CHEM1305.300
Lab 2: Significant Figures Lab Exercise
Significant Figures
We obtain measurements from equipment that is graduated (marked off into units). But do we bring our
measurement to the one’s place? The tenth’s place? The hundredth’s? It depends upon the markings on
your instrument. If your instrument is marked off to the tenth’s place, you can measure to the tenth’s
place with certainty. Your measurement, however, needs to go to the hundredths. You need to include
one estimated digit, which means you’ll have to divide the empty space in between lines into tens and
estimate where to end your measurement.
Look at the pencil to the left. We know for certain its length is at least 4.7 cm. But it extends a little
farther to where there is no marking. This is where you would add your one estimated digit. The length
should be either 4.72 cm or 4.73. If the pencil fell exactly over the 4.7 mark, you would still have to bring
your measurement to the hundredth’s place, so it would need to be recorded as 4.70 cm.
This ruler is divided into tenths, so your measurement needs to be reported to the hundredths.
, Now let’s look at a graduated cylinder, which is used to measure volume. The smallest markings are
divided into ones, so bring the measurement to the tenth’s space.
When you read a graduated cylinder, the liquid usually shows a strong attraction to the glass walls and
tends to creep up the sides, forming what we call a meniscus. Always get eye level with the bottom of
the meniscus when reading a graduated cylinder.
Looking at the close-up view, the volume is definitely past the 42 milliliter mark. The bottom of the
meniscus creeps up about three quarters of the way between 42 and 43, so report this volume as 42.7 or
42.8 ml.
Below is a picture of a triple-beam balance. Can you read the mass to the correct number of digits?
Your measurement should be 37.30 grams. If you left off the last 0, you’d be wrong. The scale’s smallest
graduation is to the tenth’s place, so bring your measurement to the hundredth’s place. Since the
pointer is directly on the 3, your estimated digit is a zero.
Many times, measurements are placed into calculations. For example, to find area, you would have a
base measurement and a height measurement multiplied by each other. What if one of the
measurements went to the tenth’s place and the other was measured more accurately, to the
hundredth’s place? There are rules you have to follow when adding, subtracting, multiplying, and
dividing measurements, but we have to start by learning significant figures.
Here are the rules to determining significant figures.
1) 1-9 are always significant. The number ‘329’ has 3 significant figures.
2) Any ‘0’ between 1-9 will be significant. So if you have 3008, the two zeros in between 3 and 8 are
significant. This number has 4 significant figures.
Lab 2: Significant Figures Lab Exercise
Significant Figures
We obtain measurements from equipment that is graduated (marked off into units). But do we bring our
measurement to the one’s place? The tenth’s place? The hundredth’s? It depends upon the markings on
your instrument. If your instrument is marked off to the tenth’s place, you can measure to the tenth’s
place with certainty. Your measurement, however, needs to go to the hundredths. You need to include
one estimated digit, which means you’ll have to divide the empty space in between lines into tens and
estimate where to end your measurement.
Look at the pencil to the left. We know for certain its length is at least 4.7 cm. But it extends a little
farther to where there is no marking. This is where you would add your one estimated digit. The length
should be either 4.72 cm or 4.73. If the pencil fell exactly over the 4.7 mark, you would still have to bring
your measurement to the hundredth’s place, so it would need to be recorded as 4.70 cm.
This ruler is divided into tenths, so your measurement needs to be reported to the hundredths.
, Now let’s look at a graduated cylinder, which is used to measure volume. The smallest markings are
divided into ones, so bring the measurement to the tenth’s space.
When you read a graduated cylinder, the liquid usually shows a strong attraction to the glass walls and
tends to creep up the sides, forming what we call a meniscus. Always get eye level with the bottom of
the meniscus when reading a graduated cylinder.
Looking at the close-up view, the volume is definitely past the 42 milliliter mark. The bottom of the
meniscus creeps up about three quarters of the way between 42 and 43, so report this volume as 42.7 or
42.8 ml.
Below is a picture of a triple-beam balance. Can you read the mass to the correct number of digits?
Your measurement should be 37.30 grams. If you left off the last 0, you’d be wrong. The scale’s smallest
graduation is to the tenth’s place, so bring your measurement to the hundredth’s place. Since the
pointer is directly on the 3, your estimated digit is a zero.
Many times, measurements are placed into calculations. For example, to find area, you would have a
base measurement and a height measurement multiplied by each other. What if one of the
measurements went to the tenth’s place and the other was measured more accurately, to the
hundredth’s place? There are rules you have to follow when adding, subtracting, multiplying, and
dividing measurements, but we have to start by learning significant figures.
Here are the rules to determining significant figures.
1) 1-9 are always significant. The number ‘329’ has 3 significant figures.
2) Any ‘0’ between 1-9 will be significant. So if you have 3008, the two zeros in between 3 and 8 are
significant. This number has 4 significant figures.
