Water’s Properties: Density, Floating & Surface Effects — Practice · Grade 6 Science

Chapter: Matter, Mixtures & Water Properties

What this practice covers

By the end of Water’s Properties: Density, Floating & Surface Effects you should be able to:

8 questions, written answer and multiple choice, each with a worked explanation.

Vocabulary used: buoyancy, surface tension, evidence, system boundary, uncertainty.

Problem 1

Which is less dense than the modeled water?
Answer and explanation

The 20 mL object: 12 ÷ 20 = 0.6 g/mL. The second is 2 g/mL; the equal masses do not imply equal floating behavior.

Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.

Problem 2

Why can reshaping affect floating without changing the metal?
Answer and explanation

It changes the object’s geometry and enclosed air, allowing different displacement and average density.

Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.

Problem 3

Did the freezing model lose mass?
Answer and explanation

No. Mass stays 90 g while volume and density change with arrangement.

Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.

Problem 4

Does surface support prove the needle is less dense than water?
Answer and explanation

No. A surface force can matter for a small object; density and buoyancy must be considered separately.

Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.

Problem 5

Develop a complete response: Calculate ice density and explain the hull’s displacement without claiming that every metal floats. Include relevant evidence and one method or model limit.
Answer and explanation

Ice density is 0.9 g/mL. The hull displaces 60 g of modeled water, consistent with buoyancy balancing its weight. A hollow hull can float because of its overall geometry and average density; a compact piece of the same material may behave differently. Neither result is a rule for every temperature or liquid.

Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.

Problem 6

Apply the unit independently: A learner says the largest object must sink first. What measurements would you ask for? Give a reason and a relevant qualification.
Answer and explanation

Ask for mass, volume or displacement, shape, enclosed air, and the liquid’s properties. Size alone does not determine average density or buoyancy.

Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.

Problem 7

Which statement correctly uses buoyancy in Water’s Properties: Density, Floating & Surface Effects?
  1. The heaviest or largest object must always sink.
  2. buoyancy: The upward force a fluid exerts on an immersed or partly immersed object.
  3. Ice floats because freezing removes its mass.
  4. One illustrative result establishes every real condition and needs no further evidence.
Answer and explanation

buoyancy: The upward force a fluid exerts on an immersed or partly immersed object.

The upward force a fluid exerts on an immersed or partly immersed object. Ice density is 0.9 g/mL. The hull displaces 60 g of modeled water, consistent with buoyancy balancing its weight. A hollow hull can float because of its overall geometry and average density; a compact piece of the same material may behave differently. Neither result is a rule for every temperature or liquid.

Problem 8

Which statement correctly uses surface tension in Water’s Properties: Density, Floating & Surface Effects?
  1. Ice floats because freezing removes its mass.
  2. The heaviest or largest object must always sink.
  3. surface tension: An effect of particle interactions at a liquid surface that can influence small surface objects.
  4. One illustrative result establishes every real condition and needs no further evidence.
Answer and explanation

surface tension: An effect of particle interactions at a liquid surface that can influence small surface objects.

An effect of particle interactions at a liquid surface that can influence small surface objects. Ice density is 0.9 g/mL. The hull displaces 60 g of modeled water, consistent with buoyancy balancing its weight. A hollow hull can float because of its overall geometry and average density; a compact piece of the same material may behave differently. Neither result is a rule for every temperature or liquid.

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