1. UNITS OF MEASUREMENT
The metric system

2. CHEMISTRY You will be studying chemistry
Chemistry is defines as “the study of matter and its reactions”
Chemistry is a physical science so we need to discuss how we measure things

3. WHAT ARE UNITS OF MEASUREMENT?
Units describe what aspect of matter is being measured
Qualitative: something that is described
Quantitative: something that is measured
Examples:
Unit of distance – mile
Unit of volume – gallon
Unit of time – hour
Unit of weight - pound

4. SI UNITS OF MEASUREMENT
SI – Standards International
Set of units that are recognized by the scientific community
In science (unlike math), you need a unit for EVERY NUMBER
These are the units we will be using in this class – not English units

5. BASE UNIT Metric system is a base 10 system
A base unit is a unit that measures some sort of physical/chemical data
Distance – meter (m)
Mass – gram (g)
Volume – liter (L)
Time – second (s)
Temperature – degrees Celsius (°C)
Energy – Joules (J)

6. MASS – A QUICK EXPLANATION
Mass and weight are different
Weight can change. It is not an absolute value
Weight depends upon the force of gravity
You weigh more on Earth than on the Moon
Mass cannot change. It is an absolute value
Mass depends on the amount of matter in a substance
Mass does not change with gravity

7. PREFIXES (GET HANDOUT)
Look at the name of the prefixes and the abbreviation on the sheet
These prefixes work for all base units
The prefix tells you how the base unit can be changed
Example:
If you have a cg (centigrams), this means that the centigram is 1/100 of a gram.
If you have a cL (centiliter), this means that the centiliter is 1/100 of a liter.

8. HOW DO WE CHANGE THE BASE UNIT?
How big the measurement is depends on the prefix from the metric system
You increase or decrease the size of the number by changing the prefix in front of the base unit
IMPORTANT NOTE:
When you go DOWN the chart, the number gets BIGGER
When you go UP the chart, the number gets SMALLER

9. STEPS TO CONVERT : EXAMPLE: 100mm = _?_cm
Step 1: Find the conversion on the last column of the handout (Look at the prefixes)
100mm = _____ cm
m (milli): 1 meter = 1000 mm
c (centi): 1 meter =100 cm
Step 2: Use the conversion from the last column to convert to the base unit. (We will use ratios)
We start with 100millimiters (mm) and we want to make it the base unit meters (m)
The base unit DOES NOT have a prefix
Therefore: 100 mm = ??? m

10. MATH FOR THE STEP 2
We look at the prefix conversion from the first step
1m = 1000mm
We start with 100mm
So the equation is:
1m____ = (x) m____
1000mm mm
Solve for x to find the number of meters
NOTE: The meters(m) are both on top and the millimeters(mm)are both on bottom

11. ANSWER FOR STEP 2
When you cross-multiply, you get the following:
x = 0.1m

12. STEPS TO CONVERT
Step 3: Use the answer that you got from step 2, to calculate into the unit you are looking for (cm)
We have our answer from step 2 (0.1m)
We want to convert it to our second unit (cm)
Therefore, we want to turn 0.1m into centimeters (cm)
We will use the other conversion from the first step
1meter (m) = 100 centimeters (cm)

13. MATH FOR STEP 3 1m = 100cm We start with 0.1m So the equation is:
1m____ = m____
100cm (x) cm
Solve for x to find the number of centimeters
NOTE: The meters(m) are both on top and the centimeters (cm) are both on bottom

14. ANSWER FOR STEP 3
When you cross-multiply, you get the following:
x = 10 cm
NOTE: I know most of you know how to move the decimal to get the answer. YOU have to do it this way for the homework and quizzes. THERE IS A REASON.

15. ONE FINAL THING
The example we just did showed how to go from to numbers with prefixes in their units mm to cm
This process involved 2 math steps
If your problem only has 1 number with a prefix, you will only need 1 math step
Example:
250 cm = ??? m

16. MATH FOR EXAMPLE
100 cm = ??? m
Find the value in the final column for centimeters (cm)
1meter (m) = 100 centimeters (cm)
Set up the ratio:
1m__ = (x) m__
100 cm cm
x = 2.5m

17. PRACTICE Try the following 3 conversions IN YOUR NOTES:
1500 g = __?__ kg
63.3 hL = __?__ mL
1.22 km = __?__ nm

18. ANSWERS
1.500 g
6,330,000 mL
1,220,000,000,000 nm

19. TRY THESE IN ON YOUR OWN 0.25 hg = ________ g 3200 cm = ________ m
kL = ________ mL
33400nJ = _______ kJ
225 dkg = ________ dg
880 hm = ________ um
1 nL = ________ kL

20. SCIENTIFIC NOTATION 13,600,000,000,000 dollars
Some numbers are so big or small that you have to write too many numbers
Scientists have a short hand way to abbreviate these number called scientific notation
Let’s look at the current national debt
13,600,000,000,000 dollars

21. FORMAT
In scientific notation we use exponents to tell us how to move the decimal
Write the number (without any zeroes before or after it)
136
Put a decimal after the first digit
1.36

22. FORMAT
Count how many spaces before or after the decimal that you need to move the decimal to get to your original number
1.36
13,600,000,000,000.
You have to move the decimal 13 spaces to the right

23. FORMAT
Use the following convention that shows you moved the decimal 13 spaces
x 1013
Put the original number from step 2 with step 4
1.36 x 1013
This tells you to move the decimal 13 places to the right

24. QUESTION How do you show that we move the decimal to the left?
For example:

25. ANSWER
Same method except you use a negative (-) number in the exponent to show that the decimal goes to the left
1.22 x 10-3
The (-)3 says to move the decimal 3 spots to the left in the number 1.22

26. TRY THESE
What are the following numbers in scientific notation?
356,000,000
What are the following numbers written out as a numeral?
2.50 x 102
7.77 x 10-3

27. ANSWER What are the following numbers in scientific notation?
3.56 x 108
1.25 x 10-5
What are the following numbers written out as a numeral?
250

28. PRACTICE WITH CALCULATORS
You will need to know how to read and enter scientific notation on calculators
After receiving a calculator, we will practice some on the board.