Worksheet 1.
Worksheet 1.
Antarctic Ice
Read the passage below and then answer the questions following it. The excerpt is from the book Antarctica written by Colin Monteath, an author and photographer who has travelled and worked in the Antarctic for over 20 seasons.
Antarctica covers 10% of the world's surface, an area equal to the USA and Mexico combined. Its harsh environment locks 70% of the world's fresh water into ice sheets, in places over 4 km deep; yet a unique ecosystem supports one of the richest concentrations of wildlife in the world
The modern-day Antarctic ice sheets consist of about 30 million cubic km of ice spread over an area of 14 million square km - nearly twice the size of Australia. Only a smattering of rocky summits and coastal ice-free areas avoid complete inundation by this blanket of ice. Many of Antarctica's glaciers take on enormous proportions. The world's largest glacier, the Lambert, situated near the Australian science bases Davis and Mawson, is 400 km long by at least 100 km wide. The Lambert is further extended where it flows out to sea to form the Amery Ice Shelf. If the weight of Antarctic ice was removed from the continent, the land would rise from 300 m to 1000 m. In fact, Antarctica's incredible mass causes the Earth to be slightly pear-shaped.
Antarctica is divided into the West and East Antarctic ice sheets by the 3000 km long Transantarctic Mountains which are up to 4500 m high. Much of the West Antarctic Ice Sheet rests on bedrock that is well below sea level. The East Antarctic Ice Sheet by comparison is much larger and rests on a base that is predominantly above sea level. Massive ice domes in East Antarctica reach up to 4000 m. The North Pole and surrounding Arctic Ocean are often referred to by geographers and map-makers as the 'top of the world'. In reality, with the Geographic South Pole at over 3000 m and with a mean elevation of over 2000 m, Antarctica is by far the highest of all continents.
In 1995 a single iceberg
measuring 77 km by 37 km and 180 m thick broke away from the Larsen Ice Shelf
to drift northwards into the Weddell Sea. An even larger one, 154 km by 36 km,
cut loose from the Ross Ice Shelf in 1987.
Questions
1.
The
area of New Zealand is 269 000 km2. How many times bigger than New
Zealand in area are the modern-day Antarctic ice sheets?
2.
The
area of the North Island of New Zealand is 115 000 km2. What percentage
of the North Island could the Lambert glacier cover?
3.
Some
people have suggested that countries could obtain fresh water by towing
icebergs from polar regions to their countries. In this problem you will
calculate what sort of water supply could have been obtained from the 1995
iceberg mentioned above.
a) Find the volume of this iceberg in cubic metres.
b) Convert this volume into litres.
c) Suppose that one quarter of this volume gets lost through melting and poor handling of the iceberg and that only three quarters of it is converted to useful fresh water. Suppose further that each person needs three litres of fresh water each day for drinking and cooking purposes. How long would this iceberg last if it was used to keep the entire world (population 4 billion people) in fresh water?
4.
These
days there is much concern about global-warming and how this could affect the
level of the world's oceans. In this problem you will calculate what could
happen to the level of the world’s oceans if the Antarctic ice sheets melted.
The total area of all the world's oceans is 360 million square kilometres. The
density of water is 1000 kg m-3.
The density of ice is 916 kg m-3.
a) The
Antarctic ice sheets have a volume of 30 million cubic km. Convert this volume
into cubic metres.
b)
What
mass of ice is contained in the Antarctic ice sheets?
c)
What
mass of water would this ice produce if it melted?
d)
What
volume of water would be produced from the melted ice above?
e)
Convert
the area of the world’s oceans into square metres.
f)
What
height increase would this produce in the world's oceans?
g)
Actually,
there are some reasons why the height increase would not be quite this much,
even if all the Antarctic ice sheets did melt. State these reasons.
h)
How
would this increase in the height of the oceans directly affect the area you
live in?
i)
Considering
the global effects of the increase in the height of the oceans, how would this
affect your lifestyle?
Worksheet 2
Surviving In Antarctica, The World’s
Coldest Continent.
Part One: What to wear outside
Inside Scott Base people can wear normal clothing such as jeans and tee
shirts because the Base is centrally heated.
