Will Global Warming Cause Sea Level Rise - Mallek AbdeRRAHMANE

8/9/2019 Will Global Warming Cause Sea Level Rise - Mallek AbdeRRAHMANE

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Will Global Warming Cause a Rise in Sea Level?

A Simple Activity about the States of Water

Ayse Oguz

Abstract: In this activity, a possible problem related to

global warming is clarified by the principle of states of

water. The activity consists of an experiment that includes

three scientific principles: Archimedes’ Principle, the Law

of Conservation of Matter, and the fluidity of liquids.

The experiment helps students raise questions and opennew horizons of curiosity in their minds. It forms bridges

between the mind and senses in the physical world and

encourages integrated thinking in science. The experiment

could easily apply to any school level, including elementary

or middle school, and in any context.

Keywords: global warming, integrated thinking, scientific

inquiry, states of water

ecause of water’s unique physical and chemical char-

acteristics, its chemical and physical properties are

fundamental to many scientific disciplines, such as

chemistry, physics, hydrology, environmental studies, andeven civil engineering. Water is one of the few substances

that can be found naturally on Earth in all three states of

matter: solid, liquid, and gas.

AYSE OGUZ teaches in the science education department, part of the Faculty of Education at Mugla University in Mugla, Turkey. E-mail: [email protected]

Copyright © 2009 Heldref Publications

As liquids cool, their molecules lose heat energy and move

more slowly. This allows molecules to move closer together,

becoming denser and reducing the liquid’s volume. This

means that a cold liquid will sink, and a warm liquid will rise.

Because the molecules of cold liquids are closer together,

they support the less dense, warmer liquid above. As a result,liquids freeze from bottom to top. However, what happens

when water gets cold enough to turn to ice?

I started my seventh-grade science class with the pre-

ceding explanation. The concept of the states of water is

important but sometimes difficult to develop. Therefore,

following the explanation, I prepared an experiment.

Experiment

Fill a beaker or glass halfway with water, mark the water

level (see Figure 1), and then add ice cubes. The ice cubes

will float, and the water level will rise as much as the dis-

placed volume of the ice cubes. Mark the new water level

(see Figure 2). Leave the ice cubes to melt at room tem-

perature. While the class waits for the results, ask studentsto hypothesize what will happen to the water when all the

submerged ice cubes have melted. Will there be more or

less water than there were ice cubes? Will the melting of

the ice cubes cause the water to spill out of the container?

Will the ice cubes melt and increase the water level just a

little compared with the original level? Will the water level

remain the same?

17

B



Without editing the answers, record students’ ideas on

the board. As more suggestions are accepted without either

positive or negative comment, students will see that it is

safe to offer ideas, and they will be willing to share their

hypotheses.

As the ice melts, the water level decreases slightly from

its level when the ice cubes were submerged. (See Figure

3.) Because ice is extremely cold water, one may expect the

molecules to move little and be close together. However,

one need only put a plastic bottle full of water into a freezer

to observe that freezing water expands so much that the

plastic bottle may break. When water freezes, the molecules

spread out and are arranged in a lattice-like pattern (Council

for Environmental Education and Montana State Univer-

sity 2000). This formation increases the distance between

water molecules and the volume of the ice, making it less

dense than water. Archimedes’ Principle states that a body

immersed in a fluid is buoyed up by a force equal to theweight of the displaced fluid. This lifting force depends on

two variables: density of a liquid and immersed volume of

the body. Following Archimedes’ Principle, the ice cubes

float, and the water level rises only as much as the displaced

volume of the ice cubes.

In lakes and rivers, the water on the surface freezes,

whereas the water below remains liquid. In the winter,

aquatic life survives under the ice because the ice floating

18 SCIENCE ACTIVITIES Vol. 46, No. 1

FIGURE 1. Half-filled beaker of water.

FIGURE 2. Water with ice cubes. FIGURE 3. Water with melted ice.



on the surface of the body of water acts as an insulating bar-

rier, moderating the temperature of deeper water.

A Student’s Dilemma

The study of solids, liquids, and gases is a common but

sometimes difficult concept to develop for students. After

doing the experiment described, one student remarked:

Many scientists predict that if changes in global climateincrease world temperatures, then icebergs will melt, andsea levels will rise. They claim that this would bring aglobal problem to the direct attention of individuals livingin coastal areas. However, by looking the results of theexperiment, I do not believe the scientists are telling thetruth about global warming.

The student showed a picture of an iceberg floating

on the ocean and continued, “Let’s look at the picture,

the iceberg floats on the ocean. We can accept that the

iceberg is like the ice cubes swimming in the cup.”She asked how global warming will increase sea levels

because the result of the experiment with the ice cubes

supports the opposite idea: water levels will decrease,

not increase, as ice melts.

The student’s question created doubt about whether

global warming would cause sea levels to rise. Other stu-

dents in the laboratory became animated as they debated

their classmate’s suggestion. One student said, “This is also

true in terms of the Law of Conservation of Matter.” During

an ordinary chemical change, there is no detectable increase

or decrease in the quantity of matter. The total quantity

of matter and energy available in the universe is a fixed

amount, never any more or less. “Therefore,” concluded the

student, “the amount of water cannot be changed.” Anothersaid, “These experts cannot all make the same mistake.

