Heat and Temperature
Heat is a form of energy. It travels from hot body to a cold body. While temperature is the measurement of how hot or cold a body is. These two things are not same but are closely related. Heat energy travels from a hotter body to a colder one, as an object gains heat energy, its temperature rises gradually. When heat energy moves out of an object or a body, the temperature of such body will fall. To calculate the temperature we use various thermometers.
Fahrenheit and Celsius Scale
Many scales have been devised over the decades, and almost all of them are forgotten. The Fahrenheit is an old scale still used today although the centigrade scale is more commonly used. But even the centigrade scale is not as recognized as the Celsius scale, because it has been devised by the Swedish scientist Anders Celsius in the eighteenth century. The centigrade and the Celsius scale have little difference. The scale for Fahrenheit is °F. The scale for Centigrade and Celsius is °C.
Making a thermometer Scale
A thermometer scale is made by calculating the boiling point and the melting point of a pure substance. A pure substance is essential for this because impurities in a substance alters the boiling point and the melting point of the substance. These impurities lowers the melting point and raise the boiling point.
For measuring the melting point of a substance, use ice cubes and put them in a funnel over a beaker and place a thermometer in between the cubes. As the ice starts to melt, it will gain heat. Read the temperature and mark this as the melting point of the pure substance.
To measure the boiling point, pour pure water in a flask and heat it over a Bunsen burner. Fix the thermometer above the water and not in the water. The water will gain heat energy and will turn into steam. Read the temperature and mark this as its boiling point.
The Centigrade and the Celsius scale are not scientifically used as these are unreliable. Some substances have a temperature below 0 and so have to be written as negative numbers. This makes it useless and so a new scale had been devised called the Kelvin, by the physicist Lord Kelvin. For devising the scale, the lowest melting point was taken in Centigrade/Celsius which is thought to be -273°C. This value is taken to be 0 K in the Kelvin scale. This scale is not written in degrees because it is an SI unit of temperature. To convert a Centigrade/Calvin Scale into Kelvin or Kelvin into Celsius/Centigrade scale is a matter of adding or subtracting 273 from the readings:
Celsius reading + 273 = Kelvin
Celsius = Kelvin – 273
Liquid In Glass Thermometer
The liquid in glass thermometer is most commonly used in clinics. The liquid in glass thermometer has a few properties which is very helpful for measuring temperature. The glass which makes the body of the capillary tube is thick acting as a magnifying glass for easy reading of the measurements. The bore was first made of glass but commonly is made of metal since metals are good conductors of heat. The liquid inside the glass is either alcohol (ethanol) or mercury. Both have their disadvantages and advantages but mercury is more commonly used as it reacts to heat better than alcohol.
Electronic thermometers are rising in popularity because of their ease of use. These thermometers show temperature digitally and has probes inside it which help do its function. The heat conducted by the metallic bore produces a resistance which forms the electrical energy needed for the thermometer to do its function. These thermometers are cheap and are easy to use and read temperature.
Thermocouple thermometers are not commonly used but are great to use for an electronic circuit and for measuring high temperatures. The thermometer has two wires made of different metals, both wires join at a junction out of the two junctions. The conduction produces a resistance which can be connected to an electrical device. The advantages for using this kind of thermometer is:
- It can measure huge amounts of temperature, such as 1800°C, depending on the metals used for wires.
- The thermometer can be used in an electronic circuit.
- The metals are good conductors which is why these are best suited for temperature measuring making thermocouple thermometer more responsive to temperature changes.
- The wire junctions can be made small to use it to measure in small spaces.
Thermochromic or Thermocolor thermometer is more simple to use and is used for household purposes, mainly to check the temperature of an ill person. The thermometer has liquid crystals in it which change color due to rise in temperature.
With this I end this article