Flashcards in The Particle Model of Matter Deck (71)
How was the detailed and experimentally confirmed particle model of matter devised?
After many years of development (stemming from Boltzmann and Einstein), through the collaborative work of many, many scientists, peer reviewing and collaborating each other's work
What three key things is the particle model of matter used to explain?
-States of matter
-Density of materials
-Pressure and behaviour of gases
Describe the arrangement, bonds and density of a solid
-Rigid bonds between particles
-Denisty of 10^3 kg/m^3
Describe the arrangement, bonds and density of a liquid
-Flexible bonds between particles
-Denisty of 10^3 kg/m^3
Describe the arrangement, bonds and density of a gas
-No bonds between particles
-Density of 10^-1 kg/m^3
Describe the behaviour of particles in a solid:
They can only vibrate if given kinetic energy
Describe the behaviour of particles in a liquid:
They can take the shape of the container
Describe the behaviour of particles in a gas:
They move to fill up the container
What is a system?
A collection of particles
How is the internal energy of a system defined?
As the sum of the particles' kinetic and potential energies
What is the kinetic energy of a particle associated with?
-The energy associated with movement so therefore:
-Associated with the temperature of the system (temperature is proportional to the average kinetic energy)
What is the potential energy of particles associated with?
-Their configuration so therefore:
-The state of the system
What is fusion?
Liquid to a solid
What is vaporisation?
Liquid to a gas
What energy transfers can result in a change of state?
-The change in pressure and volume
How do you calcualte density?
How do you calculate the change in internal energy resulting in a change of temperature?
Energy transferred = mass x specific heat capacity x temperature change of the system
How do you calculate the change in internal energy resulting in a change of state at a constant temperature?
energy transferred = specific latent heat x mass that changes state
How do you calculate the percentage difference to evaluate data?
((measured-true)/(true) ) x 100
What do you conclude when your results are within 10% of the actual data?
Data can be considered to be within the bonds of experimental probability
Plan an experiment which would allow someone to measure the density of an irregular shaped object
-Measure the mass of the object using a top pan balance
-Fill a measuring cylinder partly with water and measure the initial volume
-Place the object into the measuring cyclinder and measure the new volume
-Work out volume of object by doing new volume-initial volume
-Substitute volume and mass values into density equation
-Repeat the experiment multiple times to calculate a mean density
What did Einstein's explanation of Brownian Motion result in?
A kinetic theory describing the motion of particles
How did Einstein explain the random motion of visible particles?
They result from random motion of invisble particles causing them to collide with the visible particles
What is the relationship between temperature and average kinetic energy of particles?
Temperature is proportional to the average kinetic energy of a particle or a system of particles
Describe and explain the concept of absolute zero (0 kelvin):
If temperature is proportional to the average kinetic energy of a particle, when temperature reaches the lowest point possible (0K), the kinetic energy of particles in a system is zero
How is pressure exerted on a surface or a container by a system of particles?
Pressure is exerted as a result of collisions between the particles of the system and the walls of the container or the surface
How do you calculate momentum? What does this demonstrate?
Momentum = Mass x Velocity
Shows us that moving, massive particles have momentum
What is the rule about momentum?
Momentum is transferred but overall, remains constant (conserved in a closed system)
What does Newton's second law of motion explain?
Force = rate of change pf momentum
F = Δp/Δt
What factors increase pressure?
-Reducing volume of container with system of particles
-Increasing the number of particles
Explain how the factors which increase pressure, actually do so:
-These factors mean a greater rate of collisions
-This results in the greater the rate of change of momentum
-Following Newton's second law of motion, this results in a greater force which the partcle exerts on the wall
-And consequntly, greater the pressure
What is the equation for calculating pressure?
Pressure = Force/ Area
P = F/A
What is the relationship between the rate of change of a particle's momentum and that of the rate of change of momentum of the surface with which the particle collides?
It is equal in magnitude but opposite in direction
What unit is pressure measured in?
What does Boyle's Law state?
Pressure is inversely proportional to volume
p ∝ 1/V
Explain Boyle's law in terms of particles in a system?
- If the volume of the container is decreased
-Particles travel a shorter distance between collisions
-Therefore the rate of collisions increases
-And thus, pressure increases
How do you calculate denisty?
ρ = m/V
From Boyle's law, Charles' Law and the Pressure law, for a gas of fixed mass at a constant temperature, what can we say?
pressure x Volume = constant for a fixed number of particles at a constant temperature
Ice has a lower density than water. This means that it should float in water. Steel has a density significantly higher than water. However, a steel ship still floats. Suggest how this is possible.
