When a question supplies a product label, the marks are for reading it accurately and staying inside what it says. Read the headings and units first, then calculate, then write a conclusion that matches the data.
This lesson is part of chemistry in health contexts. It pairs with distinguishing scientific evidence from marketing claims, which covers the wording side of the same skill.
How do you read a supplied label in three steps?
Do the steps in this order every time.
- Read every column heading and unit. Note what “per serving” or “per 100 g” refers to.
- Find the size of the pack or serving in the question, then scale the figure to match.
- Write what the figure shows, in one sentence, before you add any opinion.
The label is evidence. A sentence printed in large letters on the front is a claim, and the two are different things.
Worked example: a snack label with two columns
An invented snack bar label reads as follows.
| Nutrient | Per 100 g | Per bar (40 g) |
|---|---|---|
| Energy | 1 800 kJ | 720 kJ |
| Sugar | 30 g | 12 g |
| Salt | 0.5 g | 0.2 g |
The front of the pack says, “Only 12 g of sugar, a light snack.” A student eats 3 bars in a school day. Find the total sugar.
Step 1. The “per bar” column applies to one 40 g bar. Step 2. Total sugar = 3 × 12 g = 36 g.
The 12 g claim is true for one bar. Per 100 g the same bar is 30% sugar (12 ÷ 40 = 0.3), so the front of the pack shows a small number while the label shows the proportion.
The mistake that costs marks
The slip is to pick a figure from the wrong column. A student writes, “3 bars contain 3 × 30 g = 90 g of sugar”, using the per 100 g column for a 40 g bar.
| Step | Wrong | Right |
|---|---|---|
| Column used | per 100 g | per bar (40 g) |
| Working | 3 × 30 | 3 × 12 |
| Answer | 90 g | 36 g |
A quick check exposes it. Three bars weigh 120 g in total, so 90 g of sugar would be 75% of the bars, but the label shows only 30% sugar.
What should your conclusion sound like?
A good conclusion names the figure and stops. For the example above: “Each bar contains 12 g of sugar, and 3 bars contain 36 g. The label does not state a recommended limit, so the data cannot show whether this is too much.”
That last sentence is the scientific part. It says what the data cannot decide. Advice on what a person should eat belongs to a dietitian or doctor.
Check yourself
An invented juice label shows 8 g of sugar per 100 ml and a bottle size of 250 ml. The front says, “Natural sweetness.” Calculate the sugar in one bottle, then write one sentence about the claim.
Answer
250 ÷ 100 = 2.5, and 2.5 × 8 g = 20 g of sugar per bottle.
“Natural sweetness” describes the source, not the amount. The label shows 20 g of sugar, and the claim gives no figure to compare it with.
What to study next
Next, see where a neat example stops being reliable in recognising the limits of a classroom example. Then test yourself with the chemistry in health contexts practice set. The graph and evidence comparison lab helps when the supplied information is a chart.
If you want a teacher to go through label and data questions with you, see online one-to-one Science tuition.