Tuesday, October 27, 2009

Green House Effect

INTRODUCTION

Greenhouse Effect, the capacity of certain gases in the atmosphere to trap heat emitted from the Earth’s surface, thereby insulating and warming the Earth. Without the thermal blanketing of the natural greenhouse effect, the Earth’s climate would be about 33 Celsius degrees (about 59 Fahrenheit degrees) cooler—too cold for most living organisms to survive.

The greenhouse effect has warmed the Earth for over 4 billion years. Now scientists are growing increasingly concerned that human activities may be modifying this natural process, with potentially dangerous consequences. Since the advent of the Industrial Revolution in the 1700s, humans have devised many inventions that burn fossil fuels such as coal, oil, and natural gas. Burning these fossil fuels, as well as other activities such as clearing land for agriculture or urban settlements, releases some of the same gases that trap heat in the atmosphere, including carbon dioxide, methane, and nitrous oxide. These atmospheric gases have risen to levels higher than at any time in the last 420,000 years. As these gases build up in the atmosphere, they trap more heat near the Earth’s surface, causing Earth’s climate to become warmer than it would naturally.



HOW THE GREENHOUSE EFFECT WORKS

The greenhouse effect results from the interaction between sunlight and the layer of greenhouse gases in the Earth's atmosphere that extends up to 100 km (60 mi) above Earth's surface. Sunlight is composed of a range of radiant energies known as the solar spectrum, which includes visible light, infrared light, gamma rays, X rays, and ultraviolet light. When the Sun’s radiation reaches the Earth’s atmosphere, some 25 percent of the energy is reflected back into space by clouds and other atmospheric particles. About 20 percent is absorbed in the atmosphere. For instance, gas molecules in the uppermost layers of the atmosphere absorb the Sun’s gamma rays and X rays. The Sun’s ultraviolet radiation is absorbed by the ozone layer, located 19 to 48 km (12 to 30 mi) above the Earth’s surface.
About 50 percent of the Sun’s energy, largely in the form of visible light, passes through the atmosphere to reach the Earth’s surface. Soils, plants, and oceans on the Earth’s surface absorb about 85 percent of this heat energy, while the rest is reflected back into the atmosphere—most effectively by reflective surfaces such as snow, ice, and sandy deserts. In addition, some of the Sun’s radiation that is absorbed by the Earth’s surface becomes heat energy in the form of long-wave infrared radiation, and this energy is released back into the atmosphere.
Certain gases in the atmosphere, including water vapor, carbon dioxide, methane, and nitrous oxide, absorb this infrared radiant heat, temporarily preventing it from dispersing into space. As these atmospheric gases warm, they in turn emit infrared radiation in all directions. Some of this heat returns back to Earth to further warm the surface in what is known as the greenhouse effect, and some of this heat is eventually released to space. This heat transfer creates equilibrium between the total amount of heat that reaches the Earth from the Sun and the amount of heat that the Earth radiates out into space. This equilibrium or energy balance—the exchange of energy between the Earth’s surface, atmosphere, and space—is important to maintain a climate that can support a wide variety of life.


TYPES OF GREENHOUSE GASES

Earth’s atmosphere is primarily composed of nitrogen (78 percent) and oxygen (21 percent). These two most common atmospheric gases have chemical structures that restrict absorption of infrared energy. Only the few greenhouse gases, which make up less than 1 percent of the atmosphere, offer the Earth any insulation. Greenhouse gases occur naturally or are manufactured. The most abundant naturally occurring greenhouse gas is water vapor, followed by carbon dioxide, methane, and nitrous oxide. Human-made chemicals that act as greenhouse gases include chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs).
Since the 1700s, human activities have substantially increased the levels of greenhouse gases in the atmosphere. Scientists are concerned that expected increases in the concentrations of greenhouse gases will powerfully enhance the atmosphere’s capacity to retain infrared radiation, leading to an artificial warming of the Earth’s surface.
-Water Vapor
Water vapor is the most common greenhouse gas in the atmosphere, accounting for about 60 to 70 percent of the natural greenhouse effect. Humans do not have a significant direct impact on water vapor levels in the atmosphere. However, as human activities increase the concentration of other greenhouse gases in the atmosphere (producing warmer temperatures on Earth), the evaporation of oceans, lakes, and rivers, as well as water evaporation from plants, increase and raise the amount of water vapor in the atmosphere.

