Measurement and using SI prefixes

1. MEASUREMENT IN
SCIENCE
SI Units
Metric Units
Unit Equalities
Unit Conversions

2. Measurement
• You are making a measurement when you
• Read your watch
• Check you weight
• Take your temperature
• Pour out milk for cake batter

3. StandardsofMeasurement
• When we measure, we use a measuring tool to compare some
dimension of an object to a standard.
• What tools do we use to measure?
• Thermometer
• Ruler
• Graduated cylinder
• Watch
• Scale

4. LearningCheck
• State the tool(s) you would use to measure the following:
• A. temperature
• B. volume
• C. time
• D. weight

5. Solution
• State the tool(s) you would use to measure the following:
• A. temperature: thermometer
• B. volume: measuring cup, graduated cylinder
• C. time: watch
• D. weight: scale

6. MeasurementinScience
• In science we:
• do experiments
• measure quantities
• use numbers to report measurements

7. Statinga Measurement
• In every measurement there is a:
• Number
• followed by a:
• Unit from a measuring device

8. LearningCheck
• What are some units used to
measure the following?
• length
• volume
• weight
• temperature

9. Solution
• What are some units used to
measure the following?
• Length: meters, feet, inch, km
• Volume: mL, cup, teaspoon
• Weight: pounds, grams
• Temperature: Celcius,
Farenheit

10. Units
• There are many different units, used around the world to
describe the same things.
• Scientists can still use these different units, they are still valid.
It’s just that, for the most part, they try to stick to standard
units.

11. LearningCheck
• Identify from each of the following:
• a. the unit of measurement (both the unit name and symbol)
• b. what is being measured
• The patient’s temperature is 102°C.
• The sack holds 5 lbs of potatoes.
• It is 8 kilometers from your house to school.
• The bottle holds 2 L of orange soda.

12. Solution
• Identify from each of the following:
• a. the unit of measurement (both the unit name and symbol)
• b. what is being measured
• The patient’s temperature is 102°C (Celcius, temperature).
• The sack holds 5 lbs (pounds, mass) of potatoes.
• It is 8 kilometers (km, length) from your house to school.
• The bottle holds 2 L (liters, volume) of orange soda.

13. LearningCheck
• Match the statements below with what is being measured:
1) length 2) mass 3) volume
____ A. A bag of potatoes is 5.0 lbs.
____ B. A person is 2.0 m tall.
____ C. A medication contains 0.50 g Aspirin.
____ D. A bottle contains 1.5 L of water.

14. Solution
• Match the statements below with what is being measured:
1) length 2) mass 3) volume
2 A. A bag of potatoes is 5.0 lbs.
1 B. A person is 2.0 m tall.
2 C. A medication contains 0.50 g Aspirin.
3 D. A bottle contains 1.5 L of water.

15. MetricSystem
• Is a decimal system based on 10
• Used in most of the world
• Used by scientists and hospitals
• Known as SI (systeme internationale) units

16. InternationalSystemofUnits(SI)
Quantity Unit Symbol Quantity Unit Symbol
Length metre m Resistance Ohm Ω
Mass gram g Charge Coulomb C
Volume metre cubed m3 Power Watt W
Time second s Force Newton N
Energy joule J Pressure Pascal Pa
Temperature kelvin K
Amount of
substance
mole Mol
Current ampere A Frequency Hertz Hz
Potential
Difference
Volt V
Luminous
intensity
candela cd

17. BaseUnits
• Sometimes the S.I. units are too small or too large to describe
a certain quantity.
• For example a metre would be too big to describe the size of
an atom; an atom is a very small thing.

18. MetricPrefixes
• Use prefix to increase or decrease basic unit by 10
• Form new units larger or smaller than the basic units
• Indicates a numeric value
• Prefix unit = value unit
• 1 kilometer = 1000 meters
• 1 kilogram = 1000 grams

19. PrefixesthatIncreaseAUnit
Prefix Symbol Value
Giga G 1 000 000 000
Mega M 1 000 000
Kilo k 1 000
Where have you seen these prefixes written before?

