Measuring liquid and solid volume
Read a measuring cylinder at the meniscus and find the volume of an irregular solid by displacement.
On this page
Food Chemistry · about 25–35 min
What you need to understand
Read the scale, subtract final minus initial and include mL or cm³.
Definitions
- volume
the amount of space occupied by a substance or object
For example: Water displacement can measure an irregular solid’s volume.
Explanation
Stand the measuring cylinder upright on a level surface. Read the scale at eye level with the bottom of the curved water surface, called the meniscus. First count the intervals between numbered marks to find the volume represented by each small division. Looking from above or below shifts the apparent reading.
To measure an irregular solid, record the starting water volume, lower the solid until fully submerged and record the new reading. The rise is the volume displaced: final reading minus initial reading. Use a solid that does not dissolve or absorb water, and remove trapped air bubbles. A partly submerged solid does not displace its full volume.
Pause and say it: Read the scale, subtract final minus initial and include mL or cm³.
Common mistake
Tempting wrong idea: A measuring cylinder measures mass.
Why it fails: The cylinder scale is marked in volume units such as mL. It has no balance or mass scale. Use a balance to measure mass in units such as grams.
Use this instead: A measuring cylinder measures volume; mass is measured with a balance.
Worked Example
Modelled example 1
Read the rise in water level
Problem
A solid is lowered fully into the water without spilling any. It does not dissolve or absorb water, and no air bubbles are trapped. Read these scale close-ups at eye level using the bottom of each water meniscus. What is the solid’s volume?
Study the worked solution
Read one division
Method
Count the equal intervals between 20 and 30 mL.Reason
The numbered difference covers five intervals, not five extra millilitres.Working
Each small division is (30 − 20) ÷ 5 = 2 mL. The starting reading is 24 mL and the final reading is 32 mL.Find the displaced volume
Method
Subtract the starting water volume.Reason
The final reading includes the water already in the cylinder. Only the rise is due to the solid.Working
Solid volume = 32 − 24 = 8 mL = 8 cm³.
Guided practice
Try it with support
A cylinder has five equal intervals from 20 mL to 30 mL. The bottom of the water meniscus is on the second small mark above 20 mL. Read the volume.
Count intervals, not the number of marks.
Check the guided answer
Answer: Each interval is 2 mL, so the reading is 24 mL.
Check: Read at eye level; do not read the higher edges of the meniscus.
Practise and continue
Practise this
Water rises from 18 mL to 29 mL when a non-absorbing solid is fully submerged. Find the solid volume.
Need a hint?
Find the increase in water level.
Check your answer
Answer: 29 − 18 = 11 mL, equivalent to 11 cm³.
Check: 29 mL includes the original water; grams would be a mass unit.
Think like a scientist
A learner reads the cylinder from above while part of the solid remains out of the water. State two repairs.
Check the reasoning
Read the bottom of the water meniscus at eye level and fully submerge the solid before taking the final reading.
Remember: Remove trapped bubbles and use a solid that does not dissolve or absorb water.
One-minute check
How do you find the volume represented by one small scale division?
Why do you read the bottom of a water meniscus at eye level and subtract the starting volume?
Correct this common mistake: “A measuring cylinder measures mass.”
Syllabus and review details
- SEC G1 Science 2027 · 2027
Content structure and syllabus content, PDF pages 8–17
Last reviewed: