temperature and thermometers

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