Headstart 2026

Question 1

Accuracy

Answer 1

A measurement value is considered to be accurate if it is judged to be close to the true value of the quantity being measured.

Accuracy is a qualitative term; a measurement value or measurement result may be described, for example, as being ‘less accurate’ or ‘more accurate’ when compared with a true value.

Question 2

Precision

Answer 2

A measure of the repeatability or reproducibility of scientific measurements and refers to how close two or more measurements are to each other.

A set of precise measurements will have values very close to the mean value of the measurements.

Precision gives no indication of how close the measurements are to the true value and is therefore a separate consideration to accuracy

Question 3

Repeatability

Answer 3

How closely two successive measurements of the same quantity match, when carried out under the same conditions of measurement (observer, procedure, instrument, location).

Question 4

Reproducibility

Answer 4

How closely two measurements of the same quantity match, when carried out under changed conditions of measurement (observer, procedure, instrument, location)

Question 5

Resolution

Answer 5

The smallest change in the quantity being measured that results in a perceptible change on the measuring instrument. For example, the resolution of a burette is 0.10 mL.

Question 6

Validity

Answer 6

A valid experiment investigates what it sets out and/or claims to investigate.

Both experimental design and the implementation should be considered when evaluating validity.

An experiment and its associated data may not be valid, for example, if the investigation is flawed and controlled variables have been allowed to change.

Data may not be valid, for example, if there is observer bias.

Question 7

Random Errors

Answer 7

Affect the precision of a measurement and may be present in all measurements.

Random errors are unpredictable variations in the measurement process and result in a spread of readings

Eg subjective human judgement

Question 8

Systematic Errors

Answer 8

Cause readings to differ from the true value in a systematic manner so that when a particular value is measured repeatedly, the error is the same.

Systematic errors result from limitations in the instrument itself or incorrect calibration, or inappropriate methods (including parallax).

Question 9

Rules for Significant Figures (in Chemistry)

Answer 9

All digits where a number is expressed in standard form. For other numbers, all digits between the first non-zero digit and the final digit including trailing zeros. Whole numbers without a decimal point have the same number of sig-figs as digits in the number.

Question 10

Outliers

Answer 10

Data points or observations that differ significantly from other data points or observations are sometimes called outliers.

Outliers in data must be further analysed and accounted for, rather than being automatically dismissed, as an ethical approach to dealing with data.

Repeating readings may be useful in further examining an outlier: for example, to determine whether the outlier is a personal mistake.

Question 11

Steps for stoichiometry problems

Answer 11

1. Calculate the number of moles of ‘known’ (or limiting reagent, where applicable)
2. Use the molar ratio to determine the number of moles of ‘unknown’
3. Answer the question with appropriate sig figs and units.

Question 12

How to calculate % (w/v)

Answer 12

Determine the mass in grams of the solute that would be present in 100 mL of the solution i.e., g/100mL

Question 13

How to use the ideal gas equation to calculate volume in L

Answer 13

V = nRT/P

Question 14

How to use the ideal gas equation to calculate pressure in kPa

Answer 14

P = nRT/V

Question 15

How to use the ideal gas equation to calculate moles

Answer 15

n = PV/RT

Question 16

How to use the ideal gas equation to calculate temperature in Kelvin

Answer 16

T = PV/nR

Question 17

Standard conditions

Answer 17

25 degrees celsius and 100kPa

Question 18

Units in the ideal gas equation (except R)

Answer 18

Pressure in kPa, Volume in L, Amount in moles, Temperature in Kelvin

Question 19

Evidence for oxidation

Answer 19

Loss of electrons; Increase in oxidation number; gain of oxygen (except F); loss of hydrogen (eg organic molecules)

Question 20

Evidence for reduction

Answer 20

Gain of electrons; decrease in oxidation number; loss of oxygen (except F); gain of hydrogen (eg organic molecules)

Question 21

What happens to the oxidant (oxidising agent) in a redox reaction

Answer 21

It is reduced

Question 22

What happens to the reductant (reducing agent) in a redox reaction?

Answer 22

It is oxidised

Question 23

What is the site of oxidation?

Answer 23

The anode

Question 24

What is the site of reduction?

Answer 24

The cathode

Question 25

What is always present at the cathode?

Answer 25

The oxidant

Question 26

What is always present at the anode?

Answer 26

The reductant

Question 27

Steps for balancing a half equation

Answer 27

1. Balance the Key Element (changes oxidation number) 2. Balance Oxygen using water 3. Balance Hydrogen using H+ 4. Balance charge using electrons 5. Add state symbols

Question 28

Equivalence Point

Answer 28

The point in a titration when the solutions have reacted in the exact mole ratio as shown by the reaction equation. Neither reactant is in excess

Question 29

End Point

Answer 29

The point in a titration where an observation (eg colour change of the indicator) signals the end of the titration itself. Good experimental design will ensure that the end point is near the equivalence point in terms of volume of titrant delivered.

Question 30

Total range of concordant titres

Answer 30

Up to 0.10 mL

Question 31

Which of these is a correctly shown titre value? 10.59 mL, 10.55 mL, 10.4 mL

Answer 31

10.55 mL (2 decimal places with the second being 0 or 5)

Question 32

What should you rinse a burette with?

Answer 32

The solution to be used in the burette (titrant). Rinsing with water would dilute the titrant.

Question 33

What should you rinse a pipette with?

Answer 33

The solution to be used in the volumetric pipette (analyte). Rinsing with water would reduce the amount of analyte delivered in the aliquot.

Question 34

What should you rinse a volumetric flask with?

Answer 34

Water. Rinsing with the solution being measured out would increase the amount of that solution in the volumetric flask by an unknown quantity.

Question 35

What should you rinse a conical flask with?

Answer 35

Water. Rinsing with the analyte would increase the amount of analyte present in the conical flask by an unknown quantity.

Question 36

Mistakes

Answer 36

Sometimes called personal errors. Mistakes should not be included in reporting and analysis as part of the ethical consideration of data handling. Rather, the experiment should be repeated correctly.

Question 37

Uncertainty

Answer 37

The uncertainty of the result of a measurement reflects the lack of exact knowledge of the value of the quantity being measured. VCE Chemistry requires only a qualitative treatment of uncertainty.