1. Metric Measurement

2. The Metric System Created by French scientists in the late 1700’s
Goal of the system was to create a system of measurement that was based on the decimal instead of fractions.
Single unifying system used throughout the world.
Only country that does not use the metric system as a basic unit of measurement is the United States.

3. Basic Units and Quantities
Quantity Measured
Unit
Symbol
Relationship
Length, width, distance, thickness, girth, etc. . .
millimeter
centimeter
meter
kilometer mm cm m km
10 mm = 1 cm
100 cm = 1 m
1 km = 1000 m
Mass
(not weight!)
milligram
gram
kilogram
metric ton mg g kg t
1000 mg = 1 g
1 kg = 1000 g
1 t = 1000 kg
Time
second s
60 s = 1 min
60 min = 1 hr
Temperature
degrees Celsius °C
Volume
milliliter
cubic centimeter
liter
cubic meter mL
cm3 L m3
1000 mL = 1 L
1 cm3 = 1 mL
1000 L = 1 m3

4. Basic Units and Quantities (cont’d)
Quantitiy Measured
Unit
Symbol
Relationship
Speed, velocity
meter per second
kilometer per hour
m/s
km/h
1 km/h = m/s
Density
kilogram per cubic meter
gram per milliliter
kg/m3
g/mL
Force
Newton N
1 N = (1 kg m)/s2
Pressure, Stress
kilopascal
kPa
Power
watt
kilowatt W kW
1 kW = 1000 W
Energy
joule
kilojoule
megajoule
kilowatt hour J kJ
MJ kWh
1 kJ = 1000 J
1 MJ = 1000 kJ
1 kWh = 3.6 MJ
Electric Current
ampere A

5. Precision in Measurement
When we measure, we always add one digit BEYOND the last known measurable digit
-- That digit is called the first uncertain digit
FOR EXAMPLE:
On the ruler above, the arrow is pointing between 2.4 and 2.5 cm cm is the last known digit. We also must add the first uncertain digit to show that our measurement is greater than 2.4, but less than 2.5 cm.
Therefore, the most correct measurement would be something like 2.46 cm

6. Metric Prefixes T tera 1012 1 000 000 000 000 trillion
G giga billion
M mega million
k kilo thousand
h hecto hundred
da (D) deka ten
d deci tenth
c centi hundredth
m milli thousandth
μ micro millionth
n nano billionth
p pico trillionth

7. Measuring Length, Height, Width, Etc. . .
When measuring length in science, we always use variations of the metric unit of measurement, the meter
If our measurements are too small for the meter, (like the length of a pencil), we use variations of the meter, like centimeter or millimeter
If our measurements are too large for the meter (like distances traveled), we use larger variations of the meter, like kilometer

8. Instruments Used to Measure Length, Height, Width, Etc. . .
In science, there are two basic instruments used to measure length
For large objects, we use meter sticks
For medium-sized objects, we use rulers
-- make sure to use the cm side!!!

9. Measuring Mass
When we measure mass in science, we always use variations of the metric unit for mass, which is the gram
For very large objects with lots of mass (like cars), we would use the kilogram (1000 g).
-- A lot of later formulas are based off of the kilogram, so be careful which unit you need!

10. Instruments Used to Measure Mass
Normally, triple beam balances are sufficient to find mass of most objects, however, they are NOT very accurate for small objects
INSTEAD
We prefer to use the electronic balances, which give mass in grams and are very accurate
-- You must remember to zero (tare) the electric balance AFTER you have placed the plastic measurement tray on!

11. Measuring Time
Time measurements are the same for both English and Metric Systems
Seconds, minutes, hours, days, etc.
Seconds can be further broken down using our prefixes; milli, micro, nano, femto
There are a variety of timers and stopwatches
that we will use to measure the passage
of time

12. Measuring Temperature
The metric units of temperature are the Celsius scale and the Kelvin scale
Celsius is the more commonly use
The Kelvin scale is also known as the absolute scale
0 K is as cold as anything can every be
We will talk about temperature more later in the year
Temperature measurements are made with thermometers

13. Measuring Volume
We measure volume in science using variations of the metric unit for volume, the cubic centimeter (cm3)
You must remember that 1 cm3 is EXACTLY EQUAL to 1 milliliter (mL).  This comes from water’s special definition (more on this later)
Usually, when we report volume, we report it in mL, however, for large volumes, we use the liter (1000mL).

