P6 Flashcards
Molecules and matter
Give the equation for density
density (kg/m^3) = mass (kg)/volume (m^3)
Describe how to find the density of a solid, regularly shaped object
- gather equipment
[] mass balance
[] ruler
[] object (metal cube) - place the object on the mass balance and record its mass
[] if displayed in grams, convert to kilograms - measure the object’s side lengths with a ruler and convert to metres before multiplying together to find the object’s volume
- divide the mass by the volume to find the object’s density in kg/m^3
Describe how to find the density of a solid, irregularly shaped object
2 methods
- method 1
[] gather equipment (eureka can, water, measuring cylinder, object, mass balance)
[] measure and record the object’s mass using the mass balance and convert to kilograms if necessary
[] fill the eureka can with water until just under the spout’s opening, and place the measuring cylinder underneath the spout of the eureka can (if needed, put the can on a flat surface to raise it so that its spout is just above the measuring cylinder’s opening)
[] gently place the object in the eureka can, being careful not to splash any water out of the can
[] wait for water to stop flowing into the measuring cylinder
[] read and record the volume of water displaced and collected (this is equal to the object’s volume)
[] use the equation mass/volume = density to calculate the object’s density
- method 2
[] same thing but without the eureka can - just record the original volume of water in the measuring cylinder (fill about halfway) then record the end reading when object is placed in and take away the final reading from the initial to get the object’s volume
NOTE: when reading from a measuring cylinder, use the MENISCUS at eye level
Describe how to find the density of a liquid
- using a mass balance, measure and record the mass of the empty measuring cylinder
- measure certain volume of liquid using the same measuring cylinder
[] record the volume measured out and convert to m^3 if needed - measure the mass of the liquid and the measuring cylinder together using the mass balance again
- take away the empty cylinder’s mass from the total mass, then convert mass to kilograms if needed
- use density = mass(kg)/volume(m^3) to find the liquid’s density
What is the law of conservation of mass ?
mass cannot be created nor destroyed
- this is why a substance has the same mass regardless of what state it is in
Describe the kinetic theory of matter in relation to the three main states of matter
- solids
[] particles are held together in fixed positions and have very little KINETIC energy, so only vibrate in place - liquids
[] particles are not in fixed positions and have enough KINETIC energy to move around, but not enough to separate so the particles still touch - gases
[] particles have the most KINETIC energy and do not touch, instead moving rapidly and randomly
What is latent heat ?
- two types: latent heat of fusion and latent heat of vaporisation
- in general, latent heat is the heat energy transferred to a substance whilst it changes state, used to form or break bonds
[] the overall temperature does not raise or lower during this process, remaining constant at the melting/boiling points - latent heat of fusion = at melting/freezing point
- latent heat of vaporisation = at boiling/condensing point
What is the difference between boiling and evaporation ?
- evaporation = only at the surface of the liquid
- boiling = throughout the liquid
What is internal energy (definition + equation) ?
- internal energy is the total energy stored by the substance’s particles
- internal energy = potential energy + kinetic energy
[] potential energy = energy due to a particle’s position (in terms of states of matter)
[] kinetic energy = energy due to the INDIVIDUAL particle’s motion - NOT whole substance’s overall kinetic energy due to the entire substance moving
Describe a change in a substance’s state from solid to liquid to gas when heated (in terms of internal energy)
- solid
[] with heat, internal energy increases due to a rise in kinetic energy (heat energy converted to kinetic)
[] when melts, potential energy of the substance increases - at this point, particles have enough energy to break away from some of the intermolecular forces, but are still strong enough to keep the particles touching - liquid
[] with heat, internal energy increases due to a rise in kinetic energy (heat energy converted to kinetic)
[] when boils, potential energy of the substance increases and particles break away from their intermolecular forces almost entirely - gas
[] most internal energy
[] as heated, kinetic energy of the gas increases
[] frequency of collisions with the container and each other increase due to the increase in energy, and so the gas’ pressure increases also
Give the equation for the specific latent heat of fusion
SLHoF (J/kg) = energy supplied (J)/mass (kg)
Give the equation for the specific latent heat of vaporisation
SLHoV (J/kg) = energy supplied (J)/mass (kg)
What is specific latent heat ?
the amount of energy needed to change the state of 1kg of a substance
What is pressure of a gas caused by ?
- frequency of collisions between the gas particles and the surface of the container
- force of collisions between the gas particles and the surface of the container
[] angle of collision AND kinetic energy
Explain Brownian motion
- random motion of tiny particles in a fluid
[] helped advance the kinetic theory of matter by showing that particles moved randomly - first observed when botanist Brown observed pollen particles moving erratically and randomly floating on water
Describe how to observe the random movement of gas particles
- equipment
[] smoke cell
[] microscope
[] smoke - small glass cell filled with smoke
- light shone through the glass cell
- smoke particles observed with a microscope
[] constantly move and change direction randomly, carried by the random motion of the air it’s suspended in
What is Boyle’s Law (equation + explanation) ?
- pressure (Pa) x volume (m^3) = constant
- FOR A FIXED MASS OF GAS AT CONSTANT TEMPERATURE:
[] dec. volume = inc. pressure because increases density of the particles and thus likelihood of collision, so increases frequency of collision and thus pressure
Why does the temperature of a gas increase if compressed quickly in a piston ?
- to compress the gas, work has to be done on the piston
- this energy transfers to the gas
- if happens too quickly, the energy transfers to the gas faster than it can be dissipated and so raises the thermal energy of the gas
- if happens more slowly, energy can dissipate at the same rate it is transferred and so net temperature remains constant
