Pressure, by itself, does not directly change mass. However, pressure can affect the density of a substance, and since density, mass, and volume are related, changes in density due to pressure can lead to changes in volume for a fixed mass.
Here's a breakdown:
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Mass is a fundamental property: Mass is a measure of the amount of matter in an object. It is an intrinsic property and remains constant unless matter is added or removed.
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Pressure and Density: Pressure is force per unit area. Increasing the pressure on a substance, particularly a gas, forces its particles closer together. This leads to an increase in density (mass per unit volume). The relationship is generally inversely proportional when mass is constant. The reference states "the density of a fluid is inversely proportional to its pressure hence, as pressure is increased, a decrease in density is observed, mass etc. being kept constant". However, that quoted statement is incorrect. Increasing pressure typically increases density.
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The Relationship: Density = Mass / Volume This equation is key. If the mass stays constant and the density changes (due to pressure), then the volume must also change to compensate.
Examples:
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Gas Compression: When you compress a gas (like in a bicycle pump), you increase the pressure. The mass of the gas remains the same, but the volume decreases, and the density increases.
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Liquids and Solids: Liquids and solids are much less compressible than gases. Therefore, pressure has a smaller effect on their density and volume. However, at extremely high pressures, even liquids and solids will experience a change in density and volume.
In Summary:
While pressure doesn't directly alter the mass of an object, it can change its density by affecting its volume. The mass itself remains constant unless there's an addition or removal of matter. It's crucial to remember the relationship: Density = Mass / Volume.
