Introduction

In science, the metric system is used to express all units of measurement. Its primary advantage is the simplicity of converting from one unit to another, which can be done by moving the decimal point or multiplying and dividing by powers of ten. This makes calculations faster, more consistent, and less prone to error. In the laboratory, four fundamental quantities are commonly measured using the metric system: distance, volume, mass, and temperature.

In the metric system:
 the meter is the basic unit for distance,
 the liter is the basic unit for volume (also cubic centimeters),
 the gram is the basic unit for mass, and
 degrees Celcius are used as the basic unit for temperature.

Sources of error

In science, it is important to recognize potential sources of error in an experiment. Some errors are unavoidable, while others arise from human mistakes such as inaccurate measurements, poor observation, or careless technique. Common sources of error include the quality of the source materials, imprecision in equipment (unless a specific tolerance or scale unit is provided), improper equipment use (such as failing to zero a balance), and unaccounted-for environmental influences like temperature fluctuations. Errors can also stem from calculation mistakes, flawed logic, or weaknesses in the experimental design and statistical approach.

Measurement – length:

In the English system, length is commonly measured in inches, feet, and yards. In contrast, the metric system uses millimeters (mm), centimeters (cm), and meters (m). Very small structures—such as those observed under a microscope—are measured in micrometers (µm).

For this activity, obtain a meter stick. One side will display inches, while the opposite side shows metric units.

1. How many inches are in a meter? ____________________

2. How many centimeters are in a meter? ____________________

3. How many millimeters are in a meter? ____________________

4. How many millimeters are in a centimeter? ____________________

Next, obtain an irregularly shaped object from your instructor and measure its length.

5. What is the object? ____________________
   What is its length? ____________________

6. Describe your method of measurement and evaluate its accuracy.
   Consider whether your technique introduced any potential sources of error (for example, difficulty aligning the object with the meter stick, reading the scale at an angle, or uncertainty due to the object’s irregular shape). Explain how these factors may have affected your measurement.

Measurement – Volume:

Liquid volume is most commonly measured in liters (L) or milliliters (mL). The volume of a solid object can be determined by calculating length × width × height, and this value is typically expressed in cubic centimeters (cm³). Because 1 cm³ is equal to 1 mL, solid and liquid volumes can often be compared directly. In the laboratory, volume may be measured using a beaker, flask, or graduated cylinder. When reading the volume of a liquid, always observe the bottom of the meniscus—the curved surface formed as the liquid contacts the sides of the container—rather than the upper edge where droplets may cling.

7. Select one of the glassware items listed above and measure 15 mL of water.
   Which glassware did you choose? _______________________
   Why did you choose it? _______________________________

8. Is one type of glassware more accurate than another? Explain why:

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9. Obtain a test tube. What is the volume of the test tube? __________________

10. Describe your method for measuring the volume of the test tube:

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11. Obtain an irregularly shaped object. Describe how you would determine its volume:
    (Hint: consider water displacement.)

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12. What is the volume of the irregularly shaped object? ___________________

Measurement – Weight

In the metric system, mass is most often measured in grams (g) and milligrams (mg). These units allow for precise measurement of even very small objects, which is essential in laboratory work.

Obtain a paperclip and determine its mass using a balance.

13. How much does it weigh? _______ g = _________ mg

14. Convert 2 g to milligrams: 2 g = ________ mg

15. How much does 15 mL of water weigh? __________________

16. Describe the method you used to weigh the water:

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17. Describe any sources of error that may have affected your measurements:
    Consider factors such as zeroing the balance, evaporation, splashing, scale sensitivity, or the accuracy of your glassware.

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Measurement – Temperature:

In the metric system, temperature is expressed in degrees Celsius (°C). Understanding how to convert between Celsius and Fahrenheit is important, especially when comparing scientific data to everyday temperature references.

18. Convert 212°F to Celsius: __________________

19. Convert 100°C to Fahrenheit: __________________

Next, obtain a thermometer and measure the ambient temperature of the room.

20. What is the room temperature? __________________

21. Identify any potential sources of error in your temperature measurement:

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Licenses and Attribution

CC Licensed Content, Original:

Other Licensed Content Included:

• Adapted with permission from BioScience I Laboratory Manual by Jamie Colson-Moon and Denise Bristol. Per request from these original authors, this content is now licensed (CC BY-NC-SA).