Particles levels 7-9

Question 1

Compare the intermolecular forces in solids, liquids and gasses.

Answer 1

Solids have strong intermolecular forces. This means the particles are held in a fixed postion

Liquids have weak intermolecular forces that can break and be re-formed. This means that the particles can move past each other but cannot move apart

Gasses have not intermolecular forces between the molecules. This means that they can move freely.

Question 2

What is the pressure law (Gay-Lussacs law)?

What is the equation for the pressure law?

Sketch a graph for the pressure law?

Answer 2

The pressure law states that for a gas a at a constant volume the pressure is directly proportional to the temperature

The quation for the pressure law is:

Question 3

What is the relationship between density and state of matter?

Answer 3

Solids have a high density. This is becuase they have strong intermolecular bonds that are holdind the particles close together

Liquids have a fiarly high density. This is becuase the liquid has weak bonds between them, so some

Question 4

Explain why the density of a material changes when it changes state

Answer 4

The density of a material changes when it changes state becuase the particles get closer together or further apart. As density = mass/volume when the particles get further apart you have the same mass in a larger volume, so the density goes down. Similarly when the particles get closer together, you have the same mass in a smaller volume so density increases.

Question 5

Explain why boyle’s law occurs in terms of particle movement and forces.

Answer 5

Boyles law states that for a gas at a constant temperature, when the volume reduces the pressure increases, and when the volume increases the pressure reduces. This is becuase of the number of particles that are hitting the wall at any time. At a higher volume the surface area of the gass is greater, this means that the particles are hitting the wall over a larger area, so the pressure goes down. The larger volume means that particles spend more time in the centre of the gas, rather than colliding with the side.

Conversely, when the volume is smaller the particles hit the walls more frequently and over a smaller area, so the pressure goes up

Question 6

Explain how to calculate the pressure of a gas when the volume changes.

Example calculation: If the pressure of a gas is 30Pa at a volume of 35m², what is the pressure when the volume has been reduced to 5m².

Answer 6

To answer problems using gas laws, you need to use the starting pressure and volume to find the constant. You then use the constant to find the new pressure and volume.

Example calculation:

Question 7

What is Charles’ law?

What is the equation for Charles’ law?

Sketch a graph for Charles’ law

Answer 7

Charles’ law state that for a gas at a constant volume, pressure is proportional to temperature (as long as temperature is in kelvin and not in degrees centigrade)

The equation for the Charles’ law is:

Question 8

Explain how to conduct an experiment to find the value for absolute zero

Answer 8

To find the value of absolute zero you attach a pressure guage to a sealed container containing gas and heat up the container, measuring how the pressure changes with temperature.

You then plot a graph of temperature in ^oC against pressure and extrapolate the line back until it intercepts the x axis. At this point the gas has no pressure becuase the particles are not moving, so this is the lowest temperture that it is possible to get.

This value is -273.15^{<span>o</span>}C