Topic 3: Particle Model of Matter Flashcards
The equation for density?
Density (kg/m^3) = Mass (kg) / Volume (m^3)
Three states of matter?
Solid, Liquid and Gas
Describe a solid
Strong forces of attraction
To hold particles in a fixed, regular position
Not much energy, so they can only vibrate about their positions.
DEnsity is generally the highest.
Describe a liquid
Weaker forces of attraction between the particles
They are close together but can move past each other, and form irregular arrangements
More energy than particles in solids
They move in random directions at low speeds
Generally less dense than solids
Describe a gas
Almost no forces of attraction between the particles.
They have more energy than in liquids or solids - they’re free to move and travel in random directions at high speeds.
Generally less dense than liquids and have low densities.
To find the density of a solid:
Use a Eureka can full of water and measure the water displaced once the solid is placed in it.
Record the volume of water and calculate density from the mass of the object.
To find the density of a liquid:
Place a measuring cylinder on a balance
Pour 10ml of the liquid into the measuring cylinder and record the mass of the liquid
Pour another 10ml into the cylinder, repeating the process until the cylinder is full and recording the total volume an mass each time.
For each measurement, find the density and take an average.
The energy stored in a system is…?
Stored by its particles (atoms and molecules)
The internal energy of a system is…?
The total energy that its particles have in their kinetic and potential energy stores.
Heating the system…?
Transfers energy to its particles (they gain energy in their kinetic stores and move faster), increasing the internal energy.
Changes of state?
Freezing Melting Boiling/Evaporating Condensing Sublimating (Solid - Gas) Desublimating (Gas-Solid)
A change of state is a…?
Physical change (rather than a chemical one) meaning its not a new substance, just the same one in a different form.
When changing state…?
Mass is conserved.
When a substance is melting or boiling…?
You’re still putting in energy and so increasing the internal energy, but the energy’s used for breaking intermolecular bonds, rather than raising the temperature. Which is why there are flat spots on the heating graph.
When a substance is condensing or freezing…?
Bonds are forming between particles, which releases energy. Meaning that the internal energy decreases, but the temperature doesn’t go down until all the substance has turned to a liquid (condensing) or a solid (freezing)
The energy needed to change the state of a substance is…?
Latent heat
Specific Latent Heat is…?
The amount of energy required to change 1kg of an object from one state to another without changing its temperature.
The formula for specific latent heat?
Energy (J) = Mass (kg) x SLH (J/kg)
E = mL
The temperature of a gas is related to…?
The average energy in the kinetic energy stores of the particles in a gas.
The higher the temperature…?
The higher the average energy
As you increase the temperature of a gas, the average speed of its particles increases. This is because the energy in the particles’ kinetic energy stores in 1/2mv^2
Describe how colliding gas particles create pressure.
As gas particles move about at high speeds, they bang into each other and whatever else happens to get in the way.
When they collide with something they exert a force (and so a pressure) on it.
In a sealed container, the outward gas pressure it the total force exerted by all of the particles in the gas on a unit area of the container walls.
Faster particles and more frequent collisions both lead to an increase in net force and so gas pressure. Increasing temperature will increase the speed, and so the pressure (If the volume is kept constant)
Pressure and volume are…?
Inversely proportional - when the volume goes up, the pressure goes down.
For a gas of fixed mass at a constant temperature, the relationship is…?
pV = constant p = pressure (pascals Pa) V = volume (m^3)
The pressure of a gas causes a…?
Net outwards force at right angles to the surface of its container
