KPM + TPM Flashcards
define the kinetic model of matter
matter is made up of tiny particles in random, continuous motion
define brownian motion
the random motion of tiny particles suspended in a fluid
why is the volume of a substance in solid state less than in liquid state
the particles in a solid are packed more closely together than in liquid state where particles are further apart. for the same number of particles, there is a smaller distance between them, hence solids have a smaller volume
why do gases have no fixed shape and size
the spaces between molecules are very wide, intermolecular forces of attraction are very weak
how do gas molecules cause pressure on a surface
gas molecules are in random, continuous motion. they occasionally collide with the walls of the surface, exerting force on it. the average force being exerted on the surface per unit area is pressure
why does an increase in temperature cause an increase in gas pressure
as temp increases, average kinetic energy of molecules increases. molecules collide with the walls of the container more frequently and with more force → larger force per unit area → higher pressure
pressure is DIRECTLY proportional to temperature when volume is constant
why does an increase in volume cause a decrease in gas pressure
when volume increases, the number of gas molecules per unit volume decreases. gas molecules collide with the walls of the container less frequently → average force exerted per unit area decreases → pressure decreases
pressure is INVERSELY PROPORTIONAL to volume when temperature is kept constant
why does an increase in temperature cause an increase in gas volume
when temperature increases, the average kinetic energy of gas molecules increases, and gas molecules collide more frequently with the walls of the container. in order to maintain a constant pressure, the volume of the gas must increase until it matches the pressure of the surrounding medium
volume is DIRECTLY PROPORTIONAL to temperature when pressure is constant
KPM formula
P1V1 = P2V2
define internal energy
the sum of the kinetic energy and potential energy of the particles in a system
the total kinetic energy associated with the random motion of particles and the total potential energy between the particles in the system
factors affecting kinetic energy
temperature of particles
factors affecting potential energy
forces between particles
distance between particles
due to intermolecular bonds
define heat capacity
the change in an object’s internal energy per unit change in its temperature
units of measurement for heat capacity
JK-1 or JºC-1
define specific heat capacity
the change in a material’s internal energy per unit mass for each unit change in its temperature
units of measurement for specific heat capacity
Jkg-1K-1 or Jkg-1ºC-1
formula for heat capacity
Q = mc delta theta
types of state changes
freezing
melting
evaporation
condensation
boiling
boiling vs evaporation
fixed temp vs any temp
throughout liquid vs surface of liquid
faster vs slower
heat source required vs not required
liquid temperature remains constant vs tends to fall
why is evaporation a cooling process
energetic molecules escape, while less energetic molecules are left behind. since they have a lower kinetic energy, the temperature decreases
factors affecting rate of evaporation
humidity
temperature
pressure
surface area
define latent heat
the energy released or absorbed to change the state of a substance at constant temperature
define specific latent heat of fusion
the amount of energy transferred to change a substance between solid and liquid state at constant temperature
define specific latent heat of vapourisation
the amount of energy transferred to change a substance between liquid and gaseous state at constant temperature
