TemperatureAndHeat_SP25

Temperature and Heat

Understanding Temperature

• Temperature refers to the measurement of heat.

• It is important to note that an object does not contain heat; rather, it possesses a certain energy content, and the energy exchanged between objects due to temperature differences is termed heat.

Useful Definitions

• Temperature: Measurement of heat.

• Heat (Q): A form of energy.

• Absolute Zero: The temperature at which all molecular motion ceases; -273.15°C.

Temperature Scales

• Fahrenheit:

  • Freezing: 32ºF

  • Boiling: 212ºF

• Celsius:

  • Freezing: 0ºC

  • Boiling: 100ºC

• Kelvin:

  • Freezing: 273.15K

  • Boiling: 373.15K

Relationships Between Scales

• Fahrenheit (°F), Celsius (°C), and Kelvin (K) have specific conversion formulas

  • Conversions include:

    • T°_F = (9/5) T°_C + 32

    • T°_C = (5/9) (T°_F - 32)

    • T_K = T°_C + 273.15

Absolute Zero

• Defines the point where all molecular motion ceases.

• At this temperature, the pressure of any gas would theoretically equal zero.

Conceptual Questions

• Does the temperature of a body depend on its size?

• When bricks A and B are placed in thermal contact, which brick had the higher initial temperature? (Heat flows from hot to cold)

Heat Transfer Concepts

• Heat Transfer: The movement of heat energy from one place or material to another.

• Conservation of Energy: Energy cannot be created or destroyed.

Laws of Thermodynamics

• Zeroth Law of Thermodynamics: If object A is in thermal equilibrium with object B, and object C is also in thermal equilibrium with B, then A and C will be in thermal equilibrium if brought into contact.

Measuring Heat and Heat Transfer

• Energy added to a system increases its energy in the form of heat.

• Calorie: The amount of energy needed to raise the temperature of 1g of water by 1ºC (1 Calorie = 1000 calories).

• 1kcal = 4186J.

Thermal Expansion

• Most substances expand when heated, with some exceptions (e.g., water).

• Examples: Power lines in summer vs. winter, hot air balloons, expansion joints in bridges.

• Linear Expansion Equation: ΔL = αL₀ΔT

• Volume Expansion Equation: ΔV = βV₀ΔT

Specific Heat and Heat Capacity

• Heat Capacity (C): The amount of heat needed for a given temperature change (C = Q/ΔT).

• Specific Heat (c): Varies by substance and is defined as the heat required to raise 1 kg of a substance by 1ºC (c = Q/(mΔT)).

• Water's Specific Heat: 4186 J/kg·K.

Example Calculations

1. Temperature conversion examples between Fahrenheit and Celsius, including sample rates of heat for specific materials.

2. Calculating how much heat is needed to raise the temperature of given quantities of water and metals under varying scenarios.