Water Displacement

• how to measure the volume of an irregular solid using the water displacement method.
• how to combine displacement (for volume) with a balance (for mass) to calculate density.
• common sources of error in displacement experiments — absorption, trapped air, and parallax.

1. Water displacement method: submerge the object fully in water and measure the rise in water level; the rise in volume equals the object's own volume.
2. Eureka (overflow) can method: fill the can to the brim, submerge the object, and collect and measure the overflow — the overflow volume equals the object's volume.
3. To find density, measure both mass (using a balance) and volume (using displacement), then compute mass ÷ volume.
4. Floating objects can be measured by attaching a sinker: measure combined displacement, then subtract the sinker's own displacement.

A measuring cylinder has 40 mL of water. After lowering a metal bolt fully in, the level rises to 55 mL. Find the bolt's volume, and its density if its mass is 118.5 g.

Step 1 — find displaced volume: 55 − 40 = 15 mL = 15 cm³
Step 2 — recall density formula: density = mass ÷ volume
Step 3 — substitute: density = 118.5 ÷ 15 = 7.9 g/cm³
Step 4 — check: 7.9 g/cm³ is close to the known density of steel/iron, which is a sensible result for a metal bolt

• Not fully submerging the object, giving a smaller displaced volume than the true volume.
• Ignoring water absorbed into a porous object, which underestimates its true solid volume.
• Misreading the meniscus due to parallax, especially with tilted cylinders.

• Describe, step by step, how you would measure the volume of a small irregular stone.
• A rock displaces 35 cm³ of water and has a mass of 91 g. Find its density.
• How would you measure the volume of an object that floats?

Open the Practice tab for graded questions on Water Displacement.

• Use the platform-native live simulation or PhET-style tool for this topic (number line, Venn, physics playground, molecule builder, sensor dashboard, etc.).
• Mirror / body / home activity: physically do the concept (count objects, measure, role-play) and photograph or describe for portfolio.
• Voice or text reflection with AI Mentor: explain the concept to a younger student or family member.

• "Explain this concept to a Class 6 student using one real example from an Indian home, school, market, or festival."
• "What is one common mistake students make here, and how would you catch yourself making it?"
• Stretch: "How does this connect to coding, robotics, money, health, environment, or a future career?"

• Complete the core practice + one extension activity (photo, table, short reflection, or mini-project) for base XP + topic badge.
• 5-7 day streak or family discussion note = multiplier + visible artifact in parent/principal dashboard.
• Best real-world application stories (anonymised) featured on class or national leaderboard.

• One hands-on project or measurement using the Drishti kit or household items that makes the concept physical.
• Direct link to at least one Future Skill track (Money Management, Green Tech, Cyber Defenders, Micro-Entrepreneurship, AI Mastery, Sustainable Living, Personality Development).
• Coding extension where relevant (simple script, simulation, or data logging).

This material emphasises experiential "learning by doing", competency (apply/create/analyse), vocational exposure, critical thinking, and multidisciplinary connections. Designed to feed live worlds, AI Mentor (with memory), gamification, robotics, parent analytics, and future skills — not just exam prep.

Portfolio Evidence Idea: Your photo/table/reflection/project + one sentence on "How this helps me in real life or a possible future path."

Open the Practice tab for aligned questions (easy/medium/hard + case-based) with full AI scaffolding.

See curriculum for cross-links and the full future-skills/robotics chapters.