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29 Cards in this Set
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define phase |
it is whether a substance is a solid liquid or gas |
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define density |
mass per unit volume |
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what is standard temperature and pressure (STP) |
273 K (0 degrees) and 100kPa (atmospheric pressure) |
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compare solids to liquids to gases |
solids and liquids are of the order of 1000 times denser than gasses
solids are usually a little denser than their liquids
changing pressure and temperature will not change the densities of solids and liquids much. but it will usually have an effect on gasses! |
talk about densities |
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what is the atomic molecular ordering of solids liquids and gasses? |
solid- molecules/ions packed in a solid are fixed in position.liquid- molecules are packed closely together but they are still able to slide past each other.gas- there is no arrangement at all, it is "chaotic" |
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compare the patterns of movement of molecules in solid liquids and gasses also what effect heating them has |
as a solid is heated, the kinetic energy of it's molecules increase, but their positions are still fixed
in a liquid, the same effect happens, although some of the heat energy can be transformed into translational kinetic energy and molecules will be able to move around more easily
with gasses, all the heat energy is transformed into translational kinetic energy |
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explain brownian motion |
it is the rapid, random motion of particles in a fluid (gas or liquid)
examples: pollen grains in water "shuddered" around instead of remaining still
smole particles in air also shuddered when viewed under a microscope
this proved that there must be molecules which they keep bumping into
this only happens with small particles since the molecules do not hit them equally from all sides, so impulse gained by the particles is not zero. (this wouldn't be the case if a large particle was used instead) |
pollen smoke |
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define pressure |
force per unit area Measured in pascals |
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state the assumptions made for the kinetic model of a gas |
the volume of particles is negligible to the volume of the container
the molecules move with rapid random motion
collisions between particles and particles and the wall of the container are all elastic
gravitational force of the particles is negligible
no intermolecular forces are acting between molecules |
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define internal energy |
the sum of the random distributions of kinetic and potential energies of all the molecules in a body |
key words!!!1 random |
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define ideal gas |
a gass that has an internal energy only in the form of random kinetic energy |
only in the form of... |
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state and explain some factors that effect internal energy |
temperature a temperature rise will result in a rise in kinetic energy, therefore a rise in internal energy.
pressure a fall in pressure with no change in temperature will not effect the internal energy of an ideal gas. if the gas isn't ideal, and the gas is expanding, there must be some work done to pull the (that are attracted to each other)
state this includes what phase a system has as well as it's crystalline structure and atomic arrangement a change in state doesn't involve a change in temperature, therefore kinetic energy doesn't change however the molecules random potential energies do change. (i.e. steam would have a greater potential energy than water) for most substances changing a solid to a liquid at the same temperature involves an increase i volume and a consequent rise in internal potential energy. water is unusual in terms of it's liquid form being denser than it's solid form. there is a rise in internal energy as ice melts.
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state two factors that have no effect on internal energy |
the speed of the whole body doesn't contribute
a change in position of the whole body in a gravitational field also doesn't contribute |
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define thermal equilibrium |
two objects at the same temperature will be in thermal equilibrium |
thermal =heat EQUALibrium |
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state the conditions of thermal equilibrium |
this applies to two objects when there is zero resultant energy transfer between them. this will happen when the temperatures of the two objects are equal. Temperature determine the direction in which thermal energy is transferred, which is from hotter temperatures to cooler temperatures. |
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what 3 things must you know about the absolute scale of temperature? |
- it exists -it doesn't depend on the property of a substance -it starts at zero, absolute zero (the temperature which a substance has a minimum internal energy) |
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explain absolute zero and the triple point of water |
absolute zero (where molecules have minimum kinetic energy)is 0K the triple point of water (where water exists as a solid, liquid and gas simultaneously) is exactly 273.16K |
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Define Specific Heat Capacity (s.h.c.) |
it is the quantity of thermal energy required to rise the temperature of a unit mass of a substance by a unit temperature rise.
the symbol for s.h.c. is c |
c=E/m(delta)(theatre)
E is the quantity of thermal energy required, m is the mass of the heated material and (delta theatre) is the change in temperature |
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define the specific latent heat of fusion of a substance |
it's the quantity of energy per unit mass required to change it at constant temperature from a solid to a liquid |
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define the specific latent heat of vaporisation of a substance |
it's the quantity of energy per unit mass required to change it at constant temperature from a liquid into a vapour |
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define Boyle's law |
it states that the volume of a fixed mass of gas is inversely proportional to the pressure exerted on it, provided the temperature is kept constant |
v(alpha) 1/p |
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explain an experiment used to demonstrate Boyle's law |
A piece of apparatus which consists of a long tube closed at one end and containing air above some oill. The pressure on the oil can be increased by pumping more air into the tube, the volume of the air can be measured on a scale behind the tube.
-the apparatus can be pumped up to high pressures then very slowly vented as the pressure gauge reads the values given, the volume is recorded -it's important to do the experiment slowly to keep a constant temperature (as gas cools it expands) -the unit for pV is Nm. the volume needs to be in m^3 and the pressure in Pa. -it's difficult to check the shape of the graph showing inverse proportion if p is plotted against v. So plot a p again 1/V graph. a straight line should be obtained to show pV is constant -the pressure gauge records total pressure. atmospheric pressure is 1x10^5 some suction may be required |
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define the ideal gas temperature |
for a fixed mass of an ideal gas at constant pressure, its volume V is proportional to the ideal gas temperature T in kelvins. |
K |
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even though ideal gasses are imaginary, what happens to certain gasses such as hydrogen and helium at low pressures? |
they behave like ideal gasses due to the spacing of their molecules |
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what is the Avogadro constant? |
Na (Avogadro's constant) has a value of 6.02x10^23 mol^-1
it is used to determine the number of moles in any quantity of any substance |
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What is the mole? |
a mole of any substance contains 6.02x10^23 (to 3s.f.) particles/molecules/atoms
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what is the molar gas constant? |
pV/T=nR where R is the molar gas constant with a value 8.3145Jmol^-1K^-1
pV=nRT
R is the gas constant for one mole of molecules
T is temperature in kelvin |
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wha is the Boltzmann constant? |
the gas constant for a single molecule unit k
it's used when considering the gas equation for molecules rather than moles. k is the gas constant for a single molecule
T is temperature in kelvin
pV=NkT where N is the number of molecules |
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what is the kinetic energy of a gas molecule? |
E=3/2kT
giving the mean random translational energy of an ideal gas. energy is directly proportional to temperature in kelvins |
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