Hurricanes > Lab 8: Hot Water and Hurricanes > 8A: Earth's Ocean: A Storage Unit for Heat

# Hot Water and Hurricanes

## Part A: Earth's Ocean: A Storage Unit for Heat

Three-quarters of Earth's surface is covered with a substance that is a very effective heat-storage materialwater. Liquid H2O can absorb and store a tremendous amount of heat energy without becoming too hot itself. The effectiveness of a substance at storing heat energy depends on a parameter called specific heat.

Specific heat is a measure of how much energy something absorbs compared to how hot it gets. More precisely, the specific heat of a substance is the amount of energy it takes to raise the temperature of 1 gram of that substance by 1 degree Celsius.

Click the picture to watch a short video by Robert Krampf. In the clip, he demonstrates a "trick" that depends on the high specific heat of water.

### Quantifying Specific Heat

Quantitative experiments show that 4.18 Joules of heat energy are required to raise the temperature of 1g of water by 1°C. Thus, a liter (1000g) of water that increased from 24 to 25°C has absorbed 4.18 J/g°C x 1000g x 1°C or 4180 Joules of energy. For comparison, alcohol (ethanol) has a lower specific heat: it takes only 2.2 Joules of energy to increase the temperature of one gram of ethanol by one degree Celsius.

To calculate the amount of heat energy gained or lost by a substance, multiply the mass of the substance by its specific heat constant multiplied by the change in temperature.

Heat energy equation:

q = m x C x ΔT

where:
q = heat energy in Joules (J)
m = mass of the substance in grams (g)
C = specific heat for that substance in Joules per gram per degree Celsius (J/g°C)
ΔT = change in temperature in degrees Celsius (°C) Change is calculated by subtracting initial temperature from final temperature (Tf - Ti)

## Stop and Think

1. Consider that the tropical ocean is exposed to direct sunlight for many hours every day. If the top 1 cm of a 100km2 area of water warms from 25 to 27 degrees, how much heat energy has the water absorbed?
Every cm3 of water has one gram of mass. To calculate the number of cm3 described, calculate the number of cm2 in the area then multiply by 1cm for the depth:
mass of water = 1g/cm3 x (1cm x 10cm/m x 1000m/km x 100 km) x (1cm x 10cm/m x 1000m/km x 100 km) x 1 cm