ea. other

7. Which of the measuring devices would provide
a more accurate measurement?
Why is this one
a better device
to use for measuring?
Sec 2-3
Pg 44-57

8. Sig Figs(a) Exact Numbers: may be counted or defined.
Are absolutely accurate
People in a room.
There is some uncertainty in measurements.
Sig. Figs. Indicate the uncertainty in the measurements.
Digits believed to be correct by those that makes them
Can only report ONE estimated digit.

9. Using Scientific Measurements
Using a calibrated instrument of measure you can be certain of the accuracy of some of the digits measured.
The last digit of the measurement is however, always questionable
Excluding the last digit would be misleading
With the last digit you have some indication of the value’s likely range
Any measurement reported should consist of the certain digits plus the uncertain digit.
The last digit is uncertain, but it isn’t insignificant…

10. Sec 2-3
Pg 44-57

11. Using Scientific Measurements
Since only the significant digits are reported it is important to be able to determine all the significant digits in a measurement.
There are a set of rules that allow us to determine the significance of any figures in any measurement even if we don’t know the origin of the measurement

12. RULES FOR SIG FIGS
Zeros (0) used only to position the decimal are not significant.
 3 sig figs
23000  depends on the measurement

13. RULES FOR SIG FIGS Correct answer =15.2 cm2
2. In x/÷, an answer contains no more sig figs than the least # of sig figs used in the operation.
ie: (12.34 cm)*(1.23 cm) = cm2
Correct answer =15.2 cm2

14. RULES FOR SIG FIGS (37.24+10.3)=47.5447.5 (27.87-21.2342)=6.63586.64
In +/- the last digit retained in the answer is determined by the position of the first estimated number.
In other words
( )=47.5447.5
( )=6.63586.64

15. Measurements: Sig Figs
Only measurements are given significance.
There are some numbers that aren’t considered in terms of significance.
Conversion factors have an infinite number of significant figures (ratios of equal measures, like 1 ft/12 in or 60 sec/1 min)
Exact numbers also have an infinite number of significant figures, like 20 apples or 10 test tubes
Sec 2-3

16. Your Turn…
How many significant figures does each of the following measurements have? 2
9.0 km 1
1000 g 3
505 btu 2
sec 4
1.040 amps kg 6

17. Measurements: Sig Figs
Just because the calculated answer in your calculator has 8 digits in the answer – doesn’t mean they are all significant
Answers calculated from measurements may not be expressed with more significant digits than any of the original measure ments
Calculator answers must be rounded to reflect the least accurate measurement
Sec 2-3
Pg 44-57

18. Carry out each of the mathematical operation.
Your Turn…
Carry out each of the mathematical operation.
Calculate the area of a crystal surface that measures 1.34 m by m.
Calculate how many minutes a project took if the times spent on it each day were 92.5 min, min, 25.0 min, 45 min, and min.
Calculate how many hours the result from #2 would work out to be.
1.00 m, 291 min, 4.85 hrs

19. Your Turn…
Write the following #’s in sci notation…
3.27 x 104
32,700
1.024 x 106
1,024,000
x 10-3

20. Scientific On the Notation Calculator Sec 2-3 Pg 44-57 4.587E4/1.2E-3
On the
Calculator █
2nd function button you push before the EE button
Avoid this button like the plague
The EE button is 2nd function of the comma button
Use this button to enter a negative number
Sec 2-3
Pg 44-57

21. Derived Units
Units that are made up of 2+ basic units, ie. Velocity, force, acceleration.
Density
Amount of mass per unit volume.
D=m/v
Unites are g/cm3 or g/mL or g/L
Cm3 is a unit of volume for solids because v=l*w*h  cm*cm*cm=cm3
Example: A mL sample of ethanol has a mass of 37.32g. What is its density? (hint: denisty= mass/volume)

22. Derived Units Specific Gravity
Ratio of a substance’s density to the density of H2O
Density of degrees C
No units

23. How to: Derived Units Read problems Write formula Write variables
Plug in numbers
Solve
For example: Express the density of mercury in lb/ft3 if the density if g/cm3.

24. Your Turn…
A block of Zinc metal has the dimensions 5.0 cm X 7.0 cm X 20.0 cm, and its mass is 5.0 kg. What is the density of the Zinc metal in g/mL? Zinc’s density is 7.13 g/cm3, what is the percent error from the lab?

25. Dimensional Analysis Also called the factor label method
Easy way to convert between English and SI (metric).
Uses equivalent amounts
12 in = 1 ft = 12in/1ft
38m=______________ft.

26. More conversions length volume mass English to Metric Conversions
length
2.54cm=1in
39.37in=1m
1.609km=1mi
volume
1L=1.057qt
28.32L=1cubic foot
mass
453.6g=1lb
1g= oz
1 metric ton=1.102 standard tonnes

27. Dimensional Analysis Problems
74cm=__________in
25mL=__________tsp
50kg=__________lbs
160km=__________mi
3.6L=__________gal
500kg=__________oz
100m=__________yds

28. Dimensional Analysis Answers
29in or 2.9*101in
5.1tsp
1*102lbs
9.94*101mi
9.5*10-1gal
1.76*104oz
1.09*102yds
Example 2: 8.484*102lbs/ft3

29. % Error
%Error = (Actual-Theoretical) ___________________ * 100 Theoretical Will be Θ if the accepted value is greater. (+) if the accepted value is less.

30. Problems Express 12gal in cm3.
Suppose Mrs. Fraga’s Bentley contains a gas tank (handmade) that holds up to 16 gal of fuel. The price of gas is $0.315 per Liter (obviously not a problem). How much would Mrs. Fraga need to charge on her AmEx Platinum for one full tank of gas? Does not include tip.