Outside, the situation is, of course, very different. Clothing worn outdoors must protect people
against four things: cold, wind, precipitation, and sun. Since outdoor conditions and activity levels
can change, it is important to have versatile clothing. This is best achieved by having a range of
layers of clothing to choose from. For
example, a person who has just one very thick and warm jacket is likely to be
often too warm (when they are wearing the jacket) and often too cold (when they
are not wearing the jacket).
The
extreme cold of Antarctica makes it very important to prevent people losing
body heat. Heat loss occurs through
conduction and convection. The warmest
clothing will be made of a poor conductor of heat and will also prevent
convection currents occurring in air near to the body of the wearer. For example, down is an excellent insulator
and is frequently used in clothing and sleeping bags. The down traps a still layer of air and prevents it
circulating. Actually, most clothing
provides insulation by trapping a still air layer. Thus heat cannot be lost by convection, although this picture can
change if the down is exposed to wind.
Also, down is a very poor conductor of heat and so very little heat is
lost by conduction. Since down is so
light, even a thick insulating layer of has very little weight. However, down is not the perfect insulator:
wet down is virtually useless at providing insulation, as anyone who has
attempted to sleep in a wet down sleeping bag will know! Further, down is much more costly than a
number of synthetic products which perform better in wet conditions.
Below, you will find two clothing lists. One
is for Antarctica. It is from the Antarctica New Zealand website:
http://www.antarcticanz.govt.nz The
other list is for tramping in New Zealand.
It is designed to be adequate for conditions where cold, wet and windy
weather may be encountered. However, it
is not designed to cover situations where significant snow may be met. As you read through these two lists you will
notice some similarities but also some differences.
Clothing worn in Antarctica
Long johns in wool or polypropylene
(top and bottom)
Salopettes (these are
trouser overalls made of polar fleece)
Polarfleece or wool
shirt
Windproof Anorak that
may have a fur lined hood. Most often it just has a windproof hood
Windproof trousers
Down overall style
trousers - this is like wearing a thick heavy sleeping bag made into overalls
Down jacket - this is like
wearing a thick heavy sleeping bag made into a jacket
Sunglasses or goggles
- to prevent snow blindness and eyestrain from the 24 hour per day sun in
summer
Woollen hat or
balaclava - sometimes with a thinner polypropylene hat underneath
Neck gaiter - a
tube of polypropylene that goes over your head and round your neck to keep your
neck warm and prevent drafts going down your shirt.
Windproof hat with ear flaps over
top
Gloves - a
combination of thin polypropylene with wool gloves on top with large nose wiper
mittens on top. A cord around the neck attaches the nose wiper mittens so that
they can be removed when you need to use your hands without dropping or losing
them. If they were dropped onto the ice/snow they would freeze solid.
For heavy outside work
leather gloves are used
Windproof gloves or
mittens may go over the top of the woollen gloves
Very thick woollen
socks
Quilted liners (like
slippers)
Mukluks - large
boots with heavy soles and leather padded lining inside. These come up to mid-calf
and have quilted padding all the way up inside.
Tramping boots (ones
you have tramped in before)
Socks for boots plus
one change of socks for boots
Gaiters for boots
Parka (waterproof,
with a hood and of good length)
Shorts for tramping
in
T-shirts for tramping
in
Polyprop longjohns
and polyprop top
Two layers of wool or
similar to wear on your top half while tramping: e.g. jersey plus polarfleece
jacket.
Gloves or Mittens
1.
Name the four
things that clothing must protect people against when they are outdoors in
Antarctica.
2.
Give
three reasons why the sun can be particularly damaging to people working in outdoors
in Antarctica.
3.
Explain why it
could be better to have two thin garments rather than one thick garment of the
same warmth.
4.
Frequently,
people in New Zealand reduce the heat loss from their homes by putting
fibreglass Batts inside their hollow walls. However, air is already a very poor
conductor of heat. How is it possible, then, that these fibreglass Batts can
reduce heat loss so significantly?
