Temperature and Thermometers Do Now Copy and Complete

Temperature and Thermometers

Do Now – Copy and Complete the table Evaporation and Condensation. flv Evaporation Change of state Where Temperature Boiling

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. 0 OC Freezing point of water lower fixed point 100 OC 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. 0 OC Freezing point of water lower fixed point 100 OC boiling point of water upper fixed point At normal atmospheric pressure – warm tea in an aircraft.

Temperature TEMPERATURE 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 HOT COLD until the two bodies reach thermal equilibrium – the same temperature

Thermal equilibrium Two bodies in thermal contact will eventually reach the same temperature. The two bodies are now said to be in thermal equilibrium. WARM

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 thermometer Place 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 thermometer Then place the tube in boiling water and label the new length as 100°C the upper fixed point 100°C

Making a Celcius thermometer Finally the range from 0 to 100 is subdivided into equal intervals. 100°C

Task Making a thermometer answer the questions

Temperature and Thermometers Common thermometers used today include the liquid-inglass 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 -200 o. C to 1100 o. C • 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 -10 o. C to 110 o. C

Measuring temperature • The thermometer has to be placed in thermal contact with whatever is being measured until 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 -200 o. C to 1100 o. C • Alcohol thermometer -10 o. C to 110 o. C for the school thermometers but can measure lower temperatures. • Mercury high temp of 500 o. C Linearity – 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 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/gasproperties_en. jnlp