Water plays a prominent role in a many of the events we

call natural disasters.”

The situation opened new horizons of curiosity in the stu-

dents’ minds. Within the scientific thinking process, I guided

the students’ discussion with the following questions:

What do we know that is related to this dilemma?

As a systematic guidance teacher, I try to help students

build bridges between the pieces of information. As the stu-

dents had mentioned, two scientific principles—Archimedes’

Principle and the Law of Conservation of Matter—support

the idea that global warming will not cause sea levels to

rise. When water freezes, the molecules spread out and arearranged in a lattice-like pattern that causes the ice cubes

to float and the water level to rise as much as the displaced

volume of the ice cubes (based on Archimedes’ Principle),

and the total amount of water cannot be changed (based

on the Law of Conservation of Matter). However, many

experts predict that sea levels will rise. Thus, some pieces

of the puzzle must be missing.

What other factors should we consider?

I helped students consider this question through inves-

tigation. I placed one big ice cube in the middle of a flat

cup and allowed it to melt. The students observed that themelted water expanded to the sides as it took the cup’s

shape. From this experiment, they saw that one missing

piece of the puzzle was the fluidity of liquids.

Water flows over the Earth’s surface, seeps underground,

freezes, and evaporates. It moves through the atmosphere as

vapor and eventually falls back to Earth, sometimes many

miles away or in different climates. Global warming is one

factor that can affect this cycle. Global warming leads to

warmer temperatures, which cause water to expand. When

water expands in the ocean with warmer temperatures, it

takes up more space, and the level of the sea rises. Warmer

temperatures also cause mountain glaciers, small ice caps,

and parts of larger ice sheets to melt, adding more water to

the ocean.

What conclusions can we draw?

As a conclusion, global climate changes increase world

temperature, and higher temperatures are expected to raise

sea levels by

• expanding ocean water

• melting mountain glaciers and small ice caps

• causing portions of the coastal section of the Greenland

and Antarctic ice sheets to melt or slide into the ocean

(U.S. Environmental Protection Agency, 2008).

However, climate models, satellite data, and hydrographic

observations demonstrate that sea levels are not risinguniformly around the world. Depending on the region, sea

levels have risen several times the global mean rise, or have

actually fallen. Although current model projections indicate

substantial variability in future sea level rise at regional

and local scales, the Intergovernmental Panel on Climate

Change has concluded that the impacts are “virtually cer-

tain to be overwhelmingly negative” (2007).

Science requires integrated thinking, or thinking about

scientific principles as a whole. The overall goal of science

is to investigate nature, which functions as a whole. There-

fore, for example, principles for physics also hold true for

chemistry, biology, and geography. Three larger principles

support the assertion that global warming will increase sea

levels. First, when the motion of the molecule increasesbecause of an increase in heat energy, water will change

from solid to liquid to gas. Physical movement from one

location to another usually follows each change in state.

This cycle of water proves the Law of Conservation of

Matter. Second, when water freezes, the molecules spread

out and are arranged in a lattice-like pattern. Therefore, ice

floats on water because of Archimedes’ Principle. Third,

Spring 2009 SCIENCE ACTIVITIES 19



when the ice cubes melt into a liquid, they show the proper-

ties of fluidity.

Implication for Science Education

Encouraging students to ask questions and focusing on

their inquisitiveness will facilitate thorough investigations

(Harlen 2001). In some cases, the questions may not be

answered, or more questions may arise. Results may even

be erroneous. However, asking questions enables students to

observe, inquire, form hypotheses, experiment, use testing

activities, and verbally share information with others. In this

process, they begin discovering and observing the world like

scientists, as well as forming bridges between the mind and

senses in the physical world. Active participation draws us

closer to our complex world and helps us discover simpler

paths. Therefore, we need to devise activities concerning the

foundation of science education on the basis of this simple

approach for students, beginning at an early age.

When students ask questions, it means that they want to

know and are interested. Some questions will be difficult

for teachers to deal with, but it is important to find a way

of doing so that does not make the student wish he or she

had not asked. After all, decision making and problem solv-

ing are critical thinking skills necessary for productive and

responsible citizenship.

References

Council for Environmental Education and Montana State Uni-versity. 2000. The Project WET curriculum and activity guide. Bozeman, MT: The Watercourse.

Harlen, W. 2001. Primary science taking the plunge. Portsmouth,NH: Heinemann.

Intergovernmental Panel on Climate Change (IPCC). 2007. IPCCReports. http://www.ipcc.ch/ipccreports/index.htm (accessedNovember 26, 2008).

U.S. Environmental Protection Agency (USEPA). 2008. Coastalzones and sea level rise. http://www.epa.gov/climatechange/

effects/coastal/index.html (accessed November 26, 2008).

20 SCIENCE ACTIVITIES Vol. 46, No. 1



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Will Global Warming Cause Sea Level Rise - Mallek AbdeRRAHMANE