Name: ___________________________________________________________
Chapter 3
Period _________
Keller/Rosenzweig
Measurement & Reading Laboratory Equipment
Common Quantitative Measurements
Quantity
Volume
Definition
Metric Units
Mass
Temperature
balance
The average kinetic energy of particles in a
sample
thermometer
Length
Time
Equipment
Beaker,
graduated
cylinder
Meter stick or
metric ruler
how long something takes
Seconds (sec)
Energy
stopwatch
calorimeter
Celsius and Kelvin Temperature
The formula for converting from Celsius to Kelvin is: __________________________________________
The formula for converting from Kelvin to Celsius is: __________________________________________
Make the following conversions: (you can use your calculator).
25C = ____________K
345K = ______________C
1
READING LAB EQUIPMENT
RULE: Always read lab equipment one place value past the decimal value that you see!
EXAMPLE 1:
Ruler A: you can read to the tenths, so you estimate the hundredths
Length of nail when measured with Ruler A: _________________________________
Ruler B: you can read to the ____________, so you estimate to the ______________
Length of nail when measured with Ruler B: _________________________________
EXAMPLE 2:
Ruler A:
40 cm
Ruler B:
50 cm
40 cm
41 cm
Ruler A: you can read to the ____________, so you estimate to the ______________
Length of the line when measured with Ruler A: _________________________________
Ruler B: you can read to the ____________, so you estimate to the ______________
Length of the line when measured with Ruler B: _________________________________
2
3
SIGNIFICANT DIGITS: Determining Accuracy of Lab Equipment by Evaluating Measurements
All digits that are read or estimated in lab are considered “significant digits”. Any measurement given in a
lab report communicates three things to the reader: the numeric value of the measurement, the degree of
calibration of the equipment and the unit the measurement was taken in.
Here are some examples of determining significant digits from lab measurements:
Measurement
Equipment Read To:
Equipment Calibrated to:
14.0g
25mL
0.035mL
tenths place
ones place
thousandths place
ones place
tens place
hundreths place
# of significant
digits
3
2
2**
** notice that “place holder” zeros are not actually measured, so are not considered significant digits!
Follow the examples above to complete the chart below:
Measurement
Equipment Read To:
Equipment Calibrated
to:
# of significant
digits
233 °C
17.666 g
12.1 mL
0.00346 cm
920.5 kg
0.0250 L
127.0 g
13.555cg
952.0m
4
Zeros at the end of numbers without a decimal are difficult to interpret. For example – in the measurement
850mL, it is unclear whether the graduated cylinder was marked off to the hundreds and the fifty was estimated,
or whether it was marked off to the tens, and just happened to be on the line. Because of this, a decimal can be
placed at the end of the number to indicate that the zero was actually measured. Another way to indicate which
zeros were actually read is to draw a line over the last significant zero.
Calibrated to hundreds
Read to tens: 850mL
Measurement
Equipment Read To:
Calibrated to tens
Read to ones: 850. mL or
850mL.
850mL
tens
Equipment Calibrated
to:
hundreds
# of significant
digits
2
850. mL
ones
tens
3
1,200mL
hundreds
thousands
2
1,200 mL
tens
hundreds
3
5
Try: Complete the chart below:
Measurement
Equipment Read To:
Equipment Calibrated
to:
# of significant
digits
125.66L
131 g
0.00 45m
98 °C
125.4 cm3
0.099 mL
164.2 J
0.00000091 km
4,524.0 cal
550. dg
2,240 mL
3,200 kJ
1,960,000 nm
250g
6