Unit 3

Question 1

Eric notices that ice cubes float when you put them in a glass. This is because ice is less dense than liquid water. Explain what this suggest about the arrangement of the water molecules in each state.

Answer 1

There is a smaller mass in a given volume of ice than water. So the water molecules are further apart in ice than they are in liquid water

Question 2

State what is meant by the term physical change

Answer 2

A change where you don’t end up with a new substance/ same substance in a different form

Question 3

State what is meant by the term internal energy

Answer 3

The sum of the energy in the particles kinetic and potential energy stores

Question 4

State three things that the increase in a systems temperature depend on

Answer 4

Shc
Mass
Heating the object

Question 5

Define the term specific latent heat

Answer 5

The amount of energy required to change the state of 1kg of a substance with no change in temperature

Question 6

Picture a graph of a substance as it is heated. Explain in terms of particles why the graph is flat

Answer 6

As a substance is heated, it’s internal energy increases. As a substance melts,all of this energy is used to break apart intermolecular bonds so there is no increase in the substances temperature as it changes state

Question 7

What is the formula that links pressure and volume

Answer 7

PxV=constant

Question 8

Picture of syringe with some glue on the end so it is airtight. When the syringe is pressed, the gas is at a higher pressure. Using the particle model, define gas pressure and explain why the gas and the container is at a lower pressure when the syringes are not pressed.

Answer 8

A gas is made of particles. Particles collide with each other and the sides of the container they are in, which exerts a force on the side of the container. The total Force per unit area exerted on the container is the gas pressure.
As the volume is increased, gas particles spread out more. This means that there are fewer collisions with the side of the container so the gas pressure decreases.

Question 9

Explain how compressing air increases temperature until it’s hot enough to ignite some of the diesel fuel.

Answer 9

To compress air, work must be done. This work is done against the force caused by the pressure of the air in the piston. Energy is transferred to the internal energy of the system. So energy is transferred to the kinetic energy stores of the air particles. This increases the temperature of the air because temperature of a gas is related to the average energy in the kinetic stores of the gas molecule so doing work on the gas increases it’s temperature