particle model of matter Flashcards
what is the definition of density? state the relevant equation with units
-the mass per unit volume of a material
-density = mass / volume
-density (kg/m^3), mass (kg), volume (m^3)
state the different states of matter in order (least to most) of density of atoms
-least dense: gas
-liquid
-most dense: solid
describe the particle arrangement of a solid
tightly packed in a regular arrangement. particles can only vibrate on the spot
describe the particle arrangement of a liquid
close together, but with an irregular arrangement. they can flow over each other
describe the particle arrangement of a gas
separated, with no regular arrangement. particles can move freely
what is always conserved when a substance undergoes a change of state?
mass
how does a change of state differ from a chemical change?
in a change of state, the material can return to having its previous properties if the change is reversed
what is sublimation?
when a solid changes into a gas without passing through a liquid state
what is evaporation?
when a liquid changes into a gas state
what is the opposite of evaporation?
condensation, which is when a gas changes into a liquid state
when water boils in an open pan, why does the mass of the pan of water appear to decrease?
some of the water will evaporate and turn into water vapour. this will leave the pan meaning the mass of the pan will decrease. the mass of the whole system however remains constant
explain the processes involved when a bathroom mirror mists up
-hot water evaporates to form water vapour
-this water vapour lands on the cooler mirror
-the vapour condenses and returns to liquid state on the mirror’s surface
what is the internal energy of a substance?
-the energy stored by the particles
-the sum of the total kinetic and potential energies that make up the system
how does heating affect the energy of a substance?
-heating transfers energy to the substance
-it increases the energy of the particles that make up the substance
what two things can heating a substance do?
-raise its temperature
-change the state of the substance
what three factors determine the temperature change of a system?
-mass of substance being heated
-type of material (specific heat capacity)
-energy inputted into the system
state the equation used to calculate the temperature change when a substance is heated. give appropriate units
energy = mass x specific heat capacity x temperature
energy (J), mass (kg), specific heat capacity (J/kg/C), temperature (C)
define specific heat capacity
the amount of energy needed to increase the temperature of 1kg of a substance by 1C
describe how the internal energy and temperature of a substance changes when a change of state occurs
-the internal energy of the substance will be increased or decreased
-the temperature of the substance will remain constant
define specific latent heat
the amount of energy needed to change the state of 1kg of a substance with no change in temperature
state the equation for the energy required to change state. give appropriate units
energy to change state = mass x specific latent heat
energy (J), mass (kg), specific latent heat (J/kg)
what is the specific latent heat of fusion?
the energy required to change 1kg of a substance from solid state to liquid state without a change in temperature
what is the specific latent heat of vaporisation?
the energy required to change 1kg of a substance from liquid state to gas state (vapour) without a change in temperature
describe the motion of molecules in a gas
they are in constant random motion
what factor affects the average kinetic energy of gas molecules?
-the temperature of the substance
-the higher the temperature, the higher the average kinetic energy of the molecules
what effect does increasing temperature have on the pressure of a gas when held at constant volume?
pressure of the gas will increase as the temperature increases
why does pressure increase as temperature increases (at a constant volume)?
-kinetic energy of molecules increases
-collisions between molecules becomes more frequent
-greater rate of change of momentum
-greater force and therefore pressure
if gas A is at a low pressure, and gas B is at a high pressure, what can be said about the rate of collisions in each gas?
-there are more collisions per second in gas B than in gas A
-the rate of collisions is higher in B
outline the basic steps of calculating the density of a regularly shaped object
-measure the dimensions of the regular shape and calculate the volume
-measure the mass of the shape using a calibrated balance
-calculate density from the mass and volume
give the formula for the volume of a prism
volume = area of face x height
what equation is used to calculate volume of a rectangular prism?
volume = length x width x height
(also applies to cubes)
give the formula for the volume of a sphere
volume = 4/3 x π x radius^3
V = 4/3 π r^3
what equation is used to calculate density?
density = mass / volume
what unit is used for density?
kg/m^3
what piece of equipment is used to measure the object’s mass? what must you do before using it?
a digital balance, which should be zeroed before placing the object on it to avoid a zero error
how do you convert from g/cm^3 to kg/m^3?
multiply the value by 1000
outline the basic steps of calculating the density of a irregularly shaped object
-measure the mass of the irregular shape
-fill a displacement can with water and submerge the object
-record the volume of water that has been displaced
-calculate the density from the mass and volume
what should you place under the can spout to collect the water?
a measuring beaker
explain how you should fill the displacement can to get the most accurate results
fill the can until water starts to drip out of the spout and into the beaker. wait until the dripping just stops before submerging the object
outline the basic steps of calculating the density of a liquid
-measure the mass of the empty measuring cylinder
-pour around 100cm^3 of liquid into the cylinder and record the volume
-measure the mass of the cylinder with liquid in, and subtract the cylinder’s mass to calculate the mass of liquid.
-calculate density from mass and volume
how does the density of solids and liquids compare?
in general, solids are more dense than liquids since their particles are more tightly packed together meaning there is more mass per unit volume
