IB MYP 4-5 Physics- Measuring volume- Study Notes - New Syllabus
IB MYP 4-5 Physics- Measuring volume – Study Notes
Key Concepts
- Measuring Volume
Measuring Volume
Volume
Volume is the amount of space an object occupies. It is a derived physical quantity and is calculated based on the object’s shape or measured using instruments like measuring cylinders or syringes.
- SI Unit: cubic metre (\( \text{m}^3 \))
- Common subunits: \( \text{cm}^3 \), \( \text{mm}^3 \), \( \text{L} \) (litres), \( \text{mL} \) (millilitres)
- \( 1\,\text{cm}^3 = 1\,\text{mL} \), \( 1000\,\text{cm}^3 = 1\,\text{L} \)
Instruments for Measuring Volume
Measuring Cylinder
- Transparent, graduated tube with volume markings
- Used to measure volume of liquids or irregular objects by displacement
- Accuracy: usually to the nearest \( 1\,\text{mL} \)
Volumetric Flask / Pipette / Burette
- Used in chemistry for very precise measurements
- Accuracy: varies from \( 0.05\,\text{mL} \) to \( 0.1\,\text{mL} \)
Syringe
- Used to draw and measure liquids; marked in mL
- Good for low-volume accurate measurement (1–20 mL range)
Measuring Volume of Regular Solids
Use geometrical formulas:
| Diagram | Shape | Volume Formula |
|---|---|---|
 | Cube | \( V = a^3 \) |
 | Cuboid | \( V = l \times b \times h \) |
 | Cylinder | \( V = \pi r^2 h \) |
 | Sphere | \( V = \dfrac{4}{3} \pi r^3 \) |
Measuring Volume of Irregular Solids
Use the water displacement method in a measuring cylinder:
- Note the initial volume of water: \( V_1 \)
- Submerge the object completely
- Note the final volume: \( V_2 \)
- Volume of object: \( V = V_2 – V_1 \)
Precautions and Accuracy Tips
- Read the meniscus at eye level to avoid parallax error.
- Always read from the bottom of the meniscus for liquids.
- Ensure no air bubbles are attached to submerged solids in displacement.
- Use an appropriately sized cylinder for better precision (don’t use a 1L cylinder to measure 20 mL).
Example:
Why should a measuring cylinder be placed on a flat surface and the meniscus read at eye level?
▶️ Answer/Explanation
Placing the cylinder on a flat surface ensures a stable and level measurement. Reading the meniscus at eye level avoids parallax error, which can lead to incorrect volume readings.
Also, the correct reading is always taken from the bottom of the curved meniscus for most liquids.
Final Answer: \( \boxed{\text{To avoid parallax error and ensure accuracy}} \)
Example:
Explain how to measure the volume of an irregular stone using a measuring cylinder filled with water.
▶️ Answer/Explanation
1. Fill the measuring cylinder with a known volume of water — say \( V_1 \).
2. Gently lower the irregular stone into the water so it is fully submerged.
3. Record the new water level as \( V_2 \).
4. The volume of the stone is given by: \( V = V_2 – V_1 \)
Final Answer: \( \boxed{V = V_2 – V_1} \)
Example:
Initial water level in a measuring cylinder is \( 65\,\text{mL} \). After submerging a metal object, the level rises to \( 93\,\text{mL} \). Calculate the volume of the object.
▶️ Answer/Explanation
Use the formula: \( V = V_2 – V_1 \)
\( V = 93\,\text{mL} – 65\,\text{mL} = 28\,\text{mL} \)
Since \( 1\,\text{mL} = 1\,\text{cm}^3 \), the volume is also \( 28\,\text{cm}^3 \)
Final Answer: \( \boxed{28\,\text{cm}^3} \)