5. Dry down is an excellent insulator. Why do think wet down is such a poor insulator?
6. Look at the list of clothing worn in Antarctica. There are four of items of clothing that can be worn to protect the legs. List these four items, starting with the innermost layer and finishing with the outermost layer.
7.
A
waterproof parka is listed for tramping in New Zealand but it is not mentioned
on the list of clothing worn in Antarctica. Why is this?
8.
Look
at the list of clothing for tramping in New Zealand. Which item on the list
would offer the best protection against wind?
9.
The
list for Antarctica mentions five items that offer particular protection
against the wind. List these items. Why is wind much more of a problem in
Antarctica than it is in normal tramping situations in New Zealand?
10.
Explain
why an igloo or a snow cave would provide better insulation against the cold
than a tent in Antarctica.
11.
When
tenting out in New Zealand, people often sleep on thin foam mattresses. When
tenting out in Antarctica, everyone uses thick foam mattresses. Why is this?
12. Sewerage and grey water from Scott Base are discharged into the sea through a pipe. All other wastes are returned to New Zealand. What special precautions would need to be taken with the waste pipe?
13.
Sometimes goggles would provide better protection than
sunglasses. When would this be?
14. We see that down clothing is on the list for Antarctica but not on the list for New Zealand. Give two reasons why such clothing is not on the New Zealand list.
15.
There
are three ways in which heat energy can be transferred from one place to
another. We have already mentioned two of these ways: conduction and
convection. The third way is also very important because it is the only way in
which heat energy can come from the Sun to the Earth. What is the name of this
third way? However, humans lose very little body heat by this third heat
transfer method. Why is this?
16. In 1993, Sir Ranulph Fiennes and Dr Michael Stroud completed the first unsupported crossing of the Antarctic Continent. This incredible feat of endurance took 97 days and involved them each dragging sledges of mass in excess of 200 kilograms. In his book Mind Over Matter Sir Ranulph Fiennes states, “Avoiding perspiration is my chief aim when selecting clothes”. Give two reasons why you think he was so concerned about avoiding perspiration.
Worksheet 3
Surviving In Antarctica, The World’s Coldest
Continent.
Part Two: Surviving a Storm
Your team
has been assigned to drill ice cores 40 km from base camp. You have just
completed a week of survival training and know that it is essential to bring
individual survival packs in case of an emergency situation. Freak storms can happen without warning. You
might need to wait out a storm that prevents you from moving to safety, and
prevents rescue teams from reaching you.
Your team must decide which items to put in the packs so that each team
member could survive in severe weather for 24 hours. Choose carefully: your life might depend on it! Read the list of possible items for
survival and decide which you think are essential. Use the Antarctic conditions fact sheet
below to help make decisions.
Your main
goals are to:
· Protect your body temperature
· Ensure a source of fluids
· Ensure a source of calories
As a group,
decide which ten essential items you will bring. Each pack must contain:
· The same eight items per individual
agreed on by all group members
· Two additional items, which
will be shared by the group. These two
items should be different for each member's pack
pack camera
flashlight matches
drill snow
shovel/ice saw
tent sleeping
bag
half a loaf of bread snowshoes
journal/pencil
backpacking
stove/kerosene
2 litres of water cheese
beef jerky
book
chocolate bar picture
of someone you love
mittens/socks/face mask scroggin
(nuts and raisin mix)
signal mirror rifle
thermal sleeping pad blanket
suntan lotion insect
repellent
dehydrated food
cup/spoon
individual first-aid kit pot
and pan set
sledgehammer radio
with spare batteries
toilet paper
Ice and snow
cover 98 percent of the continent.
Winter extends from May
through August. Summer extends from December through February. Temperatures
during January and February range from -15°C to -35°C inland, and reach up to
0°C along the coast. Antarctica's inland plateau has been called a polar
desert. Very little moisture is in the air there, so dehydration can be a major
concern for people working on the ice.
Winds range from about 8
km/h to 64 km/h. Below-freezing temperatures and high winds can lower the
temperature to -100°C and decrease the visibility to less than 30 m.
