Question

Which physical state is described as having a variable shape and compresses negligibly?

Short answer

The liquid state.

Step-by-step solution

Identify Physical States

There are three basic physical states: solid, liquid, and gas. Solids have a definite shape and volume, gases have neither a definite shape nor volume, and liquids have a definite volume but take the shape of their container.

Assess Compression Characteristics

Solids and liquids compress negligibly, meaning their volumes do not change significantly under pressure. Gases, on the other hand, are easily compressed.

Evaluate Shape Flexibility

Liquids have a variable shape because they take the shape of their container, unlike solids, which have a fixed shape. Gases also take the shape of their containers, but we focus here specifically on liquids due to compression characteristics.

Determine the Answer

A liquid is described as having a variable shape and compresses negligibly, based on the characteristics defined in the previous steps.

Key concepts

Liquid Properties

Liquids are one of the fascinating states of matter, often characterized by their ability to flow. A key property of liquids is their definite volume—they maintain the same volume regardless of the shape of their container. This means that if you pour 100 ml of water from a cylindrical glass to a conical glass, it will still occupy 100 ml in both situations.
However, the shape of the liquid is not fixed. It adapts to the container's shape. This flexibility is due to the molecules in a liquid being close enough to resist compression, yet not so tightly packed that they can't move past each other.

• Definite volume
• Variable shape
• Low compressibility

These properties make liquids unique when compared to solids and gases.

Physical State Characteristics

The physical states of matter—solid, liquid, and gas—each have distinct characteristics based on molecular arrangement and behavior.
Liquids have molecules that are packed closely but can slide past each other. This results in the fluidity that allows liquids to flow. In contrast, solids have a definite shape due to their tightly packed, vibrating molecules. Gas molecules are well-separated and move freely, giving gases no definite shape or volume.

These physical characteristics make it easy to distinguish between the different states. For liquids:

• Molecules are close but able to move
• Shape is determined by the container

The ability of the molecules to move while staying close enables the liquid's flow and adaptability in form.

Compression in Liquids

Compression refers to the ability of a substance to decrease in volume under pressure. Liquids are known for their negligible compressibility, which means that they do not significantly change volume when pressure is applied.
Unlike gases, which can be compressed easily due to the large spaces between molecules, liquid molecules are already close together. This close arrangement means there's little room for these molecules to be pushed closer without extreme pressure.

• Resistant to compression
• Molecules are already closely packed

Understanding the compression properties of liquids helps in many industrial applications, such as hydraulic systems and fluid dynamics.