3 - Particle model of matter

What is the use of a particle model?

What is the use of a particle model?

The particle model is widely used to predict the behaviour of solids, liquids and gases, and help explain observations

What is the equation for density?

Density = mass divided by volume

What is density measured in?

Kilograms per metre cubed (kg/m^3)

What is volume measured in?

Metres cubed (m^3)

What can he particle model be used to explain?

The particle model can be used to explain the difference states of matter, and the differences in density

Draw a diagram for a solid

Draw a diagram for a liquid

Draw a diagram for a gas

Explain the differences in density between the different states of matter.

Solids > Liquids > Gas

Why are solids the most dense, based on arrangement of atoms or molecules?

Particles are tightly held tgt in a fixed positions so the space between is less, making them more dense that liquids or gases

Why are liquids less dense, based on arrangement of atoms or molecules?

Particles are close in contact , but not in fixed position (further apart)- they can move, slide past each other and flow so they are less dense than solids, but more than gases

Why are gases the least dense, based on arrangement of atoms or molecules?

Atoms or molecules are spread out and move randomly- they are further apart making them less dense than solids or liquids

How is mass conserved when substances change state?

When a substance changes state, the number of particles is the same so mass is conserved (mass before = after)

What type of changes (physical or chemical) are changes of state?

Physical

Why are physical changes of state different from chemical?

Because the material recovers its original properties if the change is reversed

Where is energy stored?

Energy is stored inside a system by the particles (atoms and molecules) that make up the system - Internal Energy

What is internal energy?

Internal energy is the total kinetic energy and potential energy of all the particles (atoms and molecules) that make up a system.

How does heating change the energy stored within the system?

Heating changes the energy stored in the system by increasing the energy of particles in it - this either raises the temp, or produces a change of state

What does the increase in temperature of a system depend on?

The mass of the substance heated, they type of material and the energy input to the system

What is the equation for the change in thermal energy using specific heat capacity?

Change in thermal energy = mass x specific heat capacity x temperature change

What is the specific heat capacity?

The specific heat capacity of a substance is the amount of energy required to raise the temperature of one kilogram of the substance by one degree Celsius.

What is latent heat?

The energy needed for a substance to change state

What happens to the energy stored and the temperature when a change of state occurs?

When a change of state occurs, the energy supplied changes the energy stored (internal energy) but not the temperature.

What is specific latent heat?

The specific latent heat of a substance is the amount of energy required to change the state of one kilogram of the substance with no change in temperature.

What is the equation for the energy for a change of state using specific latent heat?

Energy for a change of state = mass x specific heat

What are the units for specific latent heat?

Joules per kilogram (J/kg)

What is the specific latent heat of fusion?

Change of state from solid to liquid

What is the specific latent heat of vaporisation?

change of state from liquid to vapour

Interpret heating and cooling graphs, including changes of states - ice

The temperature of the water increases till 0, where it starts to melt, then stays constant till the ice has melted, then increases from 0 - 100 until water starts to boil, then stays constant at 100 as the water turns to steam

What motion are the molecules of gas constantly in?

The molecules of a gas are in constant random motion.

What energy is the temperature of a gas related to?

The temperature of the gas is related to the average kinetic energy of the molecules.

What does changing the temperature of a gas also change?

Changing the temperature of a gas, held at constant volume, changes the pressure exerted by the gas.

How is the motion of the molecules in a gas related to its temperature?

Heating a gas makes the particles move move faster on avg, so the particles collide with the surface more often and with more force

How does the motion of the molecules in a gas relate to its pressure?

When gas particles move they collide w each other and the surface - each impact exerts a force, and many impacts happen - the total force exerted on a unit area increases, so the pressure increases

Explain the relationship between the temperature of a gas and its pressure (at constant volume)

As the temperature increases, the pressure increases - Heating a gas increases the pressure, as energy is transferred to their particles and they gain kinetic energy - they move faster on avg, so the particles collide with the surface more often and with more force

How can gases be compressed or expanded?

A gas can be compressed or expanded by pressure changes.

What does pressure produce on the walls of the gas container?

The pressure produces a net force at right angles to the wall of the gas container (or any surface).

How does increasing the volume in which a gas is contained, at constant temp lead to a decrease in pressure?

If the volume increases, the space the molecules move in is bigger, so they travel further between each impact - the molecules hit the surface less often, so the no of impacts per sec decreases - total force of impacts per sq metre (pressure) decreases

For a fixed mass of gas held at constant temperature, what is pressure x volume?

Pressure x volume = constant

What are the units for pressure?

Pascals

What is work the transfer of?

Work is the transfer of energy by a force.

What happens to the internal energy and temperature of a gas when work is done on it?

Doing work on a gas increases the internal energy of the gas and can cause an increase in the temperature of the gas.

In a bicycle pump, how doesn't doing work on an enclosed gas lead to an increase in temperature of the gas?

Applying force on the pump does work, overcoming the force caused by the pressure of the gas - this decreases the volume as gas is compressed - the force transfers energy to it, which increases the kinetic energy of its molecules, so they move faster, colliding w each other and the walls more often and with greater force, so the temp increases