Difference Between Heat and Temperature in Thermal Physics

In thermal physics, heat and temperature are important ideas that explain different parts of thermal energy. Knowing these concepts is very important for students in Year 1 Physics.

What They Mean

1. Heat:

   • Heat is a kind of energy that moves between things or objects because of a difference in temperature.
   • It travels from something hot to something cold until they are the same temperature.
   • We measure heat in joules (J) in the International System of Units (SI). Other units like calories (cal) and British thermal units (BTU) are also used.
   • For reference, 1 calorie is about 4.184 joules, and 1 BTU is about 252 calories.

2. Temperature:

   • Temperature tells us how hot or cold something is, based on the average movement of the tiny particles in a material.
   • The SI unit for temperature is Kelvin (K), but we often use degrees Celsius (°C) and Fahrenheit (°F) too.
   • Here are the formulas that connect these units:
     • $T(K) = t(°C) + 273.15$
     • $T(°F) = \frac{9}{5}t(°C) + 32$

Main Differences

• Nature:

  • Heat is energy that is moving, while temperature tells us the energy state of something.

• Properties:

  • Heat depends on the mass and specific heat capacity of a substance, which means it can change with different amounts of material.
  • Temperature does not depend on how much material there is. For example, a small amount of water at 100 °C is the same temperature as a large amount of water at that temperature.

• Measurement:

  • We measure heat using a method called calorimetry.
  • We measure temperature with thermometers, which can be mercury, digital, or infrared thermometers.

The Math Behind It

The link between heat transfer ($Q$) and temperature change is shown by this equation:

$$Q = mc\Delta T$$

where:

• $Q$ = heat energy transferred (in joules)
• $m$ = mass of the substance (in kilograms)
• $c$ = specific heat capacity of the substance (in J/kg·K)
• $\Delta T$ = change in temperature (in K or °C)

This formula explains that the heat transferred to or from something depends on its mass, the specific heat capacity, and the temperature change.

Real-Life Examples

1. Heating Water:

   • If you heat 2 kg of water (with a specific heat capacity of $c \approx 4,186 \text{ J/(kg·K)}$) and raise its temperature from 20 °C to 100 °C, the heat absorbed can be calculated like this:
   $$Q = mc\Delta T = 2 \text{ kg} \times 4,186 \text{ J/(kg·K)} \times (100 °C - 20 °C) = 66,976 \text{ J}$$

2. Cooling a Metal Rod:

   • When you cool a metal rod, it releases heat energy to the air, and the temperature of the rod goes down.

Conclusion

To wrap it up, heat and temperature are related ideas in thermal physics, but they have different roles. Heat is the energy moving between things, while temperature measures how that energy affects the motion of particles. Knowing these differences is important for understanding the basics of thermal physics in Year 1 Physics.