NCERT Solutions Curiosity Chapter 9 .5.1 Determination of density — Activity 9.4: Let us observe and calculate
Book page 1439 Updated on2026-09-05
Q1.
What is the maximum volume it can measure?
Answer
100 mL. The cylinder in Fig. 9.16 is marked 100 mL at the top of its scale, and that top mark is the largest volume it can measure in one filling.
Why it is fixed: The capacity is decided by the length of the graduated part of the tube. Filling past the last mark tells you nothing, because there are no divisions above it to read.
Tip: Always check this number before you start. Trying to measure 150 mL in a 100 mL cylinder means two fillings — and two chances to make a reading error.
Q2.
How much is the volume difference indicated between the two bigger marks (for example, between 10 mL and 20 mL)?
Answer
10 mL. On the cylinder in Fig. 9.16 the numbered marks run 10, 20, 30 … up to 100, so the step from one numbered mark to the next — 10 mL to 20 mL, or 40 mL to 50 mL — is 10 mL every time.
Why the marks are evenly spaced: The cylinder has the same width all the way up, so the same volume of water always raises the level by the same height. That is what makes a straight, evenly divided scale possible — and it is one more reason the vessel is made a cylinder and not a cone or a flask.
Q3.
How many smaller divisions are there between the two bigger marks?
Answer
10. Count the fine lines between 10 mL and 20 mL on Fig. 9.16 — there are ten equal spaces from one numbered mark to the next.
Tip: Count the spaces, not the lines. Between two numbered marks you will see nine short lines, which cut the gap into ten spaces. Counting lines instead of spaces is the commonest mistake in finding a least count.
Q4.
How much volume does one small division indicate?
Answer
1 mL. Ten millilitres are shared equally among ten divisions.
Volume between two bigger marks = 10 mL
Number of divisions between them = 10
One small division = 10 ÷ 10 = 1 mL
Why this works: This is exactly the method you used for the thermometer in Curiosity, Grade 6 — take the value of one full step of the numbered scale and divide it by the number of equal parts that step is cut into. It works for any linear scale: a ruler, a thermometer or a measuring cylinder.
Q5.
The smallest volume that the measuring cylinder can read is__________.
Answer
1 mL — for the 100 mL measuring cylinder shown in Fig. 9.16.
This smallest readable value is called the least count of the instrument. It sets the limit of what the cylinder can tell you: with a least count of 1 mL you can honestly report 47 mL, but not 47.3 mL.
Cylinder
Volume between big marks
Divisions
Smallest reading
100 mL (Fig. 9.16)
10 mL
10
1 mL
10 mL or 25 mL
1 mL
10
0.1 mL
250 mL
10 mL
5
2 mL
500 mL
50 mL
10
5 mL
Tip: If the cylinder in your school lab is a different size, do not copy 1 mL. Work out its own least count from its own scale.