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CONCEPTS
- Water has a higher heat capacity than soil
and rock, so the ocean takes much longer to heat and to cool than the
land.
- Coastal areas will generally have more moderate temperatures than
inland areas because of the heat capacity of the ocean.
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MATERIALS (per group of four)
- 2 Buckets (or foil steamer trays)
- 2 Thermometers
- Water
- Sand
- Weather section of a major newspaper
- Clips (to hold thermometer in water bucket)
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PREPARATION
- Set up equipment trays for each group. Each tray should include two
buckets, two thermometers and some sand. The students will need to access
water. The bucket with water is a model of the ocean and that the bucket
with sand is a model of the land.
- Major newspapers generally have very extensive weather and almanac
sections. Such data can also be found on the Internet. Finding the appropriate
weather information might make an interesting research project for your
students. It is also possible to find the information that you need
on the Internet.
- HINT: You might wish to have the students set up the models on one
day and complete the observations on the next day. Also, this activity
may need to be performed over two class periods: one to heat the buckets,
the other to cool the buckets.
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PROCEDURE
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Engagement
- Check the newspaper weather section, and identify two cities
that are relatively close to each other: one must be on the coast
and the other must be several miles inland. This activity is best
done using regions where the wind blows from ocean to land on
sunny days. Chart the temperature range (highs and lows) of each
for a week. Have the students write a hypothesis that explains
why the temperature range of the cities by the beach seems to
be smaller than that of the inland city.
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Activity
- Have the students fill one bucket with sand and one bucket with
water. Make sure the buckets are filled to the same level. Push
the thermometer 2.5 cm (1 in) into the soil and clip the thermometer
2.5 cm (1 in) into the water. Leave both buckets in the shade
until they reach the same temperature.
- Once the temperature in both buckets is the same, put them in
direct sunlight. Check and record the temperature every five minutes
until a clear trend in the data is seen. Plot and graph the temperatures
versus time. Which bucket heated more quickly? What does this
tell us about the heat capacity (heat
energy required to raise the temperature) of water and of land?
- Move the buckets back into the shade (into a refrigerator is
better, if available). Measure and record the temperature every
five minutes until a clear trend is seen. Plot and graph the data.
Which bucket cooled more quickly? Is it the same bucket that heated
more quickly? What does this tell us about the heat capacity of
water and of land?
- Review the weather information and your hypothesis. Does the
activity that you just completed help to explain the differences
in temperature range between coastal and inland cities? Use your
graphs to compare and, if necessary, modify your hypothesis.
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Explanation
- Every day the land heats much faster than the sea, and every
night the land cools faster. When the land heats up, the air that
passes over it heats up. The ocean heats up and cools down much
more slowly. This means that the air over the ocean does not heat
up as much or as quickly as the air over the land. Therefore,
areas near the ocean generally stay cooler during the day and
have a more moderate temperature range than inland areas. This
is why we say that water has a higher heat capacity than land‹it
takes more time (i.e., more energy) to warm and to cool it by
a given amount.
- Heat capacity is the amount of energy required to raise the
temperature of a substance by 1°C. Thus, larger bodies of
water have higher heat capacities than smaller bodies. To compare
substances directly, scientists often refer to the heat capacity
per unit mass, known as the specific heat.
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EXTENSION
- The farther a region is from the ocean, the more extreme its climate
is likely to be. A continental summer is hotter than a coastal summer,
and a continental winter is colder than a coastal winter. Coastal climates
tend to be more moderate. Some ocean currents bring cool water and some
bring warm water, which also influences coastal climates.
- Large lakes, such as the Great Lakes, can also influence the temperatures
at lakeside cities in similar ways, though generally not as much as
the ocean.
- Do your students live near or far away from a large body of water
(i.e., an ocean or very large lake)? Have them adopt a city in the opposite
climate region with about the same latitude. (In other words, students
who live near an ocean or large lake should find a city that is far
from an ocean or large lake, and vice versa). Using newspaper weather
data, the Internet, and/or an almanac, have them compare their weather
and climate to that of their adopted city over time. What factors influence
different weather in each place? Is proximity to a large body of water
the main driver of weather in your regions?
- Your students may wish to do this exercise with a number of cities.
If so, be sure to include cities on both the west and east coasts of
a continent (this may be easiest for North American cities). How does
the relative temperature of major currents of each coast affect each
coastal city's climate?
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VOCABULARY
- heat capacity: amount of heat required to raise the temperature
of a substance by a given amount.
- model: system of data, inferences, and relationships, presented
as a description of a process or entity.
- specific heat: the quantity of heat required to raise the temperature
of 1 gram of a given substance 1°C. For water it is 1 calorie.
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SOURCE
- "Visit to an Ocean Planet" educational CD-ROM, Copyright
Caltech and NASA/Jet Propulsion Laboratory
- Adapted from Allaby, Michael. How the Weather Works. Reader¹s Digest
Association, Inc. 1995. p. 146 - 147.
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