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Do Now. Write down three thing you need to do to work safely in a science laboratory. Outcomes: Understand that different materials require different amounts of energy to increase their temperature. Know the equation. Be able to use the equation. - PowerPoint PPT Presentation
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© Boardworks Ltd 20061 of 32
© Boardworks Ltd 20062 of 32
Do Now
•Write down three thing you need to do to work safely in a science laboratory
© Boardworks Ltd 20063 of 32
SPECIFIC HEAT CAPACITY
Outcomes:•Understand that different materials require different amounts of energy to increase their temperature.•Know the equation.•Be able to use the equation.•Be able to describe an experiment to measure heat capacity.
© Boardworks Ltd 20064 of 32
Copy this Glossary
absorber – A material that takes in thermal radiation.
conduction – The method of heat transfer in solids.
conductor – A material that lets heat flow through it.
convection – The method of heat transfer in fluids, which occurs because hot fluids are less dense than cold fluids.
emitter – A material that gives out thermal radiation.
free electrons – Electrons in a metal that are free to move through the metal.
heat transfer – The flow of heat energy from a hotter area to a colder area.
radiation – Heat energy transferred by infrared waves. This method of heat transfer does not need particles.
© Boardworks Ltd 20065 of 32
How does energy affect materials?
Do different materials need the same amount of energy to increase their temperature by the same amount?
To increase the temperature of 1 kg of water by 1°C, requires 4200 J.
To increase the temperature of 1 kg of copper by 1°C, requires 390 J.
Water and copper require different amounts of energy because they have different values for a property called specific heat capacity.
and for copper is 390 J/kg°C.
It is the amount of energy required to increase the temperature of 1 kg of a material by 1°C.
So, the specific heat capacity for water is 4200 J/kg°C
© Boardworks Ltd 20066 of 32
What is specific heat capacity?
The specific heat capacity of a material is the amount of energy required to raise 1 kg of the material by 1 °C.
Energy is measured in joules (J).
It can be used to work out how much energy is needed to raise the temperature of a material by a certain amount:
energyspecific heat
capacitytemperature
change= mass x x
Mass is measured in kilograms (kg).
Temperature change is measured in °C.
Specific heat capacity is measured in J/kg/°C.
© Boardworks Ltd 20067 of 32
Calculations using S.H.C.
Energy absorbed = Mass x Specific Heat capacity x Temp rise
The Mr McT equation
E = mcΔT
J kg
J/kg/°C °C
© Boardworks Ltd 20068 of 32
For example
0.5 kg of olive oil is heated until its temperature rises by 120 K. If the specific heat capacity of olive oil is 1970 J/kg/°C, how much heat energy was used?
Energy absorbed = Mass x Specific Heat capacity x Temp rise
Energy absorbed = 0.5 x 1970 x 120
Energy absorbed = 118200 J
© Boardworks Ltd 20069 of 32
Practical
A
V12V
A metal
© Boardworks Ltd 200610 of 32
Go through Practical worksheet
Follow instructions.Take measurements and do calculations.
All students must complete the lab sheet
© Boardworks Ltd 200611 of 32
Measuring SHCs
• Energy put IN to metal = voltage x current x time• Energy = mass x specific heat capacity x temp
rise
voltage x current x time = mass x specific heat capacity x
temp rise
Specific heat capacity = (voltage x current x time)/(mass x temp rise)
© Boardworks Ltd 200612 of 32
Specific heat capacity example
Using the specific heat capacity of water (4200 J/kg°C), how much energy is needed to increase the temperature of 600 g of water by 80°C in a kettle?
energy = 0.6 x 4200 x 80
= 201 600 J
Note: mass = 600 g = 0.6 kg
energyspecific heat
capacitytemperature
change= mass x x
© Boardworks Ltd 200613 of 32
Do nowSpecific heat
questionsQ5 June 2005
Latent heat
Learning today • Use the terms latent heat of fusion
and give a molecular interpretation of latent heat
• Describe an experiment to measure specific latent heats for ice
• Test Sunday 1st April 2012• I will collect your books on
Monday
Latent Heat
Latent heat
In a change of state experiment, from the graph you will notice a flat spot the temperature of the salol stopped changing as the salol changed from a liquid to a solid.
