1. MEASUREMENT Units of Measurement : SI unit and derived units
Unit prefixes
Unit conversion using dimensional analysis
Scientific notation
Increment, Accuracy, Precision

2. OBJECTIVES Distinguish between a number and a quantity.
Name SI units for length, mass, time, temperature, volume and density.
Define and identify base units; unit conversions; identify prefixes
Perform unit conversion using dimensional analysis.

3. Units of Measurement
In our daily lives we deal with making measurements routinely.
i.e., How much gasoline is required to fill your gas tank? What time did you wake up this morning? How fast did you drive to school today ?
Doctors, nurses, pharmacists-
Doctors and nurses make measurements constantly. Measurements like pulse rate, blood pressure, temperature, drug dosage.
Math - The language of Science
Scientists make countless measurements during their experiments to prove or disprove a theory.

4. Otherwise, it is meaningless!
Units of Measurement
What is your response if I told you that:
I weigh 65
In any measurement magnitude (the number) as well as the unit (meaning) must be stated.
Otherwise, it is meaningless!

5. Number vs. Quantity
Quantity : number + unit
UNITS MATTER!!

6. Systems of Measurement
Scientific Community
What units are used?
The Rest of the
World
America
English System
1 ft = 12 in
1 yd= 3 ft
1 mi. = 1,760 Yd
1 mi = 5280 ft
Metric System
1 km = 1000 m
1 m = 100 cm
Le System
International d’Unites
SI Units are basically an
updated form of the
metric system.

7. Metric system and the Le Systeme International d'Unites (SI)
The Metric system is convenient because it uses only one fundamental unit for each type of measurement. For example for:
*Length we use only meter, in the US we use foot, yard, inch.
*Mass we use Kg not pound.
All the Prefixes are multiples of 10.

8. SI Units Quantity Symbol Base Unit Abbrev. Length l meter m Mass m
kilogram kg
Time t
second s
Temp T
kelvin K n
mol
Amount of particles
mole

9. SI Prefix Conversions
Prefix
Symbol
Factor
Giga
Mega- G
109
106
Kilo- k
103
Hecto- h
102
Deka- da 10
BASE UNIT
--- 1
deci- d
10-1
centi- ?
milli- m
10-3
micro- 
10-6

10. Derived Units: Combination of base units
Area ( m2)
length  length = m x m
Volume (m3)
length  length  length= m x m x m
D = M V
Density (g/cm3)
mass per volume

11. Temperature A measure of how hot or how cold an object is.
SI Unit: the kelvin ( K )
Note: not a degree
Absolute Zero= 0 K

12. Temperature Scales

13. Celsius and Kelvin
K= oC + 273

14. Unit conversion using dimensional analysis Page
Unit 1 - MEASUREMENT
Unit conversion using dimensional analysis
Page

15. SI Prefix Conversions To the left or right?
1. Find the difference between the exponents of the two prefixes.
2. Move the decimal that many places.
To the left
or right?

16. SI Prefix Conversions Prefix Symbol Factor Giga Mega- G 109 M Kilo- K
106
Kilo- K
103
Hecto- H
102
Deca- D 10
BASE UNIT
--- 1
move left
move right
deci- d
10-1
centi- c
10-2
milli- m
10-3
micro- 
10-6

17. SI Prefix Conversions 1) 20 cm = ___________ m
2) L = ______________ mL
3) 45 m = ______________ cm
4) 80.5 km = ______________ m

18. How would you convert 2h 45 min to second
Convert km/h to m/s

19. Converting by using Dimensional Analysis
Steps:
Identify starting ( also called given, old )&
ending ( target, new) units.
2. Line up conversion factors so units cancel.( hint : the new units should on the top)
3. Multiply all top numbers & divide by each bottom number. ( )
4. Check units & answer.

20. Converting by using Dimensional Analysis: inch to cm
Identify
10.0 in
We start by writing down the
Given (old) and its Unit

21. Converting by using Dimensional Analysis: inch to cm
Line up
10.0 in x
2.54 cm
1 in
We know 1 in = 2.54 cm. So our conversion
factor is : 1 in = 2.54 cm. Since we want to
convert to cm, it goes on the top. ( Hint)

22. Converting by using Dimensional Analysis: inch to cm
Cancel units
10.0 in x
2.54 cm
1 in
Now we cancel and collect units. The inches cancel
out, leaving us with cm : the Target unit.

