p1.2.2 energy and temperature Flashcards
energy and temperature
what is temperature?
is a measure of the average kinetic energy of a substance particles, measured in degrees Celsius or kelvin
what is energy?
is the measure of the total thermal energy stored in an object measured in joules
what physical changes happen when a solid is heated?
particles gain more energy and they move more and their temperature increases
particles undergo a change of state e.g. melting or boiling
what chemical change happens when a solid is heated?
a reaction is triggered and different molecules are formed
what’s a physical change?
the change is reversible like changes of state e.g. filtering sand from water
what’s a chemical change?
the reaction is irreversible and a new substance is formed e.g. forming new salts
why is baking a cake a chemical reaction?
because you cannot change it to the way it was and the cake is now a new substance that has been foermed
why is melting chocolate a physical reaction?
because it can be returned to its former state by freezing and the particles undergoes a change of state e.g. melting
during a state change, what happens to the temperature of a substance?
it remains constant
why is energy being used in a state of change?
it is used to break (heating) or make (cooling) intermolecular bonds
cooling curve of steric acid
liquid
physical change
solid
what are factors that will affect the amount of heat required?
the type of material
the mass of material
the temperature
what is specific heat capacity?
the specific heat capacity of a material is the amount of heat required to raise the temperature of 1kg of a material by 1’c
what is the equation for change in thermal energy?
mass x specific heat capacity x temperature change
what is the equation for mass?
change in thermal energy / specific heat capacity x temperature change
what is the equation for temperature change?
thermal energy / specific heat capacity x mass
what is the equation for specific heat capacity?
change in energy / mass x temperature change
what is the unit for thermal energy?
j- joules
what is the unit for mass?
kg- kilograms
what is the unit for specific heat capacity?
j, ‘c, KJ-kilojoules
what is the unit for temperature change?
‘c
exam question-
water has a specific heat capacity of 4200 j/kg/’c 2kg of water is to be heated by 20’c calculate the energy required
16800j
what happens when a hot object and a cold object are left in a room?
hot objects get colder and cold objects get warmer until they reach thermal equilibrium- same temperature
what is specific latent heat?
the amount of energy required to change the state of 1 kg of material without a change in the temperature
what is the equation for thermal energy for a change of state?
mass x specific latent heat
what is the equation for mass?
energy / specific latent heat
what is the equation for specific latent heat?
energy/ mass
what is thermal energy for a change of state used for?
to break intermolecular forces between the atoms
what’s the difference between specific heat of melting and specific latent heat of boiling?
specific latent heat of melting applies to the energy required to melt 1kg of a material and of boiling applies to energy required to boil 1kg of a material
explain why the pressure of a balloon increases when more particles are blown into
gas pressure is caused when a gas particle collides with a surface and exerts a force onto it increasing the number of collisions on the balloons surface which increases the pressure and makes the balloon expands
what type of energy do gas particles get more of when heated?
thermal and kinetic
what is pressure?
pressure is the force per unit area it is measured in pascals
what would happen if pressure was reduced to zero?
the temperature reaches a minimum
what is the coldest possible temperature?
absolute zero
what happens when the temperature is absolute zero?
the particles have no internal energy and do not move
