Practical work - Facts

A testable statement

The variable that is changed

The variable that is measured

Variables that are kept constant to ensure valid results

The same person can repeat it and get the same results.

Different people can follow the method and get the same results.

Only the independent variable has been changed, the results are true

No graduations

if need to heat slowly or if the chemical is flammable

Spatula.

Balance

Burettes can measure variable volumes and add volume one drop at a time

Gas syringe / inverted measuring cylidner filled with water Filling with water can affect results if the gas is water soluble (systematic error)

Thermometer

The smallest change in a measured variable that an instrument can detect.

The degree to which a measured value reflects the true value.

The consistency of repeated measurements.

Errors that occur due measuring above or below the true value Reduce by making repeat measuriments and ignoring anomalous reuslts to calculate mean

Errors that occur consistently in the same direction, often due to faulty equipment.

A zero error occurs when an instrument does not read zero because it has not been calibrated.

Parallax error occurs when measurements are read at an angle rather than directly in line with the scale.

Calculate the range of the results and divide by two to find the uncertainty.

Determine the smallest division on the scale and divide by two.

Subtract the smallest value from the largest value in a set of results.