Measuring and uncertainty

• Resolution: the smallest change an instrument shows. A burette reads to 0.05 cm³; a measuring cylinder to 1 cm³ or worse.
• Read volumes at eye level from the bottom of the meniscus.
• Repeat, spot anomalies, leave them out, take a mean.

uncertainty ≈ ± half the range of the repeats

• Random errors scatter readings; repeats and means reduce them.
• Systematic errors shift every reading the same way, such as a balance that is not zeroed (a zero error).
• Precise: repeats close together. Accurate: close to the true value. Repeatable: same person, same method agrees. Reproducible: others get the same.