-Carbon Dioxide
Carbon dioxide constantly circulates in the environment through a variety of natural processes known as the carbon cycle. Volcanic eruptions and the decay of plant and animal matter both release carbon dioxide into the atmosphere. In respiration, animals break down food to release the energy required to build and maintain cellular activity. A byproduct of respiration is the formation of carbon dioxide, which is exhaled from animals into the environment. Oceans, lakes, and rivers absorb carbon dioxide from the atmosphere. Through photosynthesis, plants collect carbon dioxide and use it to make their own food, in the process incorporating carbon into new plant tissue and releasing oxygen to the environment as a byproduct.
In order to provide energy to heat buildings, power automobiles, and fuel electricity-producing power plants, humans burn objects that contain carbon, such as the fossil fuels oil, coal, and natural gas; wood or wood products; and some solid wastes. When these products are burned, they release carbon dioxide into the air. In addition, humans cut down huge tracts of trees for lumber or to clear land for farming or building. This process, known as deforestation, can both release the carbon stored in trees and significantly reduce the number of trees available to absorb carbon dioxide.
As a result of these human activities, carbon dioxide in the atmosphere is accumulating faster than the Earth’s natural processes can absorb the gas. By analyzing air bubbles trapped in glacier ice that is many centuries old, scientists have determined that carbon dioxide levels in the atmosphere have risen by 31 percent since 1750. And since carbon dioxide increases can remain in the atmosphere for centuries, scientists expect these concentrations to double or triple in the next century if current trends continue.

The concentration of carbon dioxide in the atmosphere



-Methane
Many natural processes produce methane, also known as natural gas. Decomposition of carbon-containing substances found in oxygen-free environments, such as wastes in landfills, release methane. Ruminating animals such as cattle and sheep belch methane into the air as a byproduct of digestion. Microorganisms that live in damp soils, such as rice fields, produce methane when they break down organic matter. Methane is also emitted during coal mining and the production and transport of other fossil fuels.
Methane has more than doubled in the atmosphere since 1750, and could double again in the next century. Atmospheric concentrations of methane are far less than carbon dioxide, and methane only stays in the atmosphere for a decade or so. But scientists consider methane an extremely effective heat-trapping gas—one molecule of methane is 20 times more efficient at trapping infrared radiation radiated from the Earth’s surface than a molecule of carbon dioxide.

-Nitrous Oxide

Nitrous oxide is released by the burning of fossil fuels, and automobile exhaust is a large source of this gas. In addition, many farmers use nitrogen-containing fertilizers to provide nutrients to their crops. When these fertilizers break down in the soil, they emit nitrous oxide into the air. Plowing fields also releases nitrous oxide.
Since 1750 nitrous oxide has risen by 17 percent in the atmosphere. Although this increase is smaller than for the other greenhouse gases, nitrous oxide traps heat about 300 times more effectively than carbon dioxide and can stay in the atmosphere for a century.