23. Converting by using Dimensional Analysis: inch to cm
10.0 in x
2.54 cm
25.4 cm =
1 in
Since the unit is correct,
all is left to do the math ...
The
Answer

24. Lets check it out !!!!!!
Find the 10 in mark and directly across
at the cm side. What number do you find?

25. Converting by using Dimensional Analysis: inch to cm
You go to Europe and decide to have a haircut. Your hairdresser wants to cut your hair 8.0 cm shorter. How many inches will he be cutting off?
Identify , line up, cancel out, multiply, check
8.0 cm
1 in
2.54 cm
= ? in
Question: Is the conversion Factor the same? What’s the difference?

26. Converting by using Dimensional Analysis: g to Kg
Convert 250 g into Kg
Identify , line up, cancel out, multiply, check
250 g x 1Kg = Kg
1000 g

27. Converting by using Dimensional Analysis: Kg to g
Convert 1.5 Kg into g
Identify : Given and Target unit
Line up: Conversion Factor
1.5 kg x = g
Q: Which conversion factor will you be using?
1Kg = 1000g or 1000g= 1Kg

28. A more complex conversion
km to m
hr s
kilometers into meters and hour into second. We can do both conversions at once using the same method as in the previous conversion.

29. A more complex conversion
km to m
hr s
Identify
80 km
Write down the
_____and ____ hr

30. A more complex conversion
km to m
Line up
80 km x
hr s
1 hr hr
3600 s
First conversion factor is: 1 hour = 3600 sec.

31. A more complex conversion
km to m
Line up
80 km x
hr s
1 hr x
1000 m hr
3600 s
1 km
The second conversion factor is: 1 km = 1000 m.

32. A more complex conversion
km to m
Cancel out units
80 km x
hr s
1 hr x
1000 m m = s hr
3600 s
1 km
Check your units !!!
If you have chosen the correct conversion factors, you
should only be left with the units you want to convert to.

33. A more complex conversion
km to m
hr s
80 km x
1 hr x
1000 m = hr
3600 s
1 km
80,000 m m
The
Answer!! = s
3600 s

34. A Very more complex conversion to finish at home today !!
Problem1:Convert 1 year into seconds
year seconds 1y
= s
1 y
365 days
24h
1day
1 h
60s

35. Dimensional Analysis
Problem2: Taft football needs 550 cm for a 1st down. How many yards is this? cm yd
550 cm
= yd
1 yd
3 ft
1 in
2.54 cm
12in
1ft

36. Dimensional Analysis cm pieces 1.3 m = pieces
Problem3: A piece of wire is 1.3 m long. How many 1.5-cm pieces can be cut from this wire? cm
pieces
1.3 m
= pieces

37. Dimensional Analysis Problem5:How old are you in minutes? Age in y

38. How would you convert 2h 45 min to second
Homework
Units and Conversions HW
Due: tomorrow
How would you convert 2h 45 min to second
Convert km/h to m/s

39. M x 10n Scientific Notation M is the coefficient 1<M<10
10 is the base
n is the exponent or power of 10

40. Other Examples:
5.45E+6
5.45 x 10^6

41. Numbers less than 1 will have a negative exponent.
Numbers bigger than 1 will have a positive exponent.
A millionth of a second is:
sec
1.0E x10^-6

42. Limits of Measurement
Accuracy and Precision

43. Accuracy - a measure of how close a measurement is to the true value of the quantity being measured.

44. Example: Accuracy
Who is more accurate (Susan or Amy) when measuring a book that has a true length of 17.0cm?
Susan:
18.1cm, 16.0cm, 18.0cm, 17.1cm
Amy:
16.5cm, 16.0cm, 16.2cm, 16.3cm

45. Precision – a measure of how close a series of measurements are to one another. A measure of how exact a measurement is regardless is it is close to the real value.

46. Example: Precision
Who is more precise when measuring the same 17.0cm book?
Susan:
17.0cm, 16.0cm, 18.0cm, 15.0cm
Amy:
15.5cm, 15.0cm, 15.2cm, 15.3cm

47. Example: Evaluate whether the following are precise, accurate or both.
Not Precise
Not Accurate
Precise
Accurate
Precise

48. Graduated Cylinder - Meniscus