Uncertainty

The uncertainty of a measurement which requires two readings is…

double the uncertainty of each individual reading

When you make a measurement of the change in temperature using the thermometer pictured above, what will the uncertainty in your answer be?

+- 2 degrees celsius

When you make a measurement of mass using the balance pictured above, what will the uncertainty in your answer be?

The resolution of the balance is 0.001g.
The uncertainty of a single=

reading=±resolution/2=±0.0012=± 0.0005g.

Because we’re measuring the mass, we need two readings, so the uncertainty is doubled:

2×±0.0005=±0.001g

When you make a measurement of the change in volume using the measuring cylinder pictured above, what will the uncertainty in your answer be?

±0.5 ml

How do you calculate percentage uncertainty?

uncertainty of measurement/measurement *100

Each reading from a thermometer has an uncertainty of ±2°C

In an experiment, this thermometer is used to measure a temperature change of 16°C

Using the equation above, calculate the percentage uncertainty in the temperature change.

Give your answer to 2 significant figures

To record temperature change, two readings must be taken. This means the uncertainty of measurement is double the uncertainty in each reading.

Uncertainty of measurement=2×±2⁢°C=±4⁢°C
Measurement=16⁢ °C
% uncertainty=4/16×100=25 ⁢%

A temperature sensor is used to measure the change in the lab’s temperature while a reaction runs overnight.

The minimum and maximum readings are shown below.

Calculate the percentage uncertainty in the change in temperature.

uncertainty of each reading= ±0.005⁢°C

percentage reading = 0.24%

How can you reduce the percentage uncertainty in a measurement? (2)

Change the instrument you measure with to one with a smaller resolution.

Alter the experiment to increase the quantity of whatever you’re measuring.