Particle models and gas pressure

Which of the following best describes the arrangement and motion of particles in a solid?

Particles are close together in a regular pattern and vibrate about fixed positions. In a solid, particles are very close together, arranged in a regular pattern, and vibrate about fixed positions. They do not slide past each other or move freely.

A liquid has no definite shape but has a definite volume. Which property of liquids explains this?

Particles are close together but can slide past each other. In a liquid, particles are close together but can slide past each other, allowing the liquid to flow and take the shape of its container while maintaining a fixed volume.

A sealed piston is used to expand a gas at constant temperature. No gas escapes. What happens to the density and pressure of the gas?

Density decreases, pressure decreases. When a gas expands at constant temperature, its volume increases. Since mass is constant, density (mass/volume) decreases. According to Boyle's law, pressure is inversely proportional to volume, so pressure also decreases.

Which change of state involves particles moving much closer together but continuing to travel throughout the substance?

Condensing Condensation is the change from gas to liquid. In a gas, particles are far apart and move rapidly; when they condense, they move closer together but can still move around (slide past each other) in the liquid state.

A sealed rigid container of fixed volume is filled with air and placed in a freezer. The temperature of the air decreases. Which row correctly describes the changes?

Average distance between particles: no change; Average speed: decreases The container is rigid, so volume is fixed. Therefore, the average distance between particles does not change. As temperature decreases, the average kinetic energy decreases, so the average speed of particles decreases.

A balloon is filled with air and tied closed. It is placed in a refrigerator. As the temperature decreases, what happens to the average speed of the air molecules and the pressure inside the balloon?

Average speed decreases, pressure decreases. As temperature decreases, the average kinetic energy of the air molecules decreases, so their average speed decreases. The balloon's volume may decrease slightly, but the pressure also decreases because the molecules collide with the walls less frequently and with less force.

Brownian motion is observed when smoke particles are viewed through a microscope. What causes the smoke particles to move randomly?

Smaller air particles collide with the smoke particles. Brownian motion is caused by the random collisions of fast-moving air molecules (too small to see) with the larger smoke particles, causing them to move erratically.

A gas is heated in a closed container of constant volume. What happens to the particles of the gas?

They move faster. Heating the gas increases the kinetic energy of the particles, so they move faster. They do not expand individually; the volume is constant, so they do not get closer together; they hit the walls with greater force.

Which row gives the correct relative separation of particles for gas, liquid, and solid?

Gas: far apart, Liquid: close together, Solid: close together Gas particles are far apart, liquid particles are close together, and solid particles are close together. The correct order is gas: far apart, liquid: close together, solid: close together.

A car tyre is inflated with air. As the car drives, the temperature of the tyre increases, causing the pressure of the air inside to increase. Which is a correct explanation?

The average kinetic energy of the air molecules has increased. As temperature increases, the average kinetic energy of the air molecules increases. They move faster and collide with the tyre walls more frequently and with greater force, increasing the pressure.

A fixed mass of gas at constant temperature is compressed to half its original volume. What is the new pressure if the original pressure was P?

2P Boyle's law states that for a fixed mass of gas at constant temperature, pressure is inversely proportional to volume. If volume is halved, pressure doubles. Therefore, new pressure = 2P.

Which statement about absolute zero is correct?

Absolute zero is -273°C. Absolute zero is the lowest possible temperature, at which particles have minimum kinetic energy. It is equal to -273°C (or 0 K).

A fixed mass of gas is trapped in a cylinder with a movable piston. The gas is compressed slowly so that its temperature remains constant. The volume decreases from 200 cm³ to 100 cm³. If the initial pressure was 150 kPa, what is the final pressure?

300 kPa Boyle's law states that for a fixed mass of gas at constant temperature, pressure × volume = constant. So initial pV = 150 kPa × 200 cm³ = 30,000 kPa·cm³. Final volume = 100 cm³, so pressure = 30,000 / 100 = 300 kPa.

A sealed container of fixed volume is filled with air at 20 °C. The container is heated until the temperature reaches 100 °C. What happens to the pressure of the air?

It increases. At constant volume, increasing the temperature increases the average kinetic energy of the gas particles. They collide with the walls more often and with greater force, so the pressure increases.

A gas is at a pressure of 2.0 × 10⁵ Pa and a temperature of 27 °C. What is the temperature in kelvin?

300 K To convert from Celsius to kelvin, add 273. So 27 °C + 273 = 300 K.

Which arrangement has particles that move throughout the container and is easiest to compress?

The arrangement on the right The right-hand arrangement is a gas, with large spaces between particles, so it is easy to compress.

How would you design the inquiry for particle models and gas pressure?

Use a teacher-approved gas simulation to compare pressure at different volumes with a fixed temperature. Compare the volume occupied by the gas; record gas pressure; keep the gas amount and temperature constant.

What limitation matters when applying particle models and gas pressure?

An ideal-gas model becomes less accurate under conditions where particle interactions and finite size matter.