Question

Select ALL of the following that are necessary to correctly measure the volume of a sample (single object or multiple objects) by displacement in water:

(Select all that apply.)

-For a group of objects all having the same composition (e.g. metal shot or powder), the volume of only one object at a time can be measured (e.g. a single speck of powder).
-The sample must not react with or dissolve in water.
-The sample's density must be greater than the density of water.
-The objects making up the sample must have a regular geometric shape (sphere, cylinder, etc.).

Answer 1

Answer with reasoning.

Of the four given statements, the correct ones are following

-For a group of objects all having the same composition (e.g. metal shot or powder), the volume of only one object at a time can be measured (e.g. a single speck of powder).

Explanation: Consider we have two objects A and B with an equal composition(mass) say M. Since, any water displacement method has to follow the Archimedes principle as well, hence we bring in the factor called density.

The density of any object of mass M and volume v is given by,

Say the density of A and B are da and db. If we immerse both objects simultaneously, Volume of water replaced will be M/da + M/db which will never give us individual volume for A and B. Now if we immerse A and B in water one at a time volume of water replaced by A= M/da and M/db by object B. We can easily find out these volumes by water displacement.

-The sample must not react with or dissolve in water.

If a sample reacts with water the chemical integrity of water will be lost leading to change in its initial volume as well as the sample which we are using will also lose its chemical and physical identity, like mass ( due to change in the chemical formula), density, state, and form, etc. Thus, the water displacement method will no longer be valid for such an experiment.

-The sample's density must be greater than the density of water

If the density of the sample is lower than water it will float on water and not be submerged.

If the density of the sample is equal to water it will be semi-submerged in water thus failing the experiment.

For a sample to displace water it should be fully submerged and for that, the density should be higher than water.

EXPLANATION:

The water displacement method is based on the Archimedes Principle, which states that a body submerged in a fluid at rest is pushed upward by a force with the magnitude of which is equal to the weight of the fluid displaced by the body.

The volume of displaced fluid = The volume of an object fully immersed in a fluid.

The weight of the displaced portion of the fluid is equivalent to the magnitude of the buoyant force, given by F

where d is density, V is the volume of fluid displaced and M is mass of the object.

***** Recommended https://www.middleschoolchemistry.com/lessonplans/chapter3/lesson2

and the Archimedes principle.

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F= M = d*V

A FLOATING BODY A BODY SINKS WHEN IT A BODY REMAINS IN EQUILIBRIUM weighs more than the fluid it displaces weighs loss than the fluid it displaces t weighs the same as the fluidit displace