Storms arrive quickly. They
can be very localized: the sun might be shining in one area while a severe
snowstorm is happening just 80 km away. Blowing snow can create
"whiteout" conditions with zero visibility. Low clouds on the horizon
contribute to low visibility and make it hard to see crevasses and cracks in
the ice. When in unknown territory, it is advised to stay put during a storm.
Due to the polar location,
continuous daylight occurs during the summer, the time when scientists conduct
their research.
Worksheet 4
Surviving In Antarctica, The World’s
Coldest Continent.
Part Three: How Wildlife Survives
The extreme environment of the continent of Antarctica is too harsh for most life forms. Air temperatures average well below zero all year round and strong winds increase the effects of the cold temperature. During winter there are months of total darkness while during summer there are months of total sunlight, frequently with very high levels of UV radiation. In spite of the fact that all but two per cent of the continent is covered with ice, there is very little free water. Only very small and primitive plants and animals can handle the extreme conditions mentioned above.
However, we do find abundant life in the surrounding ocean. This is because conditions for all living things there are far better than on the land. The water is still very cold but at least remains fairly constant in temperature. There is no wind. There is a large supply of nutrients. This is because the Antarctic waters of drift north and, when they meet warmer waters, the Antarctic waters sink. As they sink, they stir up nutrients and minerals from the bottom of the ocean. These nutrients in the water are used by organisms called phytoplankton. These single-cell floating plants carry out photosynthesis, using the Sun's energy, water, and carbon dioxide dissolved in the water to form glucose and oxygen.
Krill are the next link in the food chain. Krill are hard-shelled animals like shrimp, about seven centimetres long. They live off the phytoplankton. In winter, however, there is very little light and therefore the production of phytoplankton is very limited too. To cope with this, scientists believe that krill either become cannibalistic or shrink and use up their own body's reserves. Krill occupy a key position in the food chain. They are eaten by seals, penguins, fish, squid and whales. Luckily for these consumers, krill is the most abundant animal in the world. It is easy prey, being found in swarms several kilometres long.
There are about 20 000 species of fish in the world but only about 200 of these are found in the Antarctic sea. The temperature of the water in the Southern Ocean is in the range -2 oC to 0 oC. Pure water freezes at 0 oC. However seawater contains much dissolved salt and this lowers the freezing point. Fish also contain water. This water inside the fish does not freeze because it also contains dissolved salts that lower the freezing point. Some fish also contain glycoproteins that operate like anti-freeze and inhibit the growth of ice crystals. Normal fish, and in fact all other vertebrate species, contain haemoglobin in their blood to carry oxygen around their bodies. Some Antarctic fish (the so-called icefish) have no haemoglobin in their blood, but oxygen can still be carried because it is highly soluble in cold fluids, including blood. The relative paucity of red blood cells (which normally are loaded with haemoglobin) makes the blood thinner, and easier to circulate, thus conserving energy. Antarctic fish also have very efficient enzyme systems that allow them to remain active at low temperatures. Their activity at 0 oC is similar to that of a normal fish at 20 oC. To cope with the low light levels under the water that, (ice and snow limit light penetration), many fish species have large eyes and also a well-developed sensory system (lateral line system) to help them locate food.
Birds have the advantage of being highly mobile. They can breed on land, feed from the ocean, and migrate north to avoid the extremely harsh winters. Some penguins breed on the mainland rather than on the warmer sub-Antarctic Islands,. To cut down heat loss, they rely on their overlapping feathers, a layer of fat under the skin, small extremities, and a rounded body shape. The rounded body shape reduces the surface area for a given volume. A reduced surface area is important because all heat loss occurs through the surface. The ideal shape would be a sphere: a sphere has the smallest surface area of any shape for a given volume. Three of the four Antarctic penguin species avoid the worst of winter by remaining at sea. The one exception is the emperor penguin, which breeds in autumn. The males then spend two months huddled in groups incubating the eggs. They keep the eggs balanced on top of their feet. The penguins take turns being on the outside of the group. In this way they can survive temperatures averaging -20 oC and frequent strong winds. These penguins also have a heat exchange system in their legs. Without this system, hot blood from the heart would flow into their feet and much heat would be lost to the ice on which they are standing. With this system, hot blood from the heart flows near to cold blood coming back from the feet. Heat is then transferred from the hot blood to the cold blood. This heat is not lost to the ice but instead stays with the penguin.
