The x-axis runs across the bottom. The y-axis runs up the side. Start with values printed beside the axes.
Start at 20 s on the x-axis.
Draw a line up to the plotted line.
Draw a line across to the y-axis: 40 cm³.
At 20 s, the volume of gas is 40 cm³. Both readings are on numbered marks.
Read the numbered marks in reverse
The blue lines show the reading route.
At what time is the water at 40 °C?
Start at the temperature on the y-axis. Follow the blue guide across to the graph, then down to the time axis.
Start at 40 °C on the y-axis.
Go across to the plotted line.
Go down to the x-axis: 20 s.
The water is at 40 °C after 20 s. Both readings are on numbered marks.
Count the small intervals
Count the intervals shown in blue.
What does one small interval on the time axis represent?
Find the difference between two neighbouring numbered marks. Divide by the number of equal small intervals between them. Count the intervals.
Find the numbered difference.
Count the equal intervals.
Divide to find one interval.
From 0 s to 20 s there are 4 small intervals. Each interval is 20 ÷ 4 = 5 s.
Read y from a given x
The blue lines show the reading route.
What is the temperature at 4 min?
Start at the given x-value. Go up to the plotted point or line, then across to the y-axis. Read the value and its unit.
Find x on the horizontal axis.
Go up to the graph.
Go across to read y.
At 4 min, go up to the marked point, then across. The temperature is 45 °C.
Read x from a given y
The blue lines show the reading route.
At what time is the water at 35 °C?
Start at the given y-value. Go across to the plotted point or line, then down to the x-axis. Read the value and its unit.
Find y on the vertical axis.
Go across to the graph.
Go down to read x.
At 35 °C, go across to the marked point, then down. The time is 6 min.
Read between plotted points
The blue lines show the reading route.
What distance does the graph show at 5 s?
When a value lies between measured points, follow the line joining them. A reading between the points is an estimate from the graph.
Find the given x-value.
Go up to the straight line, then across.
Read the y-value using its scale.
5 s is halfway between 4 s and 6 s. On this straight line the distance is halfway between 20 m and 30 m: 25 m. There is no extra measured cross at 5 s.
Read decimal scales
The blue lines show the reading route.
What current does the graph show at 1.5 V?
Use the same interval method when the numbered values are decimals. Count on carefully in the size of one small interval.
Find the value of one small interval.
Count on using that decimal amount.
Between 0.2 A and 0.4 A are 4 small intervals, so each is 0.05 A. At 1.5 V, the marked point shows 0.30 A.
Compare two plotted values
The blue lines show the reading route.
How much higher is the temperature at 6 min than at 2 min?
Read both values from the same axis. To find how much higher one is, subtract the smaller reading from the larger reading. Keep the unit of those readings.
Read both y-values.
Subtract to find the difference.
Include the y-axis unit.
At 2 min the temperature is 25 °C. At 6 min it is 55 °C. The difference is 55 − 25 = 30 °C.
Your turn
Question 1 of 18 · 0 completed
1. Gas collected over time
Straight lines join the marked points.
What volume of gas is collected at 10 s?
Start at 10 s. Go up to the graph, then across to the volume axis.
The guide goes up from 10 s and across to the numbered mark at 20 cm³.
2. Cooling water
Straight lines join the marked points.
At what time is the water at 60 °C?
Start at 60 °C. Go across to the graph, then down to the time axis.
The guide goes across from 60 °C and down to the numbered mark at 10 s.
3. Water temperature over time
Straight lines join the marked points.
Which quantity is shown on the horizontal x-axis?
Read the label below the horizontal axis.
The horizontal axis is labelled Time (min), so its quantity is time. The unit is minutes.
4. Spring length with added mass
Straight lines join the marked points.
Which unit is used on the vertical y-axis?
Look at the unit in brackets beside the vertical axis.
The vertical axis is labelled Length (cm). Its unit is centimetres, written cm.
5. Warming water
Straight lines join the marked points.
What does one small interval on the temperature axis represent?
Count the intervals between 20 °C and 40 °C, then share the 20 °C difference equally.
There are 4 equal small intervals between 20 °C and 40 °C. Each is (40 − 20) ÷ 4 = 5 °C. Count intervals, not the 5 tick marks that bound them.
