Essential Question:How are climate, cultures and oceans all connected?
On the Scientific Side
It is impossible to discuss the important function the ocean plays in absorbing and releasing thermal energy without addressing how the atmosphere interacts with the surface of the ocean. However, we will explore that role more directly in following modules. For now, we'll start with the physics of heat absorption and transfer mechanisms in the ocean.
ENGAGE
It sometimes seems as though a watched kettle never boils. And we've all shivered outside the shower before drying off. Embedded within these commonplace experiences lies a deeper truth about the nature of thermal energy and how it interacts with one of the most common substances on Earth--water.
All substances absorb, and in turn release, heat at various rates depending on the nature of the substance. To illustrate this point, place each hand on two different surfaces, for example a book and a tabletop. No doubt you notice the surfaces as having different temperatures.
But let's rethink that; both surfaces are the same temperature if they've been in the same room for a period of time. What is different is the rate at which the two surfaces absorb and release heat. This is the expression of their specific heat capacity.
For the same reason, solar energy arriving at the Earth's surface falling on both land and ocean creates dramatically different results, as daytime and nighttime temperature differences vary considerably between the two.
Because land has a lower heat capacity than water, it heats and cools more easily, becoming hot quickly during the day and cooling off quickly at night. Conversely, temperature between night and day at sea varies comparably less because water heats and cools rather slowly.
Water has an unusually high specific heat capacity; which is to say that water has to absorb quite a lot of thermal energy in order to raise its temperature. By definition, water requires 1 calorie of thermal energy input to raise the temperature of 1 gram of pure water by 1 degree Celsius.
This makes for some easy math and simple labs. Any student can easily calculate the approximate amount of heat energy absorbed or released by water by measuring the temperature change of a known quantity of water. Sounds like time for an easy lab.
EXPLORE
Does a Watched Kettle Boil? - Lab!
This is a simple lab suggestion for those who have appropriate facilities, equipment and lab safety practices. Otherwise you can follow along below and see how it demonstrates thermal transfer of heat to water and how to measure that change.
- Safety First! (Adult supervision, Goggles, Heat resistant gloves or mitts)
- Measure 100 ml (100 g) of tap water into a heat resistant beaker or similar container.
- Record temperature of the water in degrees Celsius with a safety thermometer (No Mercury).
- Place beaker on a safe heating surface and record the temperature of the water every minute until water boils and temperature does not change.
- Graph the rate of temperature change for water. (Temp on y axis and Time on x axis)
- Calculate the amount of heat absorbed by the water. (Highest Temp - Starting Temp X 100g = calories of heat absorbed by 100 ml of water)
EXPLAIN
- How much thermal energy (in calories) did the water absorb?
- Does a watched kettle boil?
EXTEND
- Why does the temperature stay the same while boiling?
EVALUATE
- How useful is this simple lab for your lessons or understanding of the heat capacity of water?
ENGAGE
Kids-Don't try this trick at home!
To further illustrate water's high heat capacity, take a YouTube look at the following NASA/JPL video, Oceans of Climate Change, comparing the heat capacity of air to water.
EXPLORE
Oceans of Climate ChangeEXPLAIN
- Why doesn't the water balloon break when held over a flame?
- How does this relate to oceans and climate?
EXTEND
- How might the concepts in the video relate to your students' learning?
- What other ways can you think of to demonstrate differences in heat capacity?
EVALUATE
- How useful was this NASA video for your grade level?