Penguins have extremely good insulation and in summer they can sometimes be in danger of overheating, particularly when they are active and the weather is fine. In this situation they often raise their flippers. The layer of fat underneath their flippers is relatively thin so heat loss is increased. Heat loss is further increased by boosting warm blood flow to this area. They can also increase their heat loss by altering the blood flow in their legs so that warm blood is circulated directly to their feet.
Seals and whales have similar adaptations to those mentioned above. They have a rounded body shape that has a small surface area to volume ratio, thus reducing heat loss. They are insulated by a thick layer of blubber and they have small extremities. All Antarctic whales migrate north in winter in search of food: in winter. In summer, seals gain heat by basking in the sun on ice floes.
Algae are the main type of plant found on land in Antarctica. Their simple, tiny cellular structure is able to withstand long periods of freezing. In summer they may be flawed and frozen several times a day. Algae can be found on and under rocks, on areas of permanent snow, and at the bottom of lakes. Lichens have been found within 400 km of the South Pole. Although they do contain anti-freeze compounds in their cells, and can function with less light and water than other plants, they recover very slowly from freezing after winter. Recently New Zealand scientists discovered lichens photosynthesising at -20 oC, the lowest ever recorded.
1. In Antarctica, is most life found on the land or in the water? Explain carefully why this is so.
2. Phytoplankton are the first living organisms in the food chain. On what do they feed?
3.
Krill
is an important link in the food chain. List the organisms that rely upon krill
for food. Why are krill less plentiful in winter?
4.
Antarctic
fish live in sub-zero temperatures. How do they prevent the water inside them
from freezing? Give two ways in which they do this.
5.
What
important task is normally carried out by haemoglobin in blood? How is it that
Antarctic fish can carry out this task without haemoglobin? What advantage is
there for these fish in not having haemoglobin in their blood?
6. List four ways in which penguins minimise heat loss.
7. How do emperor penguins keep eggs warm in winter?
8.
Emperor
penguins huddle together in winter. Explain carefully, in a proper scientific
way, what the advantage is in this group behaviour.
9.
Sometimes
in summer penguins get too hot. Describe two ways in which penguins can
increase the amount of heat they lose.
10. Give three ways in which whales minimise their heat loss.
11.
In
winter, whales migrate north because there is not enough food in Antarctic
waters for them. Carefully outline the chain of events that, in winter, results
in insufficient food for whales.
12.
Some
humans have established permanent homes in Antarctica. Where in Antarctica do
you think their homes might be? Reference to a map of Antarctica could help you
answer this question.
13.
A
group of scientists is planning to stay twelve months at Scott Base. What
special problems must they overcome in order to do this successfully? Explain
how you think they could overcome these problems.
14.
Polar
bears and other animals live and thrive in Arctic regions. Give some reasons
why no such animals are found living in Antarctica.
Worksheet 5
Surviving In Antarctica, The World’s Coldest
Continent.
Part Four: Under The Ice
Antarctica is by far the coldest continent. The world's lowest recorded temperature (-89.2o C) was
measured in 1982 at Vostok Station (Russia) on the high inland ice sheet. Mean temperatures of the coldest months are
-20o C to -30o C on the coast and -40o C to
-70o C in the interior.
Midsummer temperatures range from a mean of about 0o C on the
coast to between -20o C and -35o C in the interior. These temperatures are far lower than those
of the Arctic. How can creatures living in the sea or in lakes survive such low
temperatures? And why doesn’t the water
all turn to ice?
The answers to these questions depend in part on some very strange properties of water. The Encyclopaedia Britannica describes water as “an extraordinary substance”. For example, ice is actually less dense than water. This is most unusual: almost all substances become denser when they freeze. There is another unusual fact about the density of fresh water. As water cools it becomes denser until it reaches a temperature of 4o C. At this temperature it has maximum density. As the water becomes still cooler it decreases in density.
In seawater, the salt changes this
picture in two ways. Firstly, the more
salt the lower the freezing point.