6. Gas collected over time
Straight lines join the marked points.
What time is shown one small interval to the right of 15 s?
There are 3 equal small intervals from 15 s to 30 s.
Each small interval is (30 − 15) ÷ 3 = 5 s. One interval to the right of 15 s is 15 + 5 = 20 s.
7. Heating water
Straight lines join the marked points.
What is the water temperature at 4 min? Read the marked point.
Go up from 4 min to the marked point, then across to the temperature axis.
The marked point at 4 min lines up with 45 °C. The y-axis small intervals are 5 °C.
8. Volume of gas collected
Straight lines join the marked points.
What volume of gas has been collected at 8 s? Read the marked point.
Go up from 8 s. Check how much each small interval on the volume axis represents.
The volume axis has 3 small intervals per 12 cm³, so each is 4 cm³. The point at 8 s shows 32 cm³.
9. Distance travelled by a robot
Straight lines join the marked points.
Straight lines join the marked points. What distance does the graph show at 5 s, between the points at 4 s and 6 s?
At 5 s, read the straight line halfway between the two marked points.
5 s is halfway between 4 s and 6 s. On their straight-line join, the distance is halfway between 20 m and 30 m: 25 m.
10. Water warming during an experiment
Straight lines join the marked points.
Straight lines join the marked points. What temperature does the graph show at 3 min, between the points at 2 min and 4 min?
Go up from 3 min to the straight line, then across.
3 min is halfway between 2 min and 4 min. The straight line is halfway between 30 °C and 50 °C there, so the temperature is 40 °C.
11. Cooling water
Straight lines join the marked points.
At what time is the water at 35 °C? Read the marked point.
Go across from 35 °C to the marked point, then down to the time axis.
The marked point at 35 °C lies above 6 min. Read across from y, then down to x.
12. Height of a seedling
Straight lines join the marked points.
At what time is the seedling 14 cm tall? Read the marked point.
Find 14 cm on the height axis, go across to the marked point, then down.
The marked point at 14 cm lines up with 8 days on the horizontal axis.
13. Gas volume during a reaction
Straight lines join the marked points.
Straight lines join the marked points. At what time does the graph show 20 cm³, between the points at 4 min and 6 min?
Go across from 20 cm³ to the straight line between the two points, then down.
20 cm³ is halfway between 16 cm³ and 24 cm³. On the straight-line join, it occurs halfway between 4 min and 6 min: 5 min.
14. Water cooling during an experiment
Straight lines join the marked points.
Straight lines join the marked points. At what time does the graph show 50 °C, between the points at 2 min and 4 min?
Go across from 50 °C to the falling straight line, then down.
50 °C is halfway between 60 °C and 40 °C. The straight line reaches it halfway between 2 min and 4 min, at 3 min.
15. Current through a component
Straight lines join the marked points.
What current does the graph show at 1.5 V? Read the marked point.
Each small interval on the current axis is 0.05 A. Go up from 1.5 V, then across.
The point at 1.5 V shows 0.30 A. It is two small intervals above 0.20 A: 0.20 + 0.05 + 0.05 = 0.30 A.
16. Extension with added mass
Straight lines join the marked points.
Straight lines join the marked points. What added mass does the graph show for an extension of 2.5 cm, between the points at 0.4 kg and 0.6 kg?
Go across from 2.5 cm to the straight line, then down. Check the decimal mass scale.
2.5 cm is halfway between 2 cm and 3 cm. On the straight-line join, the mass is halfway between 0.4 kg and 0.6 kg: 0.5 kg.
17. Temperature while heating water
Straight lines join the marked points.
How much higher is the water temperature at 6 min than at 2 min? Read the marked points.
Read both temperatures, then subtract the earlier reading from the later reading.
At 2 min the temperature is 25 °C, and at 6 min it is 55 °C. The increase is 55 − 25 = 30 °C.
18. Mass of a sample while drying
Straight lines join the marked points.
How much mass is lost between 2 h and 6 h? Read the marked points.
Read the mass at each time. Subtract the final mass from the starting mass.
The sample has a mass of 45 g at 2 h and 25 g at 6 h. The mass lost is 45 − 25 = 20 g.
All 18 questions completed
You have practised axes, intervals, graph readings and comparisons.