Measurement

1. Units of Measurement

• Units are used in science to show measurements.
• Without units, numbers can be unclear. Units give meaning to numbers.
• The SI unit is the standard unit used worldwide in science.

Unit	Symbol	Measurement
Metre	m	Length
Kilogram	kg	Mass
Second	s	Time
Kelvin	K	Temperature
Mole	mol	Amount of Substance
Ampere	A	Electric Current
Candela	cd	Luminous Intensity

2. Length

Length measures the distance between two points.

Common tools: Ruler, Metre stick, Trundle wheel, Vernier callipers, Opisometer.

• Ruler and Metre stick: For straight lines.
• Trundle wheel: For long, curved lines.
• Opisometer: For short, curved lines on maps (often replaced by digital maps).
• Vernier callipers: For measuring the diameter of circular objects.

3. Mass

• Mass is the amount of matter in an object.
• Common units: grams (g), kilograms (kg).
• People often confuse mass with weight. Weight is a force (see the chapter on forces).
• Tool for measuring mass: Mass balance (not weighing scales).

4. Area

• Area is the surface an object covers.

• Common units: square metres (m²), square centimetres (cm²). Formulas:

  • Square/Rectangle: Length x Width
  • Circle: π x radius² (πr²)

5. Volume

• Volume is the space an object occupies.
• Common units: cubic metres (m³), cubic centimetres (cm³), millilitres (mL).
• Tools for measuring volume: Graduated cylinder, pipette, graduated droppers.
• Formula: Length x Width x Height

6. Calculating Area and Volume:

• Area of Rectangle: Length × Width
• Area of Triangle: ½ × Base × Height
• Volume of Cuboid: Length × Width × Height
• Volume of Cylinder: π × Radius² × Height

7. Measuring the Volume of an Irregular Solid

1. Fill an overflow can to the spout.
2. Lower the object gently into the can using a string to prevent splashing.
3. Ensure the object is completely submerged.
4. Collect the water that overflows into a graduated cylinder. This is the volume of the object.

8. The Meniscus

• Liquids in containers form a curve at the edges, known as the meniscus.
• This is more noticeable in narrow containers.
• Always read the measurement at eye level, from the bottom of the meniscus.

9. Error of Parallax

• Parallax error occurs when you read a measurement from an angle, causing an inaccurate reading.
• To avoid this, always read the measurement directly in front of the scale.

10. Measuring Instruments:

• Ruler/Measuring Tape: Used for measuring length.
• Balance Scale: Used for measuring mass.
• Graduated Cylinder: Used for measuring the volume of liquids.
• Stopwatch: Used for measuring time.
• Thermometer: Used for measuring temperature.

11. Accuracy and Precision:

12. Significant Figures:

• Significant figures indicate the precision of a measurement.
• Example: 23.5 has three significant figures.

13. Practical Applications

1. Measuring Length:

• Use a ruler or measuring tape for straight objects.

• Use a trundle wheel for longer distances. 2. Measuring Mass:

• Use a balance scale for small objects.

• Use a digital scale for more precise measurements. 3. Measuring Volume:

• Use a graduated cylinder for liquids.

• Use the water displacement method for irregularly shaped objects. 4. Measuring Time:

• Use a stopwatch for timing events.

• Use a clock for longer durations. 5. Measuring Temperature:

• Use a thermometer for liquids and gases.

• Use a digital thermometer for more accurate readings.

14. Important Points to Remember

• Always use the correct unit for the type of measurement.
• Ensure the measuring instrument is properly calibrated.
• Take multiple measurements to ensure accuracy and precision.
• Record measurements to the correct number of significant figures. Understanding measurement is crucial in science as it allows us to quantify and compare observations. By using standard units and precise instruments, we can ensure our measurements are accurate and reliable.

15. Mandatory Experiments