20. PrefixesthatDecreaseAUnit
Prefix Symbol Value
deci d 0.1
centi c 0.01
milli m 0.001
micro  0.000 001
nano n 0.000 000 001

21. Justhowsmallisananometre?
21

22. UnitScale

23. LearningCheck
Select the unit you would use to measure:
1.Your height
a) millimeters b) meters c) kilometers
2.Your mass
a) milligrams b) grams c) kilograms
3.The distance between two cities
a) millimeters b) meters c) kilometers
4.The width of an artery
a) millimeters b) meters c) kilometers

24. Solution
Select the unit you would use to measure:
1.Your height
a) millimeters b) meters c) kilometers
2.Your mass
a) milligrams b) grams c) kilograms
3.The distance between two cities
a) millimeters b) meters c) kilometers
4.The width of an artery
a) millimeters b) meters c) kilometers

25. LearningCheck
Indicate the prefix to use for:
1. A mass that is 1000 times greater than 1 gram
a) kilo b) milli c) mega
2. A length that is 1/100 of 1 meter?
a) deci b) centi c) milli
3. A unit of time that is 1/1000 of a second.
a) nanosecond b) microsecond c) millisecond

26. LearningCheck
Indicate the prefix to use for:
1. A mass that is 1000 times greater than 1 gram
a) kilo b) milli c) mega
2. A length that is 1/100 of 1 meter?
a) deci b) centi c) milli
3. A unit of time that is 1/1000 of a second.
a) nanosecond b) microsecond c) millisecond

27. Equalities
• State the same measurement using two different units
• Example: Describe the length of the line below in two different
ways
• 10.0 in.
• 25.4 cm

28. SomeMetricEqualities
• Length: 1 m = 100 cm
• Mass: 1 kg = 1000 g
• Volume: 1 L = 1000 mL

29. LearningCheck
1. 1000 m = 1
a) mm b) km c) dm
2. 0.001 g = 1
a) mg b) kg c) dg
3. 0.1 L = 1
a) mL b) cL c) dL
4. 0.01 m = 1
a) mm b) cm c) dm

30. Solution
1. 1000 m = 1
a) mm b) km c) dm
2. 0.001 g = 1
a) mg b) kg c) dg
3. 0.1 L = 1
a) mL b) cL c) dL
4. 0.01 m = 1
a) mm b) cm c) dm

31. LearningCheck
Give the value of the following units:
1. 1 kg = ____ g
a) 10 g b) 100 g c) 1000 g
2. 1 mm = ____ m
a) 0.001 m b) 0.01 m c) 0.1 m

32. Solution
Give the value of the following units:
1. 1 kg = ____ g
a) 10 g b) 100 g c) 1000 g
2. 1 mm = ____ m
a) 0.001 m b) 0.01 m c) 0.1 m

33. ConversionFactors
• Fractions in which the numerator and denominator are
quantities expressed in an equality between those units
Example: 1 in. = 2.54 cm
Factors: 1 in. and 2.54 cm
2.54 cm 1 in

34. LearningCheck
• Write conversion factors that relate each of the following pairs
of units:
A. Liters and mL
B. Meters and kilometers

35. Solution
• Write conversion factors that relate each of the following pairs
of units:
A. Liters and mL: 1 L = 1000 mL
1L and 1000 mL
1000 mL 1L
B. Meters and kilometers: 1000 m = 1 km
1000 m and 1 km
1 km 1000 m

36. LearningCheck
• Sometimes if you don’t know the conversion factor
immediately, do it in 2 smaller steps
• Write conversion factors that relate each of the following pairs
of units:
C. Kilograms and milligrams
D. Hours and seconds

37. Solution
• Sometimes if you don’t know the conversion factor
immediately, do it in 2 smaller steps (dimensional analysis)
• Write conversion factors that relate each of the following pairs
of units:
C. Kilograms and milligrams
1 kg x 1g = 1 kg
1000 g 1000 mg 1000 000 g
D. Hours and seconds
1h x 1 min = 1 h
60 min 60 s 3600 s

38. LearningCheck
• A rattlesnake is 2.44 m long. How long is the snake in cm?
a) 2440 cm
b) 244 cm
c) 24.4 cm

39. Solution
• A rattlesnake is 2.44 m long. How long is the snake in cm?
a) 2440 cm
b) 244 cm
c) 24.4 cm
2.44 m x 100 cm = 244 cm
1m

40. UnitCheck
• What is wrong with the following setup?
1.4 day x 1 day x 60 min x 60 sec
24 hr 1 hr 1 min

41. UnitCheck
• What is wrong with the following setup?
1.4 day x 1 day x 60 min x 60 sec
24 h 1 h 1 min
Units = day2
h2
Not the final unit needed

43. StepstoProblemSolving
• Read problem
• Identify data
• Write down a plan from the initial unit to the desired unit
• Select conversion factors
• Change initial unit to desired unit
• Cancel units and check
• Do math on calculator
• Give an answer using significant figures (next class!)

44. Practice Questions
• w/b page 13 , 14
• Page 17 – odd numbers