Record each reading to the precision the apparatus allows: the smallest division plus one estimated digit, and the same number of decimal places throughout the table. Precision (how finely you read) is not the same as accuracy (how close you are to the true value).
This lesson opens measurement and chemical investigation. The next lesson, identifying variables, decides which readings matter.
What precision does each apparatus give?
| Apparatus | Smallest division | Record to | Example |
|---|---|---|---|
| Burette (50 mL) | 0.1 mL | 2 decimal places | 24.30 mL |
| Pipette (25 mL) | Fixed volume | Stated value | 25.0 mL |
| Measuring cylinder (50 mL) | 1 mL | 1 decimal place | 32.0 mL |
| Thermometer (0 to 110 °C) | 1 °C | 1 decimal place | 28.5 °C |
| Electronic balance | Shown on display | As displayed | 12.46 g |
For a scale with divisions, read to half of the smallest division. The last digit is your estimate, so a zero at the end is meaningful and must be written.
How do you read a burette correctly?
Read the bottom of the meniscus with your eye level with it. Numbers on a burette increase downwards, which is the opposite of a measuring cylinder.
Take the initial reading before you start, and the final reading after. The volume delivered is final minus initial.
Worked example: a titration table
Question. A student records these burette readings. Complete the table.
| Reading 1 | Reading 2 | |
|---|---|---|
| Final reading (mL) | 24.80 | 47.35 |
| Initial reading (mL) | 0.50 | 24.80 |
| Volume used (mL) | ? | ? |
Working. Reading 1: 24.80 − 0.50 = 24.30 mL. Reading 2: 47.35 − 24.80 = 22.55 mL.
Both answers have two decimal places, matching the burette. Writing 24.3 would be marked down, because it hides the estimated digit.
The slips to watch for
The most common slip is to record 24.3 when the reading is exactly 24.30. The second is to forget that burette numbers increase downwards and add instead of subtract.
A third slip is to use a measuring cylinder when the question asks for an exact volume, because its divisions are too wide. Note each of these in your mistake log so you can spot your own pattern.
Check yourself
A burette starts at 1.20 mL and ends at 26.85 mL. State the volume delivered and the number of decimal places to use. A second student reads a 50 mL measuring cylinder as 18 mL. What should the reading look like?
Answer
26.85 − 1.20 = 25.65 mL, written to two decimal places.
A measuring cylinder with 1 mL divisions is recorded to one decimal place, so 18 mL is written 18.0 mL.
What to study next
Continue with identifying variables in a chemical investigation. Then test your readings with the chapter practice set.
For a teacher to correct your recording habits live, see online one-to-one Chemistry tuition.