Volume measuring instruments: the cylinder and the overflow can

Reading the level

A measuring cylinder is made of glass or clear plastic, with a scale in cubic centimetres (cm³ or cc) or millilitres (mL). It measures liquids and solids that do not dissolve.

Stand it on a horizontal surface and keep your eye level with the meniscus, the curved top of the liquid (Fig. 1.12).

Water curves downward; its concave surface is read at the bottom edge. Mercury curves upward; its convex surface is read at the top edge.

For a solid, note the level, drop the solid in, and note the new level. The rise is its volume. If the solid is too big for the cylinder, use a displacement can.

A solid under water pushes aside exactly its own volume of water. Measure the water it pushes aside and you have measured the solid.

Key terms

Measuring cylinder

Volume of liquids and of solids that do not dissolve.

Meniscus

The top level of the liquid, where you read the scale.

Concave / convex

Water curves down (read bottom); mercury curves up (read top).

Displacement can

Volume of a solid too big for the measuring cylinder.

Short questions with model answers

1. Q1. Activity 1.6: water stands at 20 mL. After a stone is put in, it stands at 26 mL. Find the volume of the stone.

   • 26 mL − 20 mL = 6 mL
   • 6 mL = 6 cm³

   6 cm³.

2. Q2. Where do you read the level for water and for mercury?

   • Water: concave, so read the bottom edge.
   • Mercury: convex, so read the top edge.

   Water at the bottom of the curve; mercury at the top.

Common mistakes

• ✗ Reading the water level at the top edge of the curve.

  ✓ Water is concave: read the bottom edge. Only mercury is read at the top.

• ✗ Looking at the meniscus from above or below.

  ✓ Eye level with the meniscus, cylinder on a horizontal surface (MCQ 1.5).

• ✗ Lowering the body before the can has started to overflow.

  ✓ Fill until it overflows first; otherwise some displaced water stays in the can.

MCQs

1. 1. MCQ 1.5: when using a measuring cylinder, one precaution is to:

   1. (a) Check for zero error
   2. (b) Look at the meniscus from below the water surface
   3. (c) Take readings from several directions
   4. (d) Keep the eye in line with the bottom of the meniscus
   Show answer

   (d) Eye level with the bottom of the water's meniscus (p. 17).

2. 2. MCQ 1.7: a displacement can is used to measure:

   1. (a) Mass of a liquid
   2. (b) Volume of a solid
   3. (c) Mass of a solid
   4. (d) Volume of a liquid
   Show answer

   (b) The overflow equals the volume of the solid body (p. 18).

3. 3. The surface of mercury in a cylinder is read at:

   1. (a) The top edge, because it is convex
   2. (b) The bottom edge, because it is concave
   3. (c) The bottom edge, because it is convex
   4. (d) The middle of the glass wall
   Show answer

   (a) Mercury curves upward (p. 17).

4. 4. MCQ 1.6: the volume of water you drink in a day is estimated in:

   1. (a) Millilitres
   2. (b) Kilograms
   3. (c) Litres
   4. (d) Cubic metres
   Show answer

   (c) A day's water is a few litres; kilograms is mass, and the others are too small or too large.

5. 5. In Activity 1.6, the liquid must be one in which the solid:

   1. (a) Floats
   2. (b) Dissolves quickly
   3. (c) Changes colour
   4. (d) Does not dissolve
   Show answer

   (d) Step 1 of Activity 1.6 (p. 18).

Quick revision

• Cylinder level, eye level with the meniscus: water at the bottom, mercury at the top.
• Volume of a small solid = rise in the liquid level.
• Too big for the cylinder: measure the overflow from a displacement can.