2. Thermal physics (9-11) Flashcards
distinguishing properties of solids, liquids and gases & terms for the changes in state
solid- rigid, fixed shape, fixed volume, can’t be squashed, does not take shape of container
liquid- not rigid, no fixed shape, fixed volume, can’t be squashed, takes shape of container
gas- not rigid, no fixed shape, fixed volume, can be squashed, EXPANDS to fill its container
Describe the particle structure of solids, liquids and gases in terms of the arrangement, separation and motion of the particles
solid- packed closely in regular pattern, vibrate about fixed position because of strong intermolecular forces
liquid- packed slightly less closely and arranged randomly, vibrate and move around, slide past each other
gas- widely separated, move freely bouncing off one another
what affects the properties of solids, liquids and gases. density and energy highest to lowest
the forces and distances between particles (atoms, molecules, ions and electrons) and the motion of the particles affects the
properties of solids, liquids and gases
Density- solid, liquid, gas (volume less in solid)
Energy- gas, liquid, solid (strong intermolecular forces in solid)
fixed points
celsius scale has two fixed points- known values to calibrate a measuring instrument
0- melting point of pure ice at atm p
100- boiling point of pure water at atm p
lowest possible temperature
there is a lowest possible temperature (−273°C), known as absolute zero, where the particles have least kinetic energy
T (in K) = θ (in °C) + 273
Describe the pressure and the changes in pressure of a gas
the particles move around inside its container bumping into the sides. the gas causes pressure on walls of container because the gas particles are constantly colliding. change in momentum greater
these collisions produce a net force to the walls of gas container so a gas at higher pressure has more force exerted per unit area and more frequent collisions.
Describe qualitatively, in terms of particles, the effect on the pressure of a fixed mass of gas of:
(a) a change of temperature at constant volume
(b) a change of volume at constant temperature
relationship between pressure and volume
temperature inc- more kinetic energy so particles move faster and hit walls of container more often and with greater force. pressure inc
volume dec- gas particles compressed into a smaller space so they collide more often and pressure inc
greater rate of change of momentum per unit area on walls
molecules hit walls more often
molecules travel shorter distance between collisions with walls
pV = constant for a fixed mass of gas at constant temperature
p-y axis and v- x axis inversely ( C )
P-y axis and 1/v- x axis direct ( / )
evidence for the kinetic particle model of matter, define AND describe brownian motion
random motion of microscopic particles in a suspension is evidence for the kinetic particle model of matter
BM- the motion of small particles suspended in a liquid or a gas caused by molecular bombardment.
- moving particles are constantly knocked about by the fast-moving molecules of air.
- particles follow random path, frequently changing direction because air molecules repeatedly hit the smoke particle.
- the air molecules are light but fast moving so have enough kinetic energy to cause the smoke particle change direction on impact.
describe thermal expansion of solids, liquids and gases at constant pressure
increase in volume of a material when temperature increases
when a material expands, its particles do not get any bigger. Due to an increase in temperature they have more kinetic energy so particles can move around more and take up more space, this separation of particles makes the substance bigger
Explain, in terms of the motion and arrangement of particles, the relative order of magnitudes of the expansion of solids, liquids and gases as their temperatures rise
gas expand the most- its particles move about rapidly when heated, and it is easy for them to push walls of container further apart, so the gas takes up more space
solids expand the least- strong electrostatic force of attraction holding molecules together
relationship between temperature and energy of particles
a rise in the temperature of an object increases its internal energy.
an increase in the average kinetic energies of all of the particles in the object
Define specific heat capacity
quantity of thermal energy needed to raise temperature of an object per degree Celsius 1 °C. the energy required per unit mass per unit temperature increase
c = ∆E/m∆θ
heating causes particles to gain K.E and speed up. it takes more energy to raise the temperature of a large amount of water because more particle need to have their speed changed.
Describe melting and boiling in terms of energy and change in state
M- temperature at which a solid melts to become a liquid
B- temperature at which liquid changes to a gas at constant pressure
AT MP or BP, even if more thermal energy is added, the S/L doesn’t get warmer. The addition energy goes into overcoming intermolecular forces bw molecules of S/L, so thermal energy is not rising.
Describe condensation and solidification in terms of particles
Particles lose K.E and move more slowly, they no longer have enough energy to overcome the intermolecular forces of attraction bw molecules. The particles get closer. they only have enough energy to vibrate about their fixed position/ flow over one another
Describe evaporation
more energetic particles escape from the surface of a liquid. the particles that remain are those with less energy so the particle of liquid have less energy on average so the temperature of the water decreases and water cools down.
cooling of an object in contact with an evaporating liquid as the liquid cools down, solid cools down too. this is used in refridgerators and air conditioning units.