Typical seawater freezes at about –2o C. Secondly, in seawater, as the temperature
decreases, the density keeps increasing until the water freezes.
The exercises
below will help you understand how these strange properties of water enable
survival in sub-zero temperatures. Copy
out the sentences in each exercise and complete them by choosing one word from
the words given in the brackets.
1.
Imagine a lake of fresh water in winter. The water on the top of the lake is exposed to the cold air above
and cools. This decrease in temperature results in an (increase/decrease) in
density. This (increase/decrease) in
density causes the water to (rise/sink) to the (top/bottom) of the lake. Warmer, (more/less) dense water then moves
up to the (bottom/top) of the lake.
This water in turn is (heated/cooled) and descends to the bottom. In this way, a
(conduction/convection/radiation) current is set up in the lake. It is easy to cool the lake down because the
(coldest/warmest) water always comes to the top where it is exposed to the
(warm/cold) air.
2. The above exercise explains what really does
happen in freshwater lakes and in seawater until the temperature reaches 4o
C. Until this temperature is reached
cooling can take place easily because (conduction/convection/ radiation)
currents help it. Let us now imagine
that water has no strange properties.
In this case the currents would continue to aid cooling until the water
temperature reaches (boiling/freezing) point.
As the top layer of water (melts/freezes) small pieces of ice would be
formed. In this imaginary situation,
these pieces of ice would be (more/less) dense than the water and so they would
(sink/rise) to the (top/bottom).
(Ice/Water) in the top layer would continue to (melt/freeze). These new pieces of ice would also sink to
the bottom. In this way eventually all the water would freeze. Once this had happened, most life would
(continue/cease).
3. Luckily, what really happens in freshwater
lakes below 4o C is different.
Suppose the whole lake has reached a temperature of 4o
C. The cold air above the lake
(heats/cools) the (top/bottom) layer of water.
Suppose it is cooled to 3o C. Now it is (more/less) dense than the rest of the water and so it
(does/does not) sink to the bottom. No
more convection currents can take place. The top water layer can continue to
lose heat to the (air/ice). Lower water
layers must lose heat by (conduction/convection/radiation) to water layers
above them. Water is actually a poor
(conductor/convector/radiator) of heat and so heat loss is (fast/slow). When the top of the lake reaches (100o
C/0o C) it freezes. The ice
that is formed is (more/less) dense than the water and so this ice floats on
the surface. Eventually a layer of ice
may be formed that covers the complete lake. Ice is also a poor (conductor/insulator)
of heat and so it acts as a good (conductor/insulator), protecting the water
below. While the top of the lake is
(frozen/liquid), the bottom of the lake may maintain a temperature of (0o
C/4o C). Thus, life in the
lake (can/cannot) continue.
4.
With seawater, warmer water is always (less/more) dense than colder
water, and so the convection currents continue to bring warmer water to the top
layer until the top layer freezes. This
layer of ice remains on the top of the ocean, being (less/more) dense than the
water beneath. Because it is a poor (conductor/insulator) of heat, the ice forms a good (conducting/insulating) layer, protecting
the water below it. Any snow that may fall on the ice further aids this
protection. As more water freezes the
ice layer becomes (thicker/thinner) and provides (better/worse)
insulation. Seasonal sea ice rarely
becomes more than about two metres thick.
As water freezes it contains very little
salt: the only salt it contains is in small amounts of seawater trapped in
pockets in the ice. As a result, the
remaining seawater underneath the ice contains even (less/more) salt. This (decreased/increased) concentration of
salt (lowers/raises) the freezing point of the remaining seawater making it
(easier/harder) to freeze. The low
temperature and the increased salt concentration of the top layer of water both
make it (more/less) dense, causing it to (rise to the top/sink to the bottom)
of the ocean. This continued convection
current keeps the water circulating. As
a result of this not just the top layer but all the water in the ocean must be
cooled to the new lower freezing point before any more freezing can occur. Once the ice becomes more than about
(ten/two) metres thick this is very difficult to achieve because the thick ice
layer is such a good (conductor/insulator).
