### 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

## 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 | 10^{0} |

deka | da | 10 | 10^{1} |

hecto | h | 100 | 10^{2} |

kilo | k | 1000 | 10^{3} |

mega | M | 1000000 | 10^{6} |

giga | G | 1000000000 | 10^{9} |

tera | T | 1000000000000 | 10^{12} |

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 10^{0} 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?