Temperature and Heat Energy

Temperature

• Heat is a form of energy that is used in various ways in daily life, including keeping us warm in winters and cooking food.
• Heat causes hotness or coldness in an object, and temperature is a measure of this hotness or coldness.

Effects of Heat

• When heat is given to an object, its temperature rises, making it hot.
• When heat is removed from an object, its temperature decreases, making it cold.

Measuring Temperature

• The sense of touch is not reliable for measuring temperature.
• A thermometer is a device used to measure the temperature of an object accurately.

Thermometer

• A thermometer is a long cylindrical tube with a scale and mercury inside.
• When a thermometer comes into contact with an object, the mercury expands and rises to a point on the scale, indicating the temperature of the object.

Temperature Scales

• There are three major types of temperature scales: degree Fahrenheit (°F), degree Celsius (°C), and Kelvin scale (K).
• Degree Celsius and degree Fahrenheit scales are commonly used, while the Kelvin scale is used in scientific work.

Celsius Scale

• The degree Celsius scale was developed by Anders Celsius.
• The lower fixed point is 0 °C (freezing point of pure water), and the upper fixed point is 100 °C (boiling point of pure water).
• The scale is divided into 100 equal divisions, with each division called one degree Celsius (°C).
• The normal human body temperature is 37 °C.

Fahrenheit Scale

• The Fahrenheit scale was invented by Daniel Gabriel Fahrenheit.
• The lower fixed point is 32 °F (freezing point of pure water), and the upper fixed point is 212 °F (boiling point of pure water).
• The scale is divided into 180 equal divisions, with each division called one degree Fahrenheit (°F).

Types of Thermometers

• There are three main types of thermometers: clinical thermometer, laboratory thermometer, and digital thermometer

Progress Check

• No specific notes required for this section

Kelvin Scale

• The Kelvin scale was proposed by William Thomson (Lord Kelvin) in 1848
• On the Kelvin scale, 273.15 K is the freezing point of water and 373.15 K is the boiling point of water
• There are 100 divisions between the freezing point and boiling point of water on the Kelvin scale
• Each division on the Kelvin scale is equal to 1 Kelvin (K), which is the SI unit for measuring temperature
• The formula to convert between temperature scales is: TC=TF−32180=TK−273.15100T_C = \frac{T_F - 32}{180} = \frac{T_K - 273.15}{100}TC​=180TF​−32​=100TK​−273.15​
• The formula can be used to convert between Celsius, Fahrenheit, and Kelvin scales
• Examples of temperature conversions:
  • Normal human body temperature (37 °C) is equivalent to 98.6°F
  • 50 °C is equivalent to 323.15 K