Temperature and Its Measurement · 8 min read
Heat and temperature
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Introduction to heat and temperature
Many people think heat and temperature are the same thing, but in Physics, they are different. Imagine you are boiling a small cup of water and a big pot of water on the same gas cooker. Even if they both reach the boiling point, the big pot took more energy to get there. That energy is heat, while the boiling point is the temperature.
Understanding heat
Heat is a form of energy that flows from a hot place to a cold place. When you touch a cold bottle of minerals, heat leaves your hand and enters the bottle, which is why your hand feels cold. The SI unit of heat is the Joule (J).
Simply put, heat is the total energy moving because one thing is hotter than another.
Understanding temperature
Temperature tells us how hot or cold an object is. If you have malaria and your body feels hot, the doctor uses a thermometer to check your temperature. It does not tell us the total energy, only the level of 'hotness'. The SI unit of temperature is the Kelvin (K), though we use Celsius in Nigeria daily.
In simple terms, temperature is just a number that tells us how hot something is at that moment.
Difference between heat and temperature
There are three main differences to remember for your exams:
Heat is energy, while temperature is the state of a substance.
Heat is measured in Joules (J), while temperature is measured in Kelvin (K) or Celsius.
Heat depends on the mass and type of material, but temperature does not depend on the amount of matter.
For example, a small spoonful of boiling water and a whole bucket of boiling water have the same temperature (100 degrees Celsius), but the bucket has more heat because there is more water in it.
Calculations involving heat change
When we add heat to a substance, its temperature rises. We use the formula: H = mc(T2 - T1), where 'm' is mass, 'c' is specific heat capacity, and 'T' is temperature.
Example calculation
Calculate the heat required to raise the temperature of 2 kg of water from 30 degrees Celsius to 80 degrees Celsius. (Specific heat capacity of water = 4200 J kg-1 K-1).
1. Write down the values: m = 2 kg, c = 4200, T1 = 30, T2 = 80.
2. Find the change in temperature: 80 - 30 = 50 degrees.
3. Apply the formula: Heat (H) = 2 x 4200 x 50.
4. Final answer: H = 420,000 Joules (or 4.2 x 105 J).
Key points
- •Heat is energy in transit due to temperature difference.
- •Temperature is the degree of hotness or coldness of a body.
- •The SI unit of heat is the Joule (J).
- •The SI unit of temperature is the Kelvin (K).
- •Heat depends on mass, but temperature does not.