Particle Model & Pressure Flashcards

All 27 cards in this deck

What causes the pressure of a gas on the walls of its container?

Gas particles colliding with the walls; each collision exerts a force on the wall.

How do the particles of a gas move, according to kinetic theory?

Randomly, in all directions, at high speeds and with a range of speeds.

In which direction does the force produced by the pressure of a gas act on a surface?

At right angles ($90\degree$ / perpendicular / normal) to the surface.

What happens to the pressure of a fixed mass of gas kept at constant volume when its temperature is increased?

The pressure increases — particles move faster, so they hit the walls more often and harder.

True or false? The pressure a gas exerts on its container is caused by the particles colliding with each other.

False. It is caused by particles colliding with the walls of the container.

True or false? Increasing the temperature of a gas increases the average kinetic energy of its particles.

True. Higher temperature means faster-moving particles.

What is absolute zero in degrees Celsius?

$-273\degree\text{C}$ (0 K).

Describe absolute zero in terms of the particles of a substance.

The temperature at which particles have no movement (minimum possible kinetic energy).

What is the rule for converting a temperature in degrees Celsius to kelvin?

Add 273: temperature in K = temperature in $\degree$C $+\ 273$.

What are the steps to convert a temperature in kelvin to degrees Celsius?

e.g. 350 K

1. Subtract 273 from the kelvin value: $350 - 273$
2. Give the answer in $\degree$C: $77\degree\text{C}$

True or false? A temperature can be lower than 0 K.

False. 0 K is absolute zero, the lowest possible temperature.

True or false? A temperature rise of 1 K is the same size as a temperature rise of $1\degree$C.

True. The kelvin and Celsius scales have the same size divisions, just a different zero.

What happens to the rate of collisions with the walls and to the pressure when a fixed mass of gas is squeezed into a smaller volume at constant temperature?

Particles hit the walls more often, so the pressure increases.

What happens to the pressure of a fixed mass of gas at constant temperature when its volume is increased?

The pressure decreases — the particles are more spread out, so they collide with the walls less often.

Why can a gas be compressed?

Its particles are far apart with large spaces between them, so increasing the pressure pushes them closer together.

What happens to a fixed mass of gas if the pressure on it is reduced at constant temperature?

It expands — its volume increases.

True or false? When a gas is compressed at constant temperature, its particles move faster.

False. Particle speed depends on temperature; they simply hit the walls more often in the smaller space.

True or false? Pulling out the piston of a sealed syringe increases the mass of gas inside it.

False. The mass stays the same; the volume increases and the pressure decreases.

What is the equation linking pressure and volume for a fixed mass of gas at constant temperature?

$P_1 \times V_1 = P_2 \times V_2$

Under what conditions can $P_1 \times V_1 = P_2 \times V_2$ be used?

For a fixed mass of gas kept at constant temperature.

How are the pressure and volume of a fixed mass of gas at constant temperature related?

Inversely — doubling the pressure halves the volume.

What are the steps to find a new volume using $P_1 \times V_1 = P_2 \times V_2$?

e.g. 6 litres of gas at 100 kPa is compressed to 300 kPa

1. Substitute: $100 \times 6 = 300 \times V_2$
2. Rearrange: $V_2 = \dfrac{100 \times 6}{300}$
3. Evaluate: $V_2 = 2$ litres

True or false? In $P_1 \times V_1 = P_2 \times V_2$ the volumes must always be converted to $\text{m}^3$.

False. Any volume unit works as long as $V_1$ and $V_2$ are in the same unit (and $P_1$, $P_2$ in the same unit).

Why does the air in a bicycle pump get warm when you push the plunger in?

Work is done compressing the air, which increases the kinetic energy of its particles, so its temperature rises.

What does 'doing work on a gas' mean?

Transferring energy to the gas by a force compressing it, increasing the gas's internal (thermal) energy store.

True or false? The air in a bicycle pump warms up only because of friction between the plunger and the barrel.

False. Even with no friction, the work done in compressing the air raises its temperature.

True or false? A gas can get hotter without any heating, if work is done on it.

True. Compressing a gas transfers energy to its particles, raising its temperature.