2.1.1 States of matter (3)
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1.
Describe a simple experiment to demonstrate the difference in compressibility between solids, liquids and gases. Include in your description:
- The materials you would need.
- The procedure you would follow.
- What observations you would make.
- How you would explain your observations in terms of the arrangement of particles.
Materials:
- A small glass vial or container.
- A small amount of each substance: solid (e.g., a small pebble), liquid (e.g., water), and gas (e.g., air – trapped in the vial).
- A syringe (without a needle).
Procedure:
- Place a small amount of each substance separately into the syringe.
- Slowly and carefully attempt to compress each substance by pulling back the plunger of the syringe.
- Observe what happens to each substance as you try to compress it.
Observations:
- The solid will not compress significantly; it will maintain its shape.
- The liquid will compress very slightly; its volume will decrease a tiny amount.
- The gas will compress significantly; its volume will decrease considerably.
Explanation:
Solids: The particles in a solid are held in fixed positions and are very close together. There is very little space for them to move, so they cannot be easily compressed.
Liquids: The particles in a liquid are close together but can move past each other. There is a small amount of space between the particles, so the liquid can be compressed slightly, but not very much.
Gases: The particles in a gas are widely spaced and move randomly. There is a large amount of space between the particles, so the gas can be compressed significantly.
2.
A student is asked to describe the differences between solids, liquids and gases. State three distinguishing properties of each state of matter.
Solids:
- Fixed shape and volume.
- High density.
- Particles are closely packed in a regular arrangement.
Liquids:
- Variable volume, but fixed shape (takes the shape of the container).
- High density (generally, but less than solids).
- Particles are close together but can move past each other.
Gases:
- Variable volume and shape (fills the entire container).
- Low density.
- Particles are widely spaced and move randomly.
3.
A scientist is conducting an experiment to study the properties of matter. They have three samples: a solid, a liquid, and a gas.
(a) State the key difference between a solid, a liquid and a gas in terms of their particle arrangement.
(b) Explain why a gas is compressible, while a solid is not.
(a)
A solid has particles arranged in a fixed, ordered pattern. A liquid has particles that are close together but can move past each other. A gas has particles that are far apart and move randomly.
(b) Gases are compressible because the particles are widely spaced. This allows the space between the particles to be reduced by applying pressure. Solids are not compressible because their particles are tightly packed in a fixed arrangement, leaving little or no space for compression.