General Science Measurement

Questions and Answers

What should you NOT do when holding a thermometer to measure temperature?

Ensure the thermometer is clean

Keep the bulb away from contact with surfaces

Hold the thermometer at the top

Let the bulb touch the glass (correct)

What defines precision in measurement?

The consistency of two or more measurements (correct)

The ability to achieve high accuracy

The closeness of a measurement to its accepted value

The variation between different types of instruments

If a measurement of 8.2 kg is recorded when the true value is 10 kg, how is this measurement characterized?

Low Precision and Low Accuracy

High Accuracy and High Precision

High Accuracy but Low Precision

High Precision but Low Accuracy (correct)

In a scientific investigation, when comparing the measurements of two objects, which principle is primarily assessed?

Both accuracy and precision should be assessed Signup and view all the answers

Why must a laboratory thermometer not be placed in the mouth?

Laboratory thermometers are not designed for oral use Signup and view all the answers

Which is true about achieving accuracy in measurements?

It requires frequent recalibration of the instrument Signup and view all the answers

What can often be the relationship between accuracy and precision?

They are independent concepts Signup and view all the answers

What can a thermometer's bulb touching a solid object cause during measurement?

False low temperature reading Signup and view all the answers

In repeated measurements of water temperature, if results vary between 20°C and 25°C, how do we classify this set of data?

Low accuracy and low precision Signup and view all the answers

When measuring temperature using a thermometer, what condition is essential for obtaining accurate results?

The thermometer should be held in an upright position Signup and view all the answers

Study Notes

Measurement Basics

Measurement involves determining the magnitude of a quantity relative to a standard.
Two main methods: indigenous (local practices) and modern (scientific community standards).

Indigenous Methods of Measurement

Passed down through generations, commonly associated with specific cultures.
Key indigenous units of measurement in Ethiopia:

Length Measurements

Hand-span: Distance from the tip of the little finger to the tip of the thumb.
Digit: Width of an adult male fingertip.
Cubit: Distance from the elbow to the tip of the middle finger.
Foot: Distance from the back of the heel to the tip of the big toe.
Pace: Distance of one normal walking step; measured from heel to heel.
Arm Span (Fathom): Distance between the middle fingertips when arms are fully extended.

Conversion Between Units

Example conversion: 200 meters is equivalent to 0.2 kilometers (200m / 1000m).
Exercises to practice conversions involving kilometers to centimeters, grams to kilograms, and minutes to hours.

Measuring Physical Quantities

Uses specific instruments for measurement:
- Mass: Measured with balances; based on the principle of comparing mass against a known standard.
- Temperature: Measured with thermometers, not touching the bulb or placing it in the mouth.

Accuracy vs. Precision

Accuracy: Closeness of a measurement to its known value.
Example: A measurement of 8.2 kg is inaccurate if the known mass is 10 kg.
Precision: Closeness of multiple measurements to each other.
Example: Mass measurements of 3.2 kg, 3.1 kg, 3.25 kg, and 3.3 kg are precise but not accurate if the true value is 10 kg.
Precision can occur without accuracy and vice versa.

Practicing Measurement Skills

Measure temperature of water using a laboratory thermometer and record findings.
Safety reminder: Do not touch the bulb of a thermometer or place it in the mouth during measurements.

Description

This quiz covers the various methods of measurement as discussed in the Grade 8 General Science curriculum. It highlights both indigenous and modern approaches to understanding measurement. Test your knowledge on how to measure quantities accurately and the standards involved in the process.