In this way the ocean remains largely (frozen/unfrozen) and life
(can/cannot) continue in it. Further south it is (warmer/colder) and the sea
ice can be (thicker/thinner). For
example at latitude 78o S, McMurdo Sound has sea ice several metres
thick. I n spite of this, Weddell seals are able to maintain breathing holes
through the (summer/winter) by gnawing away at the ice.
Worksheet 6
Experiment: Staying warm in cold
places.
A person working outdoors in Antarctica can lose a lot of body heat in a short time. This is because there is a large temperature difference between their body (37o C) and their surroundings (-30o C in the Antarctic interior in midsummer!). In order to minimise this heat loss, people in Antarctica wear thick insulating clothing. This experiment explores these two ideas.
1. To find how the rate of heat loss depends on the temperature difference.
2. To find how the rate of heat loss depends on the thickness of insulation.
Please read this method through completely before it you start carrying it out. It may need to be varied depending on the amount and type of equipment that you have.
1. Find three containers such as beakers or cans of the same size and shape. Into each put the same amount of hot water, the hottest water you can obtain.
2. Cover each container with a lid made of cardboard or similar. Through a small hole in this lid put a thermometer so that the temperature of the water can be measured.
3. Leave the first container as it is. Wrap insulation around the second container, including the top and the bottom of the container. Wrap the same sort of insulation around the third container, making sure that it is twice as thick as the insulation wrapped around the second container.
4. For each container, record the temperature as they cool down at one-minute intervals.
5. Continue this recording for as long as you can until the temperature is not changing much from one reading to the next.
6. Measure the room temperature.
7. Set out your results in a table like the one below. You will need more lines in your own table.
8. Graph your results on a full-page graph. On the vertical axis put temperature. On the horizontal axis put time. Plot the results for all three containers on the one graph so that it is easy to compare the three sets of results.
Room Temperature: o C
|
Time (minutes) |
Temperature (o C) Container with no insulation |
Temperature (o C) Container with single insulation |
Temperature (o C) Container with double insulation |
|
0 |
|
|
|
|
1 |
|
|
|
|
2 |
|
|
|
|
|
|
|
|
Consider just the container with the single layer of insulation.
1. When is the container losing heat fastest?
2. How does the gradient of the graph show us how fast the container is losing heat?
3. Calculate the value of the temperature 40o C above room temperature. How long does it take the container to cool down 1o C from this temperature?
4. Calculate the value of the temperature 20o C above room temperature. How long does it take the container to cool down 1o C from this temperature?
5. Read the first aim of this experiment again. Write a conclusion for this experiment based on this aim.
Now consider all three containers.
1. Which container cooled down the fastest?
2. Which container maintained its temperature the best?
3. From the results in your table, calculate the temperature decrease for each container in the first five minutes of the experiment.
4. From your graph, determine how long it took each container to reach a temperature of 30o C.
5. Reread the second aim of this experiment. Write a conclusion for this experiment based on this aim.
Worksheet 7
The Ozone Hole
The Electromagnetic Spectrum
Light is one example of electromagnetic radiation. Other examples include X-rays, ultraviolet (UV), infrared, TV waves, radio waves, and microwaves. All the energy that comes to us from the Sun comes in the form of electromagnetic radiation. Although these waves may seem to us to have different properties, to scientists they are all different versions of electromagnetic radiation, and they all have a number of important properties in common. For example, unlike sound waves, they can all travel through a vacuum, and they all travel through a vacuum with the same very high speed. This speed is 300 000 000 m s-1. Scientists have not found anything else that travels as fast as this. Even sound travels about one million times slower than light. On Earth, it is essential that we receive electromagnetic radiation from the Sun. Certainly, without the heat and light we receive, life as we know it could not exist. However, some other parts of the electromagnetic spectrum that we also receive from the Sun are harmful, not beneficial. For example, high UV radiation levels cause sunburn and skin cancer in humans and can also be damaging to other animals, plants and bacteria. We rely on our atmosphere to protect us from this radiation. In particular, we rely on a gas called ozone that is in the atmosphere.
