## Specific Heat Capacity of Water
### Definition
Specific heat capacity, often denoted by the symbol (c), is a physical property that measures the amount of heat energy required to raise the temperature of a unit mass of a substance by one degree Celsius. It is expressed in units of joules per gram per degree Celsius (J/g⋅°C).
### Specific Heat Capacity of Water
Water has a high specific heat capacity compared to most other substances. The specific heat capacity of water is:
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c = 4.187 J/g⋅°C
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This means that it takes 4.187 joules of heat energy to raise the temperature of 1 gram of water by 1 degree Celsius.
### Significance of High Specific Heat Capacity
The high specific heat capacity of water is significant for several reasons:
– Temperature Regulation: Water’s high specific heat capacity helps regulate Earth’s temperature. Oceans and large bodies of water absorb and release heat slowly, mitigating extreme temperature fluctuations.
– Heating and Cooling: Water is commonly used in heating and cooling systems because it can absorb and release large amounts of heat without experiencing significant temperature changes.
– Biological Processes: The high specific heat capacity of water is essential for maintaining temperature stability in living organisms. It prevents rapid temperature fluctuations that could damage cells and tissues.
### Applications
The high specific heat capacity of water has various applications, including:
– Heat Storage: Water is used in heat storage systems, such as solar water heaters, to store thermal energy.
– Cooling Systems: Water is widely used as a coolant in engines, air conditioners, and other industrial processes.
– Thermal Mass: Buildings with high thermal mass, such as those with concrete floors and walls, can absorb heat during the day and release it at night, reducing indoor temperature fluctuations.
### Factors Affecting Specific Heat Capacity
The specific heat capacity of a substance depends on several factors:
– Molecular Structure: Substances with complex molecular structures generally have higher specific heat capacities.
– Phase: The specific heat capacity of a substance can vary depending on its phase (solid, liquid, or gas).
– Temperature: The specific heat capacity of some substances can change with temperature.
### Specific Heat Capacity vs. Latent Heat
Specific heat capacity measures the heat required to change the temperature of a substance, while latent heat measures the heat required to change its phase (e.g., from solid to liquid or liquid to gas). Latent heat is typically much higher than specific heat capacity.
### Example Calculations
Example 1:
How much heat energy is required to raise the temperature of 500 grams of water from 20°C to 30°C?
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Q = m⋅c⋅ΔT
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where:
– Q is the heat energy required
– m is the mass of water (500 grams)
– c is the specific heat capacity of water (4.187 J/g⋅°C)
– ΔT is the change in temperature (30°C – 20°C = 10°C)
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Q = 500 g ⋅ 4.187 J/g⋅°C ⋅ 10°C = 20,935 J
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Example 2:
A 2-liter bottle of water is heated in the sun. If the temperature of the water increases from 15°C to 25°C, how much heat energy is absorbed by the water?
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Volume = 2 liters = 2000 milliliters
Mass = Volume ⋅ Density = 2000 mL ⋅ 1 g/mL = 2000 grams
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Using the formula above:
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Q = m⋅c⋅ΔT
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Q = 2000 g ⋅ 4.187 J/g⋅°C ⋅ (25°C – 15°C) = 83,740 J
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Therefore, the water absorbed 83,740 joules of heat energy when its temperature increased from 15°C to 25°C.