p3,p5 - missing pages

p3 - internal energy and changes of state + density

• increasing temp increases pressure, as colliding gas particles creates pressure

• density of a irregular solid object experiment - place your solid in a eureka can with a measuring cylinder placed underneath the spout, the solid will displace water in the can and it will spill out into the measuring cylinder, measure the volume of water that has been displaced into the cylinder and measure the mass of the object beforehand using a mass balance, so you can calculate the density of the object using the equation - density = mass / volume

• mass = density x volume - put this in an equation triangle

• density of a regular solid experiment - measure mass using mass balance then measure length, width and height using a ruler, calculate volume using the appropriate equation for the solid

• internal energy is the amount of energy stored in particles in a system

• the energy is stored in potential stores (gravitational and elastic) and kinetic energy stores

• when a substance is heated, energy is transferred to the particles kinetic energy stores - this increases internal energy

• specific heat capacity = the amount of energy needed to change the temp of a 1kg of a substance by 1 degree - for water it is 4200J

• equation - change in thermal energy = mass x specific heat capacity x change in temp

• specific latent heat = is the amount of energy needed change the state of a substance

• specific latent heat formula = energy = mass x specific latent heat

• a change in state occurs if there is enough kinetic energy provided to the particles to break their bonds

• when state is changed (liquid to gas by evaporation), mass is conserved, it won’t get heavier or lighter

p5 - reaction times and momentum

• average reaction time is between 0.2s and 0.9s

• can be affected by tiredness, drugs and alcohol

• you can use time = change in velocity / acceleration to calculate reaction time when doing the ruler test - same method applies in biology

• you use the acceleration equation because acceleration due to gravity is constant

• momentum is a vector quantity

• momentum = mass x velocity

• in a closed system, momentum before an event = momentum after

• this is the conservation of momentum

• if the momentum before an event is zero, it will be zero after

• in an open system, external forces such as friction can act on the objects, adding or removing momentum

• 2 balls in snooker have the same mass, the red ball isn’t moving, therefore it has 0 momentum, when a white ball (which is moving with velocity, meaning it has a momentum) hits the red ball, it causes it move move, meaning it now also has a momentum

• the white ball continues to move, but at a smaller velocity, so the combined momentum if the 2 balls is equal