Heat and Temperature

Heat and Temperature Overview

01: History

  • Sir Benjamin Thompson (Count Rumford)

    • Lived: March 26, 1753 - August 21, 1814

    • Contribution: Challenged the caloric theory, proving heat is a form of energy.

  • James Prescott Joule

    • Lived: December 24, 1818 - October 11, 1889

    • Established that heat is energy.

02: What is Heat & Temperature?

  • Heat:

    • Definition: A form of energy that flows from higher temperature objects to lower temperature objects.

    • Transfer Process: Occurs through conduction, convection, and radiation.

    • Example: The sun radiates heat, warming the Earth.

  • Temperature:

    • Definition: The thermal state of a body controlling heat flow.

    • Determines direction of heat flow.

03: Source of Heat & Temperature

  • Natural Source:

    • The Sun:

      • 30% of sunlight is reflected back into space; 70% warms the Earth.

    • Other Natural Sources: Biomass, Tide.

  • Artificial Sources:

    • Heat generated through chemical reactions (burning fuels like coal, kerosene, wood, gasoline).

04: Types of Temperature Scales

  1. Celsius Scale

    • Water boils at 100°C, water freezes at 0°C.

  2. Fahrenheit Scale

    • Water boils at 212°F, water freezes at 32°F.

    • Commonly used in the US and some other regions.

  3. Kelvin Scale

    • Absolute temperature scale; water boils at 373.15K, freezes at 273.15K.

05: Celsius Scale

  • Anders Celsius

    • Devised the Celsius scale in 1741.

    • Commonly referred to as the centigrade scale.

    • Associated with water's properties.

06: Fahrenheit Scale

  • Daniel Gabriel Fahrenheit

    • Created the Fahrenheit scale, which is still widely used, particularly in the USA.

07: Kelvin Scale

  • Lord Kelvin

    • Named after Sir William Thomson.

    • Important in scientific contexts for absolute measurements.

08: Absolute Zero & Temperature Scale Comparisons

  • Absolute Zero:

    • Defined as 0 Kelvin (-273.15°C, -459.58°F).

    • Represents a state where atomic movement stops.

  • Temperature Comparisons:

    • Average space temperature around 2.7 K.

    • Human body averages around 37°C (310.15 K).

09: Types of Heat Transfer

  1. Conduction

    • Occurs in solids through direct contact.

    • Excellent transmitters of heat due to particle-to-particle transmission.

  2. Convection

    • Occurs in liquids and gases via moving currents.

    • Transfers heat through the movement of the substance itself.

  3. Radiation

    • Transfers heat through electromagnetic waves.

10: Relationship Between Heat and Temperature

  • Concept: Heat (q) is the thermal energy transferred from a hotter system to a cooler system.

  • Equation: Calculated using specific heat capacity (C), mass (m), and temperature change (∆T):

    • q = m x C x ∆T

11: Difference Between Heat and Temperature

  • Heat:

    1. Form of energy in motion.

    2. Causes a change in temperature.

    3. Flows from higher to lower temperatures.

    4. Measured in joules or calories.

  • Temperature:

    1. Degree of hotness or coldness of a body.

    2. Effect of heat.

    3. Determines the flow direction of heat.

    4. Measured in Celsius (°C), Fahrenheit (°F), or Kelvin (K).

12: Causes of Heat

  • Natural: Sunlight.

  • Artificial: Petroleum, natural gas, coal, and solar energy.

13: Causes of Temperature

  • Similar causes as heat: Sunlight, petroleum, natural gas, coal, and solar energy.

14: Results of Heat & Temperature

  • Heat and temperature relate as follows:

    • Heat (q): Thermal energy transferred.

    • Temperature: Average kinetic energy of atoms/molecules.

    • Calculated via the equation: q = m x C x ∆T.