9.9 - Assignment Skills

What the National 5 assignment is

• Alongside the question paper, National 5 Chemistry has an assignment: coursework worth 20% of the total course award.
• It assesses skills the written paper can't: collecting your own experimental data, comparing it with published data, and referencing your sources.

The two stages

1. Research - Choose an aim, research the underlying chemistry, carry out an experiment to gather raw data, and find comparison data from the internet, books, journals, or the data booklet.
2. Report - Written up under supervision within a set time, producing a structured report with a table, graph, analysis, conclusion, and evaluation.

Allowed resources

During the report stage, you may use the data booklet, alongside your experimental data, research notes, and extracts from sources.

Choosing an aim and the underlying chemistry

• The assignment starts with a title and an aim, written separately.
• A good aim names both the variable you're changing (independent variable) and the one you're measuring (dependent variable) - e.g. "to find out how changing X affects Y".

Examples of aims

• Accepted - "To determine the effect of different de-icers on depressing the freezing point of water"; "To find out how increasing the temperature affects the rate of the reaction between oxalic acid and potassium permanganate".
• Rejected - "Investigate de-icers", "Investigate rates" - neither states what's being changed or measured.
• A phrasing such as "to investigate the burning of fuels and how much energy is released" is accepted because it clearly names what's measured.

The underlying chemistry

This section explains the chemistry behind your investigation and must show good understanding:

• Use your own words. Diagrams and chemical structures may be copied, but explanations must be written in your own words.
• Keep strictly to chemistry. Background history or economic uses earn no marks.
• Ensure accuracy. Every formula and balanced equation must match the exact substances in your aim (e.g. using ethanol rather than ethane).

Collecting and handling data

Carrying out the experiment

• Control variables - Keep all other variables constant so any change is due solely to the independent variable.
• Repeats - Repeat measurements to calculate an average (mean), which improves reliability.
• Range - Collect enough raw data across a suitable range for your aim (e.g. at least three different brands when comparing vinegars).

Finding comparison data

• You must find secondary data from a reliable source (internet, book, journal, or the data booklet) to compare with your experimental results.
• The comparison data must measure the same quantity or trend as your experiment. For example, comparing reaction times with published enthalpy values is invalid because they measure different quantities.
• Record the full reference for your source at the time you find it.

Processing data

• Calculated values (such as means or reaction rates) belong in your results table with their own column headings and units.
• You must always include your raw, unprocessed data alongside any calculated values.

Presenting your data

The table

• Include all raw data with clear headings and correct units for every column.
• Include any derived values or means in separate, fully labelled columns.
• Ensure column headings name the correct quantity and substance (e.g. "Mass of CO₂ lost / g", not "CaCO₃ lost").
• Check that all calculations and roundings are mathematically correct.

The graph

• Scatter graph or line graph - Used for continuous data (e.g. temperature, concentration). Plot points accurately and draw a line or curve of best fit if a trend is clear.
• Bar graph - Used for categoric data (e.g. different metals, particle sizes).

For all graphs:

• Use a linear, consistent scale that fills more than half the grid.
• Label both axes with the quantity and units, matching the table headings.

Analysing data and drawing a conclusion

The analysis

• State the relationship shown in your experimental results and compare it directly with your second source, identifying similarities and differences.
• State the relationship clearly (e.g. "as the concentration increased, the reaction rate increased").
• Avoid simply restating the data values or listing the variables without comparing the trends.
• Ensure your statements are fully supported by both sets of data and don't contradict your source.

The conclusion

• The conclusion must directly answer the aim, based on your own experimental results.
• It must refer to the exact quantities investigated in the aim.
• It must be chemically valid and supported by all the data presented in the report.

Evaluating the investigation

Identify a specific factor that affected the reliability, accuracy, or precision of your investigation, and explain what was done (or could be done) to minimise its effect.

Key definitions

• Reliability - Whether repeated measurements yield consistent results.
• Accuracy - How close your experimental values are to the true values (often shown by comparing against published literature).
• Precision - How finely a measurement can be made (determined by the apparatus used).

Genuine evaluation vs standard practice

Standard experimental techniques are not credited as evaluation points because they are expected as standard:

• Not accepted: "I used a stopwatch to time the reaction", "I measured the acid carefully", or "I avoided air bubbles".
• Accepted: Identifying a specific source of error and a concrete improvement - e.g. "Gas escaped while fitting the bung after adding the acid; using a divided flask would keep reactants separate until sealed, improving accuracy."

Writing up and referencing

Structure of the report

1. Title and aim
2. Underlying chemistry
3. Brief description of the experimental method
4. Raw data and processed data in a table
5. Comparison data from a second source
6. Graph
7. Analysis
8. Conclusion (answering the aim)
9. Evaluation

Referencing

Your comparison data must include a complete reference so a reader can find the original source:

Quoting directly from a source is permitted, but you must explain the information in your own words to demonstrate understanding.

Common exam questions

Question 1

Roughly how much of the National 5 course award is the assignment worth?

About 20% - a fifth of the grade - so it carries the credit for skills the written paper cannot test, such as collecting your own data and referencing sources.

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Question 2

What are the two stages of the assignment?

Research, in which you settle on an aim, carry out an experiment that gives you measurements, and gather comparison data from a source; and the report, written up under closer supervision.

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Question 3

Why is "investigate effectiveness of alcohols as fuels" not an acceptable aim, when "to investigate the burning of fuels and how much energy would be released" is?

The first names a topic but not a variable to change or a quantity to measure. The second, although plainly worded, states what is actually being measured: the energy released.

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Question 4

Besides your own experimental results, what other data must the report contain, and where can it now come from?

Comparison data from the internet, a book, a journal, or the data booklet, gathered so you can compare your own results against it, together with a reference for where it came from.

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Question 5

A candidate measured the time taken for a temperature rise, then compared that against a published table of enthalpy values. Why is this a weak comparison?

Time and enthalpy are different quantities. Comparison data has to be genuinely relevant to what you actually measured, not just on the same general topic.

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Question 6

A candidate's table gave the units for a rate as grams rather than grams per minute. What is missing?

A rate is a change per unit of time, so its unit must include the time as well as the quantity, such as grams per minute.

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Question 7

What does the analysis section have to do that the question paper never asks for?

State a relationship between your own experimental results and the data you found from your source, including any similarities and differences, rather than just describing your own results on their own.

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Question 8

The evaluation asks for a factor affecting the reliability, accuracy, or precision of your results. Why would "I used a stopwatch to time it" not earn the mark?

Because using a stopwatch for a timed reaction is standard practice, not a weakness specific to this investigation. A genuine factor is something that could actually have gone wrong in your own experiment.

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Question 9

Why must you reference the source you used for your comparison data?

Because any information or data that is not your own must be credited, in enough detail for a reader to find it again; referencing is a required part of the write-up.