14. Instruments Used to Measure Volume of Liquids (and some solids)
It’s pretty simple: The ONLY WAY to accurately measure volume is with a graduated cylinder***
Always read the measurement from the bottom of the meniscus
-- DO NOT use a beaker
-- DO NOT use an Erlenmeyer flask

15. Meniscus

16. Other Ways to Measure Volume
If an object is a perfect cube, we can calculate it’s volume using a simple mathematical formula:
Volume = length x width x height, or V = lwh
For instance, if we measure a small cube, with sides of cm each, we can easily calculate its volume:
L = 2 cm
H = 2 cm
W = 2 cm
V = 2 cm x 2 cm x 2 cm = 8 cm3
2 cm
2 cm
2 cm

17. Measuring Volume of Non-Cube Shaped Solids
If we want to measure volume of unusually-shaped solids, we use what is called the water displacement method.
Steps to the Water Displacement Method:
Fill a large graduated cylinder with a known volume of water. Write this value down as Volume 1.
Place the object in the graduated cylinder until it is completely submerged.
Record the new volume of water in the graduated cylinder. Write down this value at Volume 2.
Volume 2 – Volume 1 = Volume of the solid, since you didn’t add any water to the cylinder!
Try It!

18. What is the volume of the stone?
Measure the initial volume
Click for volume
200 mL
Click to place the stone in the graduated cylinder
-Now measure the new volume
Click for volume
280 mL
The volume of the stone is the difference between the 2
280 mL – 200 mL = 80 mL stone!
Click for the answer

19. Metric Conversions
Because the metric system is decimal-based, it is very easy to convert between similar metric amounts (like from centimeters to kilometers)
The only trick in moving from one metric level of measurement is knowing which way to move the decimal point (right or left)
REMEMBER, when going from bigger units to smaller units, your number should always increase (you need more smaller units to fit into one bigger unit)
The easiest method to remember is to use the METRIC STAIRS

20. The Metric Stairs kilo hecto deka deci centi milli
When moving from bigger to smaller units (left to right), we move our decimal one space to the right for each step down (our amount will get bigger!)
When moving from smaller to bigger units (right to left), we move our decimal one space to the left for each step up (our amount will get smaller!)

21. Convert 12 kg to decigrams Dg dg hg kg g
Click to convert

22. Convert 350 cm to meters
3 5 0 dm cm m
Click to convert

23. Practice Using the Metric Stairs
How many millimeters are in 24 decimeters?
How many kilograms are in centigrams?
How many liters are in 59 hectoliters?
How many kilometers will you have run if you run mm?
Click for answer
2400 mm
Click for answer kg
Click for answer
5900 L
Click for answer
.55 km

24. Things to remember
The short forms for metric units are called symbols, NOT abbreviations
Metric symbols never end with a period unless they are the last word in a sentence.
RIGHT: 20 mm, 10 kg
WRONG: 20 mm., 10 kg.
Metric symbols should be preceded by digits and a space must separate the digits from the symbols
RIGHT: the box was 2 m wide
WRONG: the box was 2m wide

25. Things to remember Symbols are always written in the singular form
RIGHT: 500 hL, 43 kg
WRONG: 500 hLs, 43 kgs
BUT: It is correct to pluralize the written out metric unit names: 500 hectoliters, 43 kilograms
The compound symbols must be written out with the appropriate mathematical sign included
RIGHT: 30 km/h, 12 cm/s
WRONG: 30 kmph, 30 kph (do NOT use a p to symbolize “per”)
BUT: It is ok to write out “kilometers per hour”

26. Things to remember Final Questions
The meaning of a metric symbol is different depending on if it is lowercase or capitalized
mm is millimeters (1/1000 meters)
Mm is Megameters (1 million meters)
Final Questions

27. Question 1
What would the best units be to measure the mass of a horse?
What about a paperclip?
Answer
Kilograms
Answer
grams

28. Question 2
Why would it be better to measure the volume of a sphere with water displacement rather than with a calculation?
You would be able to get a more accurate reading using water displacement than if you tried to find the diameter of the sphere and calculate the volume
Answer
Remember to write out 2-5 questions about the notes for class!!