As we've learned, different materials have different properties when it comes to heat. Some materials heat up quickly, while others take a long time to change temperature, even when the same amount of heat energy is added. This difference is related to a fundamental property called specific heat capacity.

Specific heat capacity (c) is defined as the amount of heat energy required to raise the temperature of 1 kilogram of a substance by 1 degree Celsius (or 1 Kelvin). The unit for specific heat capacity is Joules per kilogram per degree Celsius (J/kg°C) or Joules per kilogram per Kelvin (J/kg K).

● Materials with a high specific heat capacity require a lot of energy to change their temperature. They absorb a large amount of thermal energy without a large increase in temperature. Conversely, they release a large amount of energy when they cool down. Water, for example, has a very high specific heat capacity (approximately 4200 J/kg°C). This is why it takes a long time to boil water, but once hot, it also stays hot for a long time. This property of water is crucial for regulating Earth's climate and for biological processes.

● Materials with a low specific heat capacity require less energy to change their temperature. They absorb a small amount of thermal energy to show a significant temperature increase. Metals, on the other hand, generally have low specific heat capacities (e.g., copper is about 390 J/kg°C), which is why they heat up and cool down quickly.

The relationship between heat energy (Q), mass (m), specific heat capacity (c), and temperature change (ΔT) can be expressed by the formula:

Q = m * c * ΔT

Where:
● Q = Heat energy transferred (in Joules, J)
● m = Mass of the substance (in kilograms, kg)
● c = Specific heat capacity of the substance (in J/kg°C)
● ΔT = Change in temperature (final temperature - initial temperature, in degrees Celsius, °C)

How much heat energy is required to raise the temperature of 2 kg of water from 20°C to 100°C? (Specific heat capacity of water = 4200 J/kg°C)

Given: m = 2 kg c = 4200 J/kg°C ΔT = (100 - 20)°C = 80°C
Using the formula Q = m * c * ΔT: Q = 2 kg * 4200 J/kg°C * 80°C Q = 672,000 J
So, 672,000 Joules (or 672 kJ) of heat energy are required. This shows that a significant amount of energy is needed to heat water, even for a relatively small mass.

If 10,000 J of heat energy is supplied to:
1. 1 kg of iron (specific heat capacity = 450 J/kg°C)
2. 1 kg of water (specific heat capacity = 4200 J/kg°C)
Which will experience a greater temperature change?
For iron: ΔT = Q / (m * c) = 10,000 J / (1 kg * 450 J/kg°C) = 22.2°C
For water: ΔT = Q / (m * c) = 10,000 J / (1 kg * 4200 J/kg°C) = 2.38°C
As you can see, the iron's temperature increases by a much larger amount (22.2°C) compared to water (2.38°C) for the same amount of heat energy, due to its lower specific heat capacity. This explains why metal objects sitting in the sun get much hotter than a pool of water.

Activity: You can conduct an experiment to compare the temperature changes in different materials. For example, take equal masses (e.g., 200 grams) of water, sand, and cooking oil. Place each in a separate, identical beaker. Heat each substance with the same heat source (e.g., a Bunsen burner on a low flame, or a hot plate set to the same level) for the same amount of time (e.g., 5 minutes). Then, measure the final temperature of each. You will observe that the sand and oil will likely have a higher final temperature than the water, demonstrating their lower specific heat capacities. This explains why beaches (made of sand) get hot quickly during the day and cool down quickly at night, while the ocean's temperature changes much more slowly.