Particle model of matter Flashcards
To convert g/cm3 to kg/m3 you have to:
Multiply the g/cm3 value by 1000
per cm3 to per m3, multiply by 1,000,000 ( m3 = 1,000,000 larger)
What is the equation to calculate density?
Density = mass/volume
Unit for density?
kg/m³
Unit for volume?
m³
What is density?
A measure of how much mass a substance has per unit of its volume.
How would we calculate the density of a liquid experimentally?
-Place an empty measuring cylinder on a balance
-Zero the balance
-Pour the liquid into the cylinder
-Record it’s volume
-Record the mass of the liquid
-Use the density equation
How can we get more accurate estimates of density of a liquid?
Measure a larger volume.
Take multiple measurements to identify any anomalies and calculate a mean.
How would we calculate the density of a regular solid experimentally?
-Place the solid on a balance and measure the mass
-Find volume by measuring and then multiplying its length, width, and height
-Use the density equation
How would we calculate the density of an irregular solid experimentally?
-Place the solid on a balance and measure the mass
-Measure the volume by adding the solid to a Eureka can filled with water.
-Use the density equation
What is the symbol equation for density?
ρ = m/V
What can the particle model be used to explain?
-The different states of matter
-Differences in density
What is the arrangement and energy of the particles in a solid like?
-Particles are arranged neatly into ordered rows
-Particles are all closely packed and touching
-Particles vibrate in a fixed position (less kinetic energy)
Why are solids denser than liquids and gases?
The particles in solids are more tightly packed, with less space between them, than liquids or gases (the volume of solids is small).
So, density is higher because density is defined as mass per unit volume.
Why are particles in a solid in a regular lattice structure?
Strong forces of attraction between particles/bonds holds them close together.
Why are substances in the gaseous form less dense than liquids or solids?
The particles are widely spaced so the same number of particles occupies a larger volume than in a liquid or solid.
This leads to a lower density as density is defined as mass per unit volume.
Density of a liquid? (compared to a solid)
In a liquid, the particles are a bit more spread out, so the volume is slightly larger, resulting in a slightly lower density than a solid.
How do changes of state differ from chemical changes?
-They are physical changes
-The material recovers its original properties if the change is reversed
What is the arrangement and energy of the particles in a liquid like?
-Particles are arranged randomly
-Particles are less tightly compact than in solids
-Particles can move past each other (randomly)
What is the arrangement and energy of the molecules in a gas like?
-Molecules are arranged randomly
-Molecules are spread far apart
-Molecules are constantly moving with random motion (deflected randomly)
Why do molecules in a gas move around constantly, and very quickly?
They have a lot of kinetic energy.
What happens if we heat up a solid?
The particles gain more kinetic energy and so vibrate more.
Eventually, they will gain enough energy to overcome the strong forces of attraction holding them together.
This allows particles to break free of the solid lattice - ‘melting’.
This is known as the ‘melting point’.
What happens if we heat up a liquid?
The particles gain kinetic energy and so move around faster.
This weakens the forces of attraction holding the particles together.
At the ‘boiling point’, the particles have enough energy to break away from the forces all together - ‘evaporating/boiling’.
So, the liquid evaporates/boils into a gas.
What happens if we heat up a gas?
The particles gain kinetic energy and so travel faster.
If the container is expandable, gas will expand and so volume will increase
If the container is fixed, pressure will increase.
What happens if we cool down a gas?
The particles will lose kinetic energy and so won’t have enough energy to overcome the forces of attraction between them.
Bonds will start to form between the particles, condensing the gas in to a liquid.
What happens if we cool down a liquid?
The particles will lose kinetic energy and so won’t have enough energy to overcome the forces of attraction between them.
More bonds will start to form between the particles, fixing them in place and freezing the particles into a solid lattice.
Will changes in state change the mass of a substance in a closed system?
No because the number of particles doesn’t change
Will changes in state change the volume of a substance in a closed system?
Yes.
This is because solids have a higher density.
500kg of a solid melts into a liquid. What is the mass of the liquid?
500kg.
What is sublimation?
The conversion of a substance from a solid to a gas without it becoming a liquid e.g. the vaporisation of frozen carbon dioxide (dry ice).
What is internal energy?
Energy stored in a system by its particles.
What is the internal energy of a system made up of?
The total kinetic energy and potential energy of all the particles that make up a system.
How can internal energy be changed?
Heating
What is temperature?
A measure of the average internal energy of all the particles in a substance.
Explain what happens to internal energy when a substance is heated?
-Thermal energy is supplied to the particles in the system
-This causes the kinetic energy of the particles to increase
-So the internal energy of the substance increases
-This leads to a change in temperature
(The increase in energy can be calculated using the equation △E = mc△θ)
What happens to the internal energy of a substance when it changes state?
-There will not be a change in the kinetic energy of the particles (so temperature will not change)
-There will be a change in the potential energy of the particles
-So internal energy will increase
-This energy can be calculated using the equation E= m L
What happens as we heat objects?
-Internal energy of the particles increases
-The object’s temperature increases
Why does temperature remain constant when a change of state occurs? (heating)
When a substance is changing state, the energy provided is being used to overcome the bonds holding the particles together rather than increasing the particles kinetic energy.
Why does temperature remain constant when a change of state occurs? (cooling)
When a substance is changing state, the energy provided is being used to form new bonds between particles which releases energy and counteracts the energy lost in the cooling process.
What is specific latent heat?
The energy required to change the state of 1kg of a substance without changing its temperature
(The amount of energy released by a change in state)