3.15 To measure the volume of bodies consisting of solid matter

Natural sciences

Matter, measuring and reactions

Educator section

Memorandum

3. Volume of stone:

Scientific formula

• You cannot use a formula, because the stone does not have the same length or width in all places.

Water displacement

Take a first reading of the water in the measuring-cylinder. Then bind thread around the stone and lower it into the water-filled cylinder. Wait for all the air bubbles to escape and take the second reading. Subtract the first reading from the second to determine the volume of the stone.

Leaner section

Content

Activity: to measure the volume of bodies consisting of solid matter [lo 1.2]

The examples that follow will help you to understand how volumes of solid bodies are measured.

(We use objects that can be fitted into the measuring cylinder):

A cube is a solid that has six square plane faces. The angle between two adjacent angles is a right angle. V = ℓ3

A triangular prism is a five-sided (polygonal) solid with identical triangular end planes and three rectangular plane faces perpendicular to the end planes.

V = ½bhH

A rectangular prism is a six-sided (hexagonal) solid that has two identical rectangular end planes and four side planes perpendicular to the end planes.

V = ℓbh

A cube is a solid that has six square plane faces. The angle between two adjacent angles is a right angle.V = ℓ3 A triangular prism is a five-sided (polygonal) solid with identical triangular end planes and three rectangular plane faces perpendicular to the end planes.V = ½bhH A rectangular prism is a six-sided (hexagonal) solid that has two identical rectangular end planes and four side planes perpendicular to the end planes.V = ℓbh

There are two methods for measuring the volume of the above objects:

• Measuring volume by applying a scientific formula;
• Calculating volume by means of the technique of water displacement.

The water displacement technique operates as follows:

The measuring cylinder is filled with water to the halfway mark. This halfway mark is your first reading of the water level. Now carefully lower the object of which the volume must be measured into the measuring cylinder.

Tap the side of the measuring cylinder to ensure that all air bubbles escape.

1. Now use both these methods to determine the volumes of the given objects:

6 x ½ = (3)

2. Was there any difference between the results obtained by the different methods?

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(1)

How do you explain the difference, if any, that you observe?

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(2)

3. Explain how you would determine the volume of a stone such as the one illustrated below?

• When using a scientific formula:

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(2)

• When measuring by means of water displacement:

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(2)

Assessment

Learning Outcome 1: The learner will be able to act confidently on curiosity about natural phenomena, and to investigate relationships and solve problems in scientific, technological and environmental contexts.

Assessment Standard 1.2: We know this when the learner conducts investigations and collects data: organises and uses apparatus/equipment or sources to gain and record information.