Ozone gas consists of molecules of oxygen. However, each molecule contains three atoms of
oxygen. Normal molecules of oxygen
contain only two atoms of oxygen. Ozone
is actually poisonous. If it were found low in our atmosphere, it would be a
danger to life. However, it is found mostly between about 20 kilometres and 25
kilometres above the ground in the part of our atmosphere known as the
stratosphere. Only a very small part of
the atmosphere is made up from ozone, about 0.00004%. Luckily, even this very small amount of ozone is able to protect
life on Earth from the dangers of UV radiation. Ozone is formed from normal oxygen by the action of sunlight and
also by the action of lightning.
Actually, sunlight and lightning both create and destroy ozone: however,
normally the amount of ozone remains constant.
In 1985, British Antarctic Survey scientists reported that spring ozone levels had decreased by more than 30% over a ten-year period. Strangely enough, autumn ozone levels had stayed approximately the same. By 1993, spring ozone levels had plummeted to about 70% below the levels in the 1960s. Research found that chemicals called CFCs (chlorofluorocarbons) had been responsible for this rapid decline in ozone. These chemicals had been used in refrigerators, air-conditioners, plastic foams and aerosol sprays. About one million tonnes had been produced each year. CFCs are very stable compounds that can remain in the atmosphere for over 100 years. However, if they get into the stratosphere they can be broken down by UV radiation. When this happens they release free chlorine atoms that destroy the ozone. One free chlorine atom can destroy up to 100 000 ozone molecules. This research led to a worldwide agreement to ban CFCs. Ongoing studies have found that CFCs are not the only chemicals that can destroy ozone. It is important that we make sure that the chemicals that replace CFCs in our air-conditioning systems, refrigerators and so on are not harmful to the ozone layer.
The ozone hole begins to appear in spring for
two reasons. First, at this time the sunlight
is becoming stronger.
Through the autumn and the winter, chlorine molecules have been building up
in the stratosphere. The stronger sunlight in spring is able to convert these chlorine
molecules into free chlorine atoms.
Second, at this time there is a strong wind in the stratosphere
circulating around Antarctica. This strong circulating wind, called a vortex,
keeps the chlorine inside a region over the Antarctic continent. When this happens, it is possible that 70%
of the ozone layer can be destroyed in less than one month. In late spring the strong wind weakens and
allows ozone to come in from other parts of the stratosphere and so the hole
begins to fill up again. The Arctic is
affected much less in this way because no vortex forms. The process of ozone destruction is a
complicated one and is still only partly understood. However, it does seem that the very low temperatures in the
stratosphere above Antarctica do aid ozone destruction. Therefore Antarctica, being the coldest
place on Earth, is most likely to witness the greatest destruction of the ozone
layer. Such destruction is of
particular concern to people who live in countries near Antarctica, such as New
Zealand and Australia.
Problems Caused By The Ozone Hole
In spring, there is a huge reduction in the amount of ozone in the atmosphere above Antarctica. Luckily, the reduction in the ozone layer above more densely populated areas is not so large. However, scientists have calculated that even a small decrease of 2.5% in the ozone layer leads to a 4% increase in ultraviolet radiation, a 10% increase in skin cancer in humans, and a 2% increase in deaths from skin cancer. The increased UV radiation can also produce cataracts in the eyes of humans and animals.
Increased UV radiation also has an adverse effect on the ecosystem of marine life in the entire Southern Ocean. At the base of the food web there are extremely small plants called phytoplankton. During the brief Antarctic summer, these plants convert sunlight and chemicals into nourishment for themselves and other organisms in the food chain. The increased UV radiation has cut down the amount of nourishment the phytoplankton can produce by as much as 10%. This directly affects all organisms that feed on phytoplankton and, indirectly, all organisms in the food web.
Questions
1. List
seven examples of electromagnetic radiation.
State two properties that all seven examples have in common.
2.
State
two important differences between sound and light.
3. Oxygen
makes up about 20% of the Earth's atmosphere.
An oxygen molecule consists of two oxygen atoms. The chemical formula for this is 02. Copy the above information about oxygen into
your book. Write three similar
sentences about ozone.
4.