# What Does It Mean To Measure?

## Explore what can be measured and what it means to measure. Identify measurable properties such as weight, surface area, and volume, and discuss which metric units are more appropriate for measuring these properties. Refine your use of precision instruments, and learn about alternate methods such as displacement. Explore approximation techniques, and reason about how to make better approximations.

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### In This Session

Part A: Comparing Rocks
Part B: Which Rock Is the Largest?
Part C: Nonstandard Units
Part D: Summing It Up
Homework

In this session, you will begin to explore the questions “What can be measured?” and “What does it mean to measure something?” You will identify measurable properties of objects such as weight, surface area, and volume, and discuss which metric units are appropriate for measuring these properties. You will also learn that measurement is, by its nature, approximate. Finally, you will consider how to make measurements using nonstandard units.

For the list of materials that are required and/or optional in this session,
see Note 1.

### Learning Objectives

In this session, you will do the following:

• Begin exploring why measurement is always approximate
• Learn how to identify measurable properties as well as the metric units that are most appropriate for measuring these properties
• Use and learn about different methods for measuring, such as displacement
• Explore the advantages of using standard units when measuring

### Key Terms

New in This Session

Measurable Properties: Measurable properties can be quantified using a unit. When you combine objects possessing a measurable property, the property increases.

Measurement: Measurement is the process of quantifying properties of an object by comparing them with a standard unit.

Precision: The precision of a measuring device tells us how finely a particular measurement was made.

Surface Area: Surface area is the area enclosing a three-dimensional or solid object. You can find it by taking the sum of the areas of all of the surfaces of a three-dimensional object.

Unit: A unit is an appropriate and standard measurement that is used as the basis for other measurements. Examples of units are meters, seconds, liters, and grams.

Volume: Volume is the three-dimensional space taken up by an object.

Weight: Weight is the force of gravity on an object. An object in a gravitational field has both a mass and a weight, which are not the same thing. For example, an object in outer space might be weightless, but it still has mass.

### Notes

Materials Needed:

• A clean rock roughly the size of an egg
• Beakers marked with milliliters
• Tinfoil
• Fine sand or rice (optional)
• Two-pan balance and three-arm balance scale (optional)
• Calculator (optional)