Temp (°C)
Time (mins)
Melting point
Specific Latent heat “latent” = “hidden”
Why does
this happen?
Specific Latent heat - Copy When a substance changes from solid to liquid or from
liquid to gas, it takes energy to change its state. Heat is needed to break the bonds or separate the molecules. The temperature remains the same. When a liquid changes back to a solid energy is released again as the bonds form again.
solid to liquid increasing their potential energy instead of raising the temperature (kinetic energy
Temp (°C)
Time (mins)
Melting point
solid
liquid
Specific Latent heat - copy
The specific latent heat of a substance tells us how much energy is needed to change the state of 1 kg of substance at constant temperature.
Solid to liquid/liquid to solid
or
liquid to gas/gas to liquid
Specific Latent Heat
The specific latent heat of fusion (melting) of ice at 0 ºC, for example, is 330000 J.kg-1. This means that to convert 1 kg of ice at 0 ºC to 1 kg of water at 0 ºC,
330000 J of heat must be absorbed by the ice.
1 kg 1 kg
334000 J absorbed
All at 0°C
Specific Latent Heat
Conversely, when 1 kg of water at 0 ºC freezes to give 1 kg of ice at 0 ºC, 330000 J of heat will be released to the surroundings.
330000 J released
1 kg 1 kgAll at 0°C
Specific Latent Heat -Copy
Energy = mass x specific latent heat
J kg J/kg
E = mL
Specific Latent heat LE = m L
Do Now question 1 page 119
Learning today • Use the terms latent heat of fusion
and fusion and give a molecular interpretation of latent heat
• Describe an experiment to measure specific latent heats for ice and steam
•Test Sunday 1st April 2012• I will collect your books Today
Specific Latent Heat of Fusion Experiment
• Readings required • Energy supplied by heater• Energy = Power x time• Time = • Energy = VIt• Mass of water • E = mL
• Latent heat = Energy supplied . mass of water
Specific Latent Heat of Fusion Experiment • Energy = Power x time• Time =• Energy = VIt =
• Mass of water =
• E = mL• L = E /m• Latent heat = Energy supplied
. mass of water
Task- Evaluation
• What are the limitations in our method?• What solutions can you think of?• Why do we wait until the water is
dripping?• Does all the heat come from the heater?• Does all the ice remain in the funnel?• Now do Q4 Nov 2005
Markscheme4 (a) •turn on heater and wait until water starts dripping in beaker•empty beaker & replace, start watch•stop watch & remove beaker at same time•record time•find and record mass of water in beaker
(b) 60 x t = 120 x 340 t = 680 s
(c) (i) ice gains heat from surroundings/ice falls through funnel
(ii) lag or fit lid to funnel/place gauze in funnel bottom
Specific Latent Heat of Fusion Experiment
Latent heat
Now doNov 2005
Q5
Specific Latent Heat of Vaporisation - Copy
For water at its normal boiling point of 100 ºC, the latent specific latent heat of vaporisation is 2260000 J/kg. This means that to convert 1 kg of water at 100 ºC to 1 kg of steam at 100 ºC, 2260000 J of heat must be absorbed by
the water. vice verse for vapour to liquid
All at 100°C
2260000 J input
1 kg 1 kg
Specific Latent Heat of Vaporisation
Conversely, when 1 kg of steam at 100 ºC condenses to give 1 kg of water at 100 ºC, 2260 kJ of heat will be released to the surroundings.
All at 100°C
2260000 J released
1 kg 1 kg
Specific Latent Heat of Steam
Latent Heat
Specific Latent Heat -Copy
Energy = mass x specific latent heat
J kg J/kg
E = mL
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