States of Matter Flashcards
kinetic energy
energy of motion. related to both mass and speed of particles.
temperature
a measure of average kinetic energy of particles.
relationship between temperature and kinetic energy
directly proportional relationship
as the temperature of a substance increases, the average speed/motion of its particles increases (since the mass of its particles does not increase).
standard temperature
0C = 273K
standard ambience temperature
25C = 298K
potential energy
stored energy that can be released at some point in time. in chemistry, potential energy is often referred to as enthalpy (H).
in terms of measuring chemical potential energy
enthalpy change
total chemical potential energy of substances cannot be measured directly, however, a change in enthalpy (∆H) for a given system can be determined by measuring temperature changes/ heat exchanges with its surroundings.
endothermic changes
a process that absorbs energy from its surroundings and increases the potential energy of the system is called endothermic. Hence, potential energy (of the system) experiences a positive change (+∆H) and the heat energy (of the surroundings) experiences a negative change (-∆T).
* particles separate
* attractions broken
* stability decreases
examples of endothermic reactions (in terms of state changes of matter):
1) Melting (Solid → Liquid):
2) Vaporization (Liquid → Gas):
3) Sublimation (Solid → Gas):
exothermic changes
a process that releases energy to its surroundings and decreases the potential energy of the system is called exothermic. Hence, potential energy (of the system) experiences a negative change (-∆H) and the heat energy (of the surroundings) experiences a positive change (+∆T).
* particles come together
* attractions formed
* stability increases
examples of exothermic reactions (in terms of state changes of matter):
1) Freezing (Liquid → Solid):
2) Condensation (Gas → Liquid):
3) Deposition (Gas → Solid):
changes of state/ phase changes
solid –>(melting)–> liquid –>(freezing)–> solid
liquid –>(vaporization)–> gas –>(condensation)–> liquid
solid –>(sublimation)–> gas –>(deposition)–> solid
states/phases of matter in order of increasing potential energy
1) solid (most potential energy): the molecules that make up a solid are arranged in regaular, repeating patterns. they are held firmly in place but can vibrate within a limited area.
2) liquid: the molecules that make up a liquid flow easily around one another. they are kept from flying apart by attractive forces between them. liquids assume the shape of their containers.
3) gas (least potential energy - ignoring plasma): the molecules that make up a gas fly in all directions at great speeds. they are so far apart that the attractive forces between them are insignificant.
gas pressure
the force from all of the combined collisions of the gas particles with a surface / the surface of its container. any change that causes more collision frequency o rgreater collision energy with the walls of teh contained will cause an increase in pressure (and vice versa for a decrease in pressure).
atmospheric pressure
normal atmospheric pressure at sea level is called standard pressure.
standard pressure = 1.0 x 10^5 Pa = 100 kPa
- KiloPascals (kPa) will be the most useful unit of pressure for the IB exam
- when questions describe changes in pressure, they are generally describing changes to the external pressure around a sample of gas.
directly proportional relationships
(linear) means that a change in one quantity causes a change by the same factor, in the same direction, in another quantity. When quantity X doubles quantity Y doubles, when quantity X halves quantity Y halves, etc.
inversly proportional relationship
(not linear) means that a change in one quantity casues a change by the same factor in the opposite direction in another quantity. When quantity X doubles quantity Y halves, when quantity X halves quantity Y doubles, etc.
gas laws
relationship between pressure and volume for a gas
inversly proportional, thus if pressure increases, volume decrease, and vice versa.
P1V1 = P2V2
gas laws
relationship between temperature and volume for a gas
directly proportional, as temperature increases so does the volume of the gas. V1/T1 = V2/T2
gas laws
relationship between temperature and pressure for a gas
directly proportional, as temperature increases so does pressure. P1/T1 = P2/T2
gas laws
relationship between volume and moles of a gas
directionally proportional, as volume increases so does moles. V1/n1 = V2/n2
important consideration of Avogadro’s Law: equal volumes of gas contain equal moles of gas particles ( under teh same conditions). therefore 1 mole of any gas (under the same conditions) should occupy the same amount of volume. while the mass may change, the number of particles stays the same.
assumptions about ideal gases (what an ideal gas consists of)
(those in bold are the faultiest assumptions)
1) gas particles move in straight line motion
2) gas particles experiences no attractions for other gas particles. (no intermolecular forces). This leads all collisions being considered elastic (no energy loss).
3) gas particles’ average kinetic energy (speed) is proportional to their absolute temperature (in Kelvins)
4) gas particles themselves takes up negligible volume when compared to the overall volume of the gas.
(not an assumption) gases are mostly empty space. the particles have a lot of empty space between them. this allows them to compressed into smaller volumes
when do real gases deviate from the ideal gas model?
Low Temperature: Particles move slowly, and intermolecular attractions become significant.
High Pressure: Particles are closer together, making the volume of the particles NOT be negligible anymore
High Density (Small Volume): The volume of particles is no longer negligible compared to the total volume.
Why are the units of Kelvin necessary?
Because there is no negative temperature, it is NOT possible to have negative kinetic energy
molar volume
22.7 dm^3
At STP, 1 mole of an ideal gas occupies 22.7 dm³
when are gases most likely to act like ideal gases?
high temps and low pressure is when gasses are most likely to act like ideal gases
STP
STP stands for Standard Temperature and Pressure
Temperature: 273K (0∘C)
Pressure: 100kPa
At STP, 1 mole of an ideal gas occupies 22.7 dm³
SATP
SATP stands for Standard Ambient Temperature and Pressure
Temperature: 298 K (25 C)
Pressure: 100kPa
describe the behaviour of particles in the solid, liquid and gas phase based on the kinetic molecular theory.
solid - vibrating in fixed positions
liquid - held near each other, moving past each other. No fixed positions.
gas - far apart from each other, moving in straight line motion.
