17.3: Metric System Conversions

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Lab Objectives

At the conclusion of the lab, the student should be able to:

describe the advantages of the metric system
convert units from base units of length, mass and volume
make predictions about the best units to use for various examples (for example, to measure a cell’s length would the student use meters or micrometers?)
record the measurement (either length, weight, or volume) of an item

Things you should be able to explain to someone else after this lab:

Celcius
Volume
Mass
Meter
Gram
Length
Area
Temperature
Liter

Slideshow

Thumbnail for the embedded element "Metric System"

A SlideShare element has been excluded from this version of the text. You can view it online here: pb.libretexts.org/bio1lm/?p=132

Introduction

Measurements in science use metric units. The metric system was developed in France in 1791 so that scientists had a common unit for research comparisons. In 1960 the metric system became the basis for the International System of Units (SI units). The basic units of these measurements for the metric system are listed in the chart below.

Unit	Metric Measure	Abbreviation
Length	Meter	m
Volume	Liter	L
Mass	Gram	g
Temperature	Celcius	ºC

Larger or smaller units are created by adding prefixes to the terms above. The metric system is based on units of 10, so conversions from one unit to another are relatively easy and can be completed by moving a decimal point either adding or subtracting zeros.

Prefix	Symbol	Multiplier	Notation
pico	p	0.000000000001	10⁻¹²
nano	n	0.000000001	10⁻⁹
micro	µ	0.000001	10⁻⁶
milli	m	0.001	10⁻³
centi	c	0.01	10⁻²
deci	d	0.1	10⁻¹
Base unit	g, m, or L	1	10⁰
deka	da	10	10¹
hecto	h	100	10²
kilo	k	1000	10³
mega	M	1000000	10⁶
giga	G	1000000000	10⁹
tera	T	1000000000000	10¹²

The chart on the previous page had some common metric prefixes from smallest to largest. Remember that the base unit, like a gram or a meter, is the same as 10⁰ or 1.

Now it’s time to practice!

Make the following metric conversions:

1 meter = __________ centimeters = __________ millimeters
56.2 millimeters = __________ meters = __________ centimeters
13 kilometers = __________ meters = __________ decimeters
16 ml = __________ µl 2. 7 g = __________ mg
9 µl = __________ L 4. 2.3 µl = __________ mL
32 mm = __________ nm 6. 19 m = __________ km
28 m = __________ km 8. 400 ml = __________ L
2 kg = __________ mg 10. 82 cm = __________ km

Part 1: Length and Area

Length is measured with a metric ruler, a meter stick, or a measuring tape. The basic unit of length is meters. Examine intervals marked on the metric rulers. You should see centimeter and millimeter divisions. Use a ruler to make the following measurements making sure to include units.

Length of the book __________.
Width of the book __________.
Area of the book __________.
(Area = length × width)
Diameter of a penny __________.
Measurement of object of your choice __________.

Lab Question

What are some potential sources of error in your measurements?

Part 2: Volume

Volume is the space occupied by an object. Units of volume are cubed (i.e. three dimensional) units of length. The liter (L) is the basic metric unit of volume.

Measure and pour 50 mL water into a 100 mL graduated cylinder. Notice how the water is curved. This is called the meniscus and is due to surface tension and adhesion of water molecules to the sides of the cylinder. When measuring liquids in a cylinder always get eye level with the meniscus and read the volume at the lowest level of the curve.
Fill a glass test tube with water. Use your graduated cylinders to measure the volume of the test tube in milliliters: __________.
Convert this volume to liters: __________.

Lab Question

What are some potential sources of error in your measurements?

Part 3: Micropipetting

Micropipettes are used to measure the volume of extremely small amounts of liquids. They are commonly used by researchers, hospital lab technicians, and by scientists in the food and drug industries. Micropipettes measure microliters (μl).

How many microliters are there in a milliliter?
How many milliliters are in a liter?
Therefore, there are __________ microliters are in a liter.

Micropipettors come in many sizes. For example, a p200 micropippettor can pipette up to 200 μl while a p1000 can pipette up to 1000 μl, or 1 ml, of liquid. Observe the micropettors available. Note that they are adjustable.

Practice micropipetting by following the instructions below. Your instructor will also demonstrate how to use the Pipetman.

Using a p20 Pipetman:

Set the micropipette for 15 μl by turning the dial.
Put a tip on the micropipette by firmly pressing the micropipette down into one of the tips and then twisting slightly. Usually the tips need to remain sterile, so tips are never to be picked up and put on the micropipette.
Hold the micropipette in the palm of your hand with your thumb on the white, round knob.
Push the knob down to the “first stop.” (You will notice that you can push down farther but it is much more difficult. This is the “second stop.”)
While holding the white knob down, put the tip of the micropipette into the sample and slowly release the knob. You will see the sample come up into the tip.
To dispense the sample, move the micropipette tip to a piece of parafilm and push the knob to the first stop and then to the second stop to expel the remaining liquid. Almost all of the sample should be released onto the parafilm. Note how small the 15 μl volume is!
You can now expel the tip into the waste by pressing the smaller white button. This is similar to the eject button on a hand-held mixer.

Lab Question

What are some potential sources of error in your measurements?

Part 4: Mass

The gram is the basic metric unit of mass. Use the electronic balance to measure the following items. Make sure that first you tare (set to zero) the balance. If you have a weigh boat, you must tare the balance with the weigh boat in place.

Rock __________
Penny __________
Paperclip __________
Convert your paperclip mass to mg __________

Lab Question

What are some potential sources of error in your measurements?

Part 5: Temperature

Scientists measure temperature in degrees Celsius (C). Here are some typical temperatures:

25ºC room temperature
37ºC human body temperature
75ºC hot coffee

Measure the following temperatures with the thermometers provided and feel with your fingers so that you have an idea of what that temperature feels like!

Room temperature __________
Hot bath __________
Inside refrigerator __________
Inside freezer __________

Lab Question

What are some potential sources of error in your measurements?

Contributors and Attributions

Biology 101 Labs . Authored by: Lynette Hauser . Provided by: Tidewater Community College. Located at: http://www.tcc.edu/. License: Public Domain: No Known Copyright. License Terms: As modified from Piedmont Virginia Community Collegeu2019s Biology 101 Biological Classification and the Metric System Lab