Biology Lesson 1.2 Measurement and Conversion
I. SI units
A. International System of Units
B. Based on units of 10
II. Standard SI units
A. length: meter: m
B. volume: cubic meter: m3
C. mass: kilogram: kg
1. mass and weight are different measurements, weight is a measure of force
2. gram is usually used because the kilogram is a lot in a lab
D. time: second: s
E. temperature: Kelvin: K
F. scientists measure temperature with Celsius and then convert to Kelvin
III. Prefixes
Prefix symbol meaning
Mega M 1,000,000
kilo- k 1000
hecto- h 100
deka- da 10
unit (meter, liter, gram)
deci- d 0.1 (1/10)
centi- c 0.01 (1/100)
milli- m 0.001 (1/1000)
micro m 0.000001 (1/1000,000)
IV. Conversions
mega
kilo
hecto up the stairs = divide
deka
Unit
deci
centi
down the
stairs= multiply
milli
micro
For every step upward on the chart you are dividing by 10, or moving the decimal one place to the left. The exception is the top and bottom measurements: they jump three spaces.
Example: to convert 3025 milligrams to grams you are moving upward on the stairs. Pretend you are standing on the milligram stair step and to get to the gram stair you move up 3 steps dividing by 10 each time. 3025/1000 is 3.025g. Or you can use the shortcut and just move the decimal place one place to the left with each step up.
For every step downward on the chart you are multiplying by 10, or moving the decimal one place to the right. Again, the exception is the top and bottom steps, they jump three spaces.
Example: to convert 2 km to m you move 3 steps down on the chart so you multiply by 10 three times. You can do this easily by adding 3 zeros to the 2km. The answer is 2000 m.
Example with the top and bottom steps: You have 45 ML of liquid. How many cL is that? You are moving down the steps, so you multiply. Standing on the top step you start down by counting 3 for the first step. There are a total of 8 steps to the centi step. You multiply by 10, eight times, or add 8 zeros to the 45. Your answer is 4,500,000,000 cL.
Practice
1) 3 m = _______________cm
2) 40 liters = ____________daL
3) 600 mg = ______________g
4) 5 km = ________________hm
5) 70 mg = _________________cg
6) 54 cL = __________________mL
7) 6.7 Mm = _________________mm
8) Talal’s pet python measured 600 cm long. How many meters long was the snake?
9)
10) Hamad drank 4 liters of tea today. How many deciliters did he drink?
100 373K Absolute zero 273K 180° 100° 0°C 100°C 32°F 212°F
Celsius scale Fahrenheit scale Kelvin scale
water freezes at 0° water freezes at 32° water freezes at 273
water boils at 100° water boils at 212° water boils at 373
Ratio of Fahrenheit to Celsius is 180/100, or 9/5. If you are given a Celsius temperature and need to find the Fahrenheit you must take the 9/5 as well as the 32 degree difference in the scales. Use the following formula for the conversion:
Celsius to Fahrenheit (you are given °C and must find °F)
°F = 9/5 °C + 32° (be sure to multiply first)
Ratio of Celsius to Fahrenheit is 100/180, or 5/9. If you are given a Fahrenheit temperature and need to find the Celsius you must take the 5/9 as well as the 32 degree difference in the scales. Use the following formula for the conversion
Conversion for Fahrenheit to Celsius (you are given °F and must find °C)
°C = 5/9 (°F - 32°) be sure to subtract first
Conversions with the Kelvin scale are easy if you convert to Celsius. The scale “spaces” are the same size so it is a straight conversion. Use the following formula:
K = 273 + °C or °C = K – 293
If you need Fahrenheit from Kelvin, just convert first to Celsius and then to Fahrenheit.
Practice problems. Fill in the following chart with the correct temperatures. Round to the nearest whole number. Remember that you do not use the degree designation with the Kelvin temperature scale. Show your work at the bottom of the page.
|
°F |
°C |
K |
|
50° |
|
|
|
|
39° |
|
|
|
|
300 |
|
|
-28° |
|
|
-40° |
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