8: Solids, gases, and liquids Flashcards
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ideal gas behavior
- Because ideal gases have zero volumes, gases under low pressure conform more closely to the ideal gas law than gases under higher pressure. both act similarly at higher temp and have negligable forces btn molecules.
- Because ideal gases do not exert force on each other, gases at high temperatures behave more ideally than gases under cooler temperatures
GENERALY, a gas behaves more ideally at high temp and lower pressure
ideal gas assumptions
Molecules of an ideal gas do not attract or repel each other.
Molecules of an ideal gas occupy zero volume.
Kinetic molecular theory
If an ideal gas is located in a container and temperature is increased, the average speed of the molecules will always increase.
What are network solids
are covalently bonded substances that do not include individual molecules. Instead they consist of atoms joined to form molecules that attract each other
through intermolecular forces.
- a substance is one large molecule
network solids also called macromolecular substances.
example: diamond and quartz (silicon dioxide), and they are hard to melt.
what is the heat of fusion
the amount of heat needed to move from solid to liquid past it’s melting point
The golden rule of phase change
Adding heat to a substance can change kinetic
energy or potential energy, but never both
Phase change and pressure rule and it’s EXCEPTION
when we increase pressure of the a liquid or gas, it makes it hard to boil or melt. However, if we lower the pressure, the boiling and melting point decreases.
Except: water, increasing pressure on water lowers the boiling or melting point and it’s apparent due to skating.
Explain how boiling occurs using pressure
As the pressure of the liquid increases, due to the influence of intermolecular forces, temperature, and molecular weight, in an open container, and the vapor pressure above the liquid becomes all vapor pressure, or it is equal to the atmospheric pressure, boiling occurs.
The relationship btn phase change and a substance’s average kinetic energy and intermolecular forces
- Solid: intermolecular forces»_space; kinetic energy of its molecules. So, molecules a re restricted in their ability to move.
- Liquid: intermolecular forces > kinetic energy of molecules, but this is enough to allow molecules to pass each other
- Gases: kinetic energy > intermolecular forces.
What happens when you boil water
Adding heat to water increases the kinetic energy of the molecules. At the boiling point molecules have become energetic enough to overcome the intermolecular forces btn water molecules
N.B: notice that changes of state involve intermolecular forces and not covalent bonds
Factors affecting vapour pressure
- intermolecular forces: for ex, gasoline is more volatile than water, b/c it has weak intermolecular forces, which increases it’s vapor pressure
- temperature: high temp increases av. kinetic energy of the molecules
- molecular weight.
Potential energy of solids compared to that of gases
Solid has the lowest In potential energy, b/c gases absorb heat to change from solid to gas.
Diff Gay-Lussac’s law, Boyle’s law, and Charles’ law.
Gay-Lussac: the volume is constant
Boyle’s: the temp is constant
Chales: pressure is constant
The equation showing the relationship btn a gas (derived from the ideal gas law euq)
MM = (dRT/P)
Why doesn’t all the particles in a gas have the same velocity at a given temperature
B/c temp is the measure of average kinetic energy or velocity. It is evident on the Maxwell-Boltzman diagrams
