Using the Metric Ruler

Recognizing the Difference Between Centimeters (cm) and Millimeters

(mm) on the Metric Ruler

Each arrow below is pointing to a centimeter. (Enlarged)

Each arrow below is pointing to a millimeter. (Enlarged)

1. Place an arrow above 2, 5, 10 and 13 centimeters.

Exercises: 2. Place arrows above each millimeter between 6 and 7 centimeters.

3. Place an arrow above 85 mm.

4. Place an arrow above 120 mm.

Significant Figures and Recording Data

Counted values generally are not rounded and are reported exactly as they are counted. There should be no uncertainty in counted values, unless the numbers are very large. For example, if you perform an experiment with 25 pieces of copper, you can be certain that there exactly 25 pieces, not 24 or 26.

Measured values, such as the temperature of an object, or the mass of a sample, then record all the values of which you are certain, plus one additional place that you estimate.

Determine the number of significant figures shown. Examples:

Solution: The line is between 1.5 and 1.6 cm. We estimate the line to be at 1.51 cm. This gives us 3 significant figures.

Remember: Measured values, such as the temperature of an object, or the mass of a sample, then record all the values of which you are certain, plus one additional place that you estimate.

33 mL 2 sig. fig

a) b)

c) d)

e) f)

g) h)

Odometer

225 mL 3 sig. fig.

82.2 mL approx. 3 sig. fig. 1.35 cm 3 sig. fig.

5.95 cm 3 sig. fig. 50 mL 2 sig. fig.

135 mL 3 sig. fig. 1525.25 3 sig. fig.

Record the length in cm and mm of each line as precise as possible. Note: The rulers are not to scale.

1.

2. 4 7 cm

2.47 cm X 10 = 24.7 mm

2.

6. 3 9 cm

6.39 cm X 10 = 63.9 mm

3.

10. 8 0 cm

10.80 cm X 10 = 108.0 mm

4.

1 . 2 1 cm

1.21 cm X 10 = 12.1 mm