How to Use Data in Chemistry Questions

Data-based questions are increasingly prominent on 0620. They give you a table, a graph or a passage of information and ask you to extract, interpret or apply the data. These questions deliberately test skills beyond recall: they check whether you can use your chemistry knowledge on unfamiliar information. The good news is that the skill set is trainable, and the question types repeat.

The three types of data question

Type 1: extract information

The simplest type. The data is in a table or graph, and the question asks you to read a specific value.

“From the table, state the melting point of sodium chloride.”

All you need to do is read the correct cell in the table and write the value with units. The marks lost here are from reading the wrong row, the wrong column, or omitting the unit.

Tip: Circle or underline the relevant row and column before writing your answer. This takes two seconds and prevents the most common error.

Type 2: identify a trend or pattern

The question gives you data on a series of substances and asks you to describe the trend.

“Describe the trend in boiling point of the Group VII elements.”

To earn full marks:

1. State the direction of the trend: “The boiling point increases down the group.”
2. Support with data: “from -188 degrees C for fluorine to 184 degrees C for iodine.”
3. If asked to explain, link the trend to the underlying chemistry.

The data-support mark is specifically for quoting numbers. A statement without numbers often earns 1 of 2 marks.

Type 3: apply data to an unfamiliar context

The most challenging type. The question gives you information about a substance or reaction you have not studied and asks you to apply your knowledge to interpret it.

“The table shows the properties of substance X. Deduce the type of bonding and structure of substance X.”

The marks come from linking the properties to the bonding type:

• High melting point + conducts when molten = ionic.
• Low melting point + does not conduct = simple molecular (covalent).
• Very high melting point + does not conduct (except graphite) = giant covalent.
• Good conductor + malleable = metallic.

The data is unfamiliar, but the chemistry is standard. The skill is recognising which pattern fits.

How to read data tables

Step 1: read the headings

Before looking at any numbers, read every column heading and note the units. A column headed “temperature / degrees C” is different from “temperature change / degrees C.”

Step 2: scan for patterns

Look down each column. Is the data increasing, decreasing, or mixed? Are there anomalies (values that do not fit the trend)?

Step 3: connect to chemistry

Ask yourself: what topic does this table relate to? Melting points of elements across a period = bonding and structure. Volumes of gas collected over time = rates of reaction. Colours of precipitates = qualitative analysis.

Step 4: quote specific data in your answer

When the question asks you to “use the data” or “support your answer with evidence”, the mark scheme awards marks for specific numbers, not vague references.

Weak answer: “The element with more shells has a lower ionisation energy.” Strong answer: “Sodium (3 electron shells, ionisation energy 496 kJ/mol) has a lower ionisation energy than lithium (2 electron shells, ionisation energy 520 kJ/mol), because the outer electron is further from the nucleus.”

Dealing with unfamiliar substances

The exam sometimes includes substances not on the syllabus. This is deliberate. You are not expected to have memorised properties of every substance; you are expected to apply general principles.

The approach:

1. Read the properties given (melting point, conductivity, solubility, state at room temperature).
2. Match the properties to a known structure type (ionic, simple molecular, giant covalent, metallic).
3. State the structure type and explain how each property supports your conclusion.

Example: Substance Y has a melting point of 1610 degrees C, does not conduct electricity, and is insoluble in water.

Deduction: Giant covalent structure (1). High melting point because many strong covalent bonds must be broken (1). Does not conduct because there are no free electrons or ions (1).

Using data in calculations

Some data questions provide numerical data for a calculation. The key is to extract the correct numbers and apply the right formula.

Common traps:

• The table gives masses in kg but the calculation needs grams. Convert first.
• The table gives volume in cm3 but the formula needs dm3.
• The data includes a control experiment; do not use the control data for the calculation.

Always write what each number represents: “mass of CaCO3 used = 5.0 g (from the table).” This earns method marks and shows the examiner which data you selected.

Worked exam question

Q (Paper 4): The table shows the properties of four substances, A, B, C and D.

Substance	Melting point (degrees C)	Conducts as solid?	Conducts when molten?	Soluble in water?
A	801	No	Yes	Yes
B	-78	No	No	Slightly
C	1535	Yes	Yes	No
D	1713	No	No	No

(a) Which substance has a giant ionic structure? Explain your answer using data from the table. (3)

Model answer: Substance A (1). It has a high melting point of 801 degrees C, which indicates strong forces between ions in a giant lattice (1). It does not conduct as a solid (ions fixed) but conducts when molten (ions free to move), which is characteristic of an ionic compound (1).

The three marks: identification (1), melting point evidence with data (1), conductivity evidence with explanation (1). An answer without the specific data (801 degrees C) may lose the evidence mark.

Data questions reward careful reading and precise referencing. If data handling is costing marks, the issue is usually about answer discipline (quoting numbers, matching properties to structure types) rather than missing content knowledge. A trial lesson can practise data interpretation on real past-paper tables.