The steel hull of a ship contains a large volume of air. This means that the average density of a ship is lower than the average density of water. This allows steel ships to float
What is the name of the force which keeps an object afloat?
When does an object float on a fluid?
When its density is lower than that of the fluid
What is the Law of Displacement?
A law which states that an object completely submerged in a fluid will replace an amount of fluid equal to its own volume.
How does the electronic arrangement of an atom change when it absorbs electromagnetic radiation?
When atoms absorb electromagnetic radiation, electrons move to a higher energy level further away from the nucleus.
How does the electronic arrangement of an atom change when it emits electromagnetic radiation?
When atoms emit electromagnetic radiation, electrons move to a lower energy level, closer to the nucleus
What are the three important concepts to bear in mind with changes of state?
-Mass is conserved
-Process is reversible
-Physical (not chemical) process
What is the pressure law?
Pressure is proportional to temperature
p ∝ T
Describe the pressure law in terms of particles:
-As temperature increases, the kinetic energy of the particles increases
-so the velocity of the particles increases
-so the time between collisions decreases
-Rate of collisions increases
The additional pressure at a depth, h, below the surface of a fluid of density, ρ, is given by what equation?
p = ρgh
p= additional pressure due to a fluid
ρ= density of fluid
g = acceleration due to gravity
h = depth below the surface of fluid
Why is the pressure of water greater at the bottom of the sea?
-The greater depth under the water
-the greater the weight of the water
-greater the pressure
Why does popcorn pop when heated?
-A thermal energy transfer takes place from heat source to the popcorn
-The kernels contain water
-The water in the kernels turns to steam
- Steam occupies a greater volume than water
-Steam pushes against casing, exerting a pressure, and opens up the weakest part of the kernel
-Kernel turns inside out (pops) and corn expands
What are the two names for a change of state from liquid to a gas?
Vaporisation and boiling
Why is liquid a more energetic state than a solid?
Has more kinetic energy as particles are moving faster
Has more potential energy as there are larger gaps between particles
Why are the densities of liquids and solids similar?
Density is mass/ volume.
Similar masses due to similar numbers of particles
Particles are touching in both models
Volume of container is fixed so remains the same for both states
What happens to the mass when a substance changes state?
It stays the same (is conserved)
Why are changes of state physical changes?
No new substances are formed and they are reversible
What is the difference between boiling and vaporisation?
Boiling point occurs throughout a liquid at its boiling point but vaporisation occurs from the surface of a liquid at a temperature at or below its boiling point
What can be used to explain why a substance is a solid, liquid or gas?
The strength of forces of attraction between the particles
What increases when you heat a substance and its temperature rises?
The kinetic energy of its particles
What increases when you heat a substance and its temperature does not rise?
The potential energy of its particles
What is the energy being used for during a change of state (increase in internal energy) ?
To break or weaken bonds (so not to increase kinetic energy and thus temperature)
Compare latent heat and specific latent heat
Latent heat is the energy needed to change the state of a substance, it is measured in J. Specific latent heat is the energy required to change 1kg of the substance and is measure in J/kg.
Why is the specific latent heat of vaporisation higher than the specific latent heat of fusion?
-When heating a substance and changing its state, you increase the potential energy (not kinetic) of the substance's particles
-this requires more energy per kilogram for a liquid to gas (vaporisation) than a solid to a liquid (fusion)
-because bonds are being completely broken in vaporisation between the particles
What was the piece of evidence for the random motion of gas molecules?
Brownian motion/ smoke particles being moved by air particles we cannot see
How is pressure affected when a gas is compressed?
How is pressure affected when a gas is allowed to expand?
What is done to a gas when compressed ?
What happens when work is done on a gas quickly? Why?
The internal energy of the particles increases as the kinetic energy and thus temperature increases. There is no time for cooling by transferring energy to the surroundings if done quickly
Why does a can become colder if gas is allowed to escape from it rapidly?
The gas expands as it escapes
Does work on air (pressure)
Decrease in the internal energy of the gas and can
Due to no time for energy transfer to equalise the temperature
Describe the movement of a gas:
-range of speeds
-moving in different directions
Explain what led to the plum pudding model of the atom being replaced by the nuclear model of the atom:
-alpha particle scattering experiment
-alpha particles directed at gold foil
-most alpha particles pass straight through
-(so) most of atom is empty space
-a few alpha particles deflected through large angles
- (so) mass is concentrated at centre of atom
-(and) nucleus is (positively) charged
- plum pudding model has mass spread throughout atom
- plum pudding model has charge spread throughout atom