Module 5 Specific Heat Capacity Flashcards
What is the arrangement and behaviour of particles in a solid?
Arranged in a regular pattern
Tightly packed
Atoms vibrate in their fixed (mean) positions
Explain what happens to the energies of particles in a solid when heated?
Atoms gain KE
Vibrate with higher speed and amplitude
PE remains constant (almost, small amount of expansion)
What happens to the particles at the melting point?
KE of atoms is constant (temp is constant)
Atoms gain PE as work done to increase separation
Describe the arrangement and behaviour of particles in a liquid
Atoms are free to move throughout structure
Packed tightly
Random arrangement
What happens to the energies of the particles when a liquid is heated?
gain KE and move with greater speed
What happens to the particle energy at the boiling point
KE of atoms is constant (temperature is constant)
Atoms gain PE as work done to increase separation greatly
Describe the arrangement and behaviour of particles in a gas
Atoms move randomly
With high KE
Large spacing between atoms
What is the definition of internal energy?
sum of random distributions of kinetic energies and potential energies of all atoms in a substance
What is the symbol of internal energy?
U
What are the two ways in which U can be altered?
Changing temp which changes KE
Change the state of matter which changes PE
Describe the energy changes that take place during melting
Change of state
Temp is constant so KE is constant
PE of molecules increase as work done to increase separation
Thus U rises
Describe the energy changes that take place during boiling
Change of state
Temp is constant so KE is constant
PE of molecules increase as work done to increase separation
Thus U rises
Describe the changes in energy as temp is increased for gases
Molecules gain KE so U rises
No PE for ideal gases
Define internal energy of an ideal gas
Sum of the random distribution of kinetic energies of the particles
(no potential energy for ideal gases)
What is specific heat capacity a measure of (not definition)?
how hard it is to change the temp of a substance
What does specific actually mean?
per unit mass or per kg
What does a high gradient of temp against time graph represent in terms of specific heat capacity?
easy to change temperature
(small change in time large change in temp) thus c is small
What is the definition for specific heat capacity?
specific heat capacity is the energy required to change the temperature of a unit mass by a unit temperature change
What is temperature in kelvin also known as?
absolute temperature
Why is water having a high heat capacity useful?
Can absorb or emit a lot of energy for a small temp change
Thus can be used in central heating
Cooling systems
Used in body to prevent fluctuations of temp due to metabolic reactions
When mixing substances, what can be assumed about the changes of energy?
Assuming no energy lost to surroundings,
energy lost by hotter object = energy gained by cooler object
What is eventually reached when two substances are mixed?
thermal equilibrium
Describe the measurements that must be taken to find the specific heat capacity of a metal using a circuit
Measure mass of object using electronic balance
Measure initial temperature using thermometer
Measure current (ammeter) and voltage (voltmeter)
Calculate the power supplied using measurements of I and V
Find the energy supplied by using P x t
Give the two examples of sources of error when finding c for a solid
Time taken for heat to conduct through object
Heat lost to surroundings
State, and explain how sources of error are avoided when finding c experimentally for a solid
Time taken for heat to conduct through block. Wait to record final highest temperature
Heat loss to surrounding — start the experiment at 10 degrees below room temp, then finish at 10 degrees above. Heat lost to and gained from surroundings will balance.
What are the sources of error for a liquid and state how they may be avoided
Liquids are poor conductors thus must be stirred for even distribution of heat
Time for heat to transfer through liquid, wait to record final and highest temp
Heat lost to container - find m, c and change in temp for container. Subtract this value of energy from the overall E=VIt
Define specific latent heat?
the energy required to change the state of a unit mass at constant temperature
What is L (in the thermodynamics topics)
specific latent heat
What is the unit for L?
J kg-1
What is the definition for Lf
Specific latent heat of fusion is
energy required to change a unit mass from solid to liquid at constant temperature
What is the definition for Lv
Specific latent heat of vaporisation is
energy required to change a unit mass from liquid to gas at constant temperature
What is the symbol for specific latent heat of fusion?
Lf, for solid to liquid (or liquid to solid)
What is the symbol for latent heat of vaporisation?
Lv, liquid to gas (or gas to liquid)
Describe how you find the Lf of ice
Set up an apparatus with a heater in to a funnel with ice and a thermometer over a beaker over an electronic balance
Once the thermometer reads zero, record initial mass and turn on heater for 5 minutes
Read ammeter and voltmeter readings
Turn power supply off and record the final mass of the balance
Find the change in mass then the energy supplied using E=IVt
Calculate Lf using E/m
Describe how you would find the Lv of water
Place a heater and thermometer into a flask of water which is suspended in a large condenser
Turn on heater and wait till thermometer measures 100ºC
Record ammeter and voltmeter readings and initial mass of collection flask
After five minutes switch off heater and wait for all gas to condense
Work out energy supplied using E=IVt then Lv using E/m where m is the change in mass
