temperature and thermometers
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Temperature and Thermometers
Do Now – Copy and Complete the table
Evaporation and Condensation.flv
Evaporation Boiling
Change of state
Where
Temperature
Learning today
• What is a thermometer scale • What Lower and Upper fixed points are• Thermal equilibrium• Different types of thermometer
What is Temperature?
Measuring Temperature
In 1742, Andreas Celcius created the temperature scale that is known by his name.
I’ve never heard of the Andreas scale, it must be a European thing
Celsius Scale
In the Celsius scale, a value of zero degrees is assigned to the freezing point of water, and a value of one hundred degrees to the boiling point of water.
0OC Freezing point of water lower fixed point 100OC boiling point of water upper fixed point At normal atmospheric pressure
Celsius Scale
A temperature scale is a measure of the level of hotness. Everyday temperatures are measured on the Celsius scale.
0OC Freezing point of water lower fixed point 100OC boiling point of water upper fixed point At normal atmospheric pressure – warm tea in an
aircraft.
TemperatureTEMPERATURE determines the direction of flow of thermal (heat ) energy between two bodies in thermal contact
Heat flows from where its hot to where its not
until the two bodies reach thermal equilibrium – the same temperature
HOT COLD
Thermal equilibriumTwo bodies in thermal contact will eventually reach the same temperature. The two bodies are now said to be in thermal equilibrium.
WARM WARM
Temperature
Temperature is also a measure of the average random kinetic energy of the particles in a substance.
Note that they are not all travelling at the same speed.
Temperature
The hotter the temperature, the faster the average speed of the particles
Note that they are not all travelling at the same speed.
Do Task
Finish questions 1-3 page 101
Read about the Kelvin scale
Making a Celcius thermometerPlace a glass tube containing mercury in a mixture of ice and water and labelling the position of the mercury as zero.
0°C
Making a Celcius thermometerThen place the tube in boiling water and label the new length as 100°C the upper fixed point
0°C
100°C
Making a Celcius thermometerFinally the range from 0 to 100 is subdivided into equal intervals.
0°C
100°C
Task
Making a thermometer
answer the questions
Temperature and ThermometersCommon thermometers used today include the liquid-in-glass type and the bimetallic strip and thermocouples.
Task
Make notes on liquid in glass thermometer
and a thermocouple
Thermocouple Thermometer
• Two different metals are joined to form two junctions.
• A temperature difference causes a tiny voltage which makes a current flow.
Thermocouples are • quick to respond to
temperature changes • a wide range -200oC to 1100oC • can be connected to computers
Liquid in glass thermometer
• Nearly all liquids expand slightly when heated.
• Thermometers use alcohol or mercury
• Mercury is toxic hence no longer used in schools
• School alcohol thermometers measure between -10oC to 110oC
Measuring temperature
• The thermometer has to be placed in thermal contact with whatever is being measured until the thermometer and object are in thermal equilibrium.
Stick in your books Thermometer Terms
Sensitivity – Some thermometers are more sensitive, the thread of liquid moves further. The narrower the tube the higher the sensitivity.Range • Thermocouple -200oC to 1100oC• Alcohol thermometer -10oC to 110oC for the school
thermometers but can measure lower temperatures. • Mercury high temp of 500oCLinearity – alcohol and mercury thermometers agree at the fixed points but not those in between as they have different expansion characteristics.
Do questions 1&2 page 105 followed by a
Graph question.
Kelvin Temperature
• Lord Kelvin• 1824-1907
• Task Temperature sheet
Kelvin Temperature
Kelvin temperature is proportional to the average random kinetic energy of the particles in a substance.
Note that they are not all travelling at the same speed.
Absolute/Kelvin temperature and Celsius
T (in Kelvin) = T (in degrees Celcius) + 273
Just to mention for now that zero Kelvin is the lowest possible temperature.
Measuring temperature
• The thermometer has to be placed in thermal contact with whatever is being measured until the thermometer and object are in thermal equilibrium.
Kelvin Temperature
• Lord Kelvin• 1824-1907
• Task Temperature sheet
Kelvin Temperature
Kelvin temperature is proportional to the average random kinetic energy of the particles in a substance.
Note that they are not all travelling at the same speed.
Absolute/Kelvin temperature and Celsius
T (in Kelvin) = T (in degrees Celcius) + 273
Just to mention for now that zero Kelvin is the lowest possible temperature.
Do questions 1&2 page 103
Pressure and Temperature
• http://phet.colorado.edu/sims/ideal-gas/gas-properties_en.jnlp
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