-Fluorinated Compounds
Some of the most potent greenhouse gases emitted are produced solely by human activities. Fluorinated compounds, including CFCs, HCFCs, and HFCs, are used in a variety of manufacturing processes. For each of these synthetic compounds, one molecule is several thousand times more effective in trapping heat than a single molecule of carbon dioxide.
CFCs, first synthesized in 1928, were widely used in the manufacture of aerosol sprays, blowing agents for foams and packing materials, as solvents, and as refrigerants. Nontoxic and safe to use in most applications, CFCs are harmless in the lower atmosphere. However, in the upper atmosphere, ultraviolet radiation breaks down CFCs, releasing chlorine into the atmosphere. In the mid-1970s, scientists began observing that higher concentrations of chlorine were destroying the ozone layer in the upper atmosphere. Ozone protects the Earth from harmful ultraviolet radiation, which can cause cancer and other damage to plants and animals. Beginning in 1987 with the Montréal Protocol on Substances that Deplete the Ozone Layer, representatives from 47 countries established control measures that limited the consumption of CFCs. By 1992 the Montréal Protocol was amended to completely ban the manufacture and use of CFCs worldwide, except in certain developing countries and for use in special medical processes such as asthma inhalers.
Scientists devised substitutes for CFCs, developing HCFCs and HFCs. Since HCFCs still release ozone-destroying chlorine in the atmosphere, production of this chemical will be phased out by the year 2030, providing scientists some time to develop a new generation of safer, effective chemicals. HFCs, which do not contain chlorine and only remain in the atmosphere for a short time, are now considered the most effective and safest substitute for CFCs.
-Other Synthetic Chemicals
Experts are concerned about other industrial chemicals that may have heat-trapping abilities. In 2000 scientists observed rising concentrations of a previously unreported compound called trifluoromethyl sulphur pentafluoride. Although present in extremely low concentrations in the environment, the gas still poses a significant threat because it traps heat more effectively than all other known greenhouse gases. The exact sources of the gas, undisputedly produced from industrial processes, still remain uncertain.


THINNING OF OZONE LAYER

The main cause of ozone layer depletion is the increasing level of chlorofluorocarbons (CFCs) in the atmosphere.
• The use of CFCs as coolants in air conditioners and refrigerators, as propellants in aerosol cans, as solvents in the electronics industry and as foaming agents in the making of polystyrene boxes has released large amounts of CFCs into the atmosphere.
• CFCs are unreactive and can remain unchanged for over 100 years.
• UV radiation breaks down CFCs releasing chlorine radicals which destroy ozone in a chain reaction.
• it is estimated that a single chlorine atom can destroy 100thousand molecules of ozone in a year.




IMPACT OF THINNING OF THE OZONE LAYER AND
GLOBAL WARMING ON THE ECOSYSTEM


As the concentration of greenhouse gases rises, the greenhouse effect become more pronounced. As more heat is trapped in the atmosphere, the Earth’s average temperature rises. This is known as global warming.

Global warming and the thinning of the ozone layer both have an enormous impact on the ecosystem. The average increase in the Earth’s temperature could change weather pattern and agricultural output. There us also convincing evidence from research carried out by scientists that links the melting of the polar ice caps to global warming. This in turn leads to a corresponding rise in sea level.

By absorbing most of the ultraviolet radiation, the ozone layer shields living organisms on Earth from the damaging effects of ultraviolet radiation. The consequences of the thinning of the ozone layer can be quite severe. The incidence of skin cancer and cataracts among the population will be on increase.



EFFORTS TO CONTROL GREENHOUSE GASES
Due to overwhelming scientific evidence and growing political interest, global warming is currently recognized as an important national and international issue. Since 1992 representatives from over 160 countries have met regularly to discuss how to reduce worldwide greenhouse gas emissions. In 1997 representatives met in Kyôto, Japan, and produced an agreement, known as the Kyôto Protocol, which requires industrialized countries to reduce their emissions by 2012 to an average of 5 percent below 1990 levels. To help countries meet this agreement cost-effectively, negotiators are trying to develop a system in which nations that have no obligations or that have successfully met their reduced emissions obligations could profit by selling or trading their extra emissions quotas to other countries that are struggling to reduce their emissions. Negotiating such detailed emissions trading rules has been a contentious task for the world community since the signing of the Kyôto Protocol. A ratified agreement is still not yet in force, and ratification received a setback in 2001 when newly elected U.S. president George W. Bush renounced the treaty on the grounds that the required carbon-dioxide reductions in the United States would be too costly. He also objected that developing nations would not be bound by similar carbon-dioxide reducing obligations. However, many experts expect that as the scientific evidence about the dangers of global warming continues to mount, nations will be motivated to cooperate more effectively to reduce the risks of climate change.

Monday, October 26, 2009

Aquatic Adaptation

Aquatic plants - also called hydrophytic plants or hydrophytes - are plants that have adapted to living in aquatic environments.

One of the main problems facing submerged aquatic plants is their inability to obtain oxygen. Unlike terrestrial plants, these plants cannot obtain the vital gas through their stomata because they are submerged in water.

Therefore, the stems, roots, and leaves of submerged aquatic plants posses aerenchyma cells, which supply oxygen to the rest of the plants.

Aerenchyma is a parenchyma tissue with large intercellular air spaces. It stores and transports oxygen to living tissues.

Air spaces within the tissues help to keep the aquatic plant buoyant so that its leaves can reach the top of the pond, thus maximising the amount of sunlight it receives.

Submerged aquatic plants utilise living in water to their fullest advantage. Since these plants are in no danger of drying out, the leaves have few or no cuticles on the surface of their leaves.

In addition, the stems of these plants are limp and delicate with little strengthening tissue because they utilise the water for support.

The leaves tend to be thin, flexible and narrow. These finely dissected leaves offer little resistance to running water and can be dragged through the water without tearing.

*******
Characteristics of hydrophytes:
  1. A thin cuticle. Cuticles primarily prevent water loss, thus most hydrophytes have no need for cuticles.
  2. Stomata that are open most of time because water is abundant and therefore there is no need for it to be retained in the plant. This means that guard cells on the stomata are generally inactive.
  3. An increased number of stomata, that can be on either side of leaves.
  4. A less rigid structure: water pressure supports them.
  5. Flat leaves on surface plants for floatation.
  6. Air sacs for floatation.
  7. Smaller roots: water can diffuse directly into leaves.
  8. Feathery roots: no need to support the plant.
  9. Specialized roots able to take in oxygen.
For example, some species of buttercup (genus Ranunculus) float slightly submerged in water; only the flowers extend above the water. Their leaves and roots are long and thin and almost hair-like; this helps spread the mass of the plant over a wide area, making it more buoyant. Long roots and thin leaves also provide a greater surface area for uptake of mineral solutes and oxygen.

Wide flat leaves in water lilies (family Nymphaeaceae) help distribute weight over a large area, thus helping them float near surface.

Many fish keepers keep aquatic plants in their tanks to control phytoplankton and moss by removing metabolites.

Many species of aquatic plant are invasive species in different parts of the world. Aquatic plants make particularly good weeds because they reproduce vegetatively from fragments.

Radioactive - The Brighter Side

Radioactive substances can be useful. In fact, some of them are used in fields like medicine, agriculture and archaelogy.

Tracers
  • In the medical field, the radioactive iodine-131, whose pathway can be traced, is injected into patients with thyroid gland dysfunction to check the function of the glands and detect the growth of tumours.
  • To trace water leakages underground, radioactive substances are introduced into water pipelines. When there is a water leakage, radioactive detectors such as Geiger-Muller counter will provide radioactive readings.

Sterilisers
  • Gamma rays are used to sterilise medical instruments to prevent contamination. In the food industry, they are used to prevent decay of food so that the food can last longer and be exported. In agricultural field, gamma rays are used to sterilise pests.

Nuclear reactors
  • In a nuclear reactor, radioactive substances decay and give out a great amount of energy, which is used as an electrical energy source. However, this type of energy is expensive.

Nuclear energy
  • Nuclear energy is derived from the nucleus of a substance. Nuclear energy can be produced by fusion (joining two nuclei of atoms to form a heavier nucleus) or fission (splitting the nucleus into two smaller and lighter nuclei, and releasing one or more neutrons).

Aktiviti Dalam Makmal Biologi

Beberapa bulan lepas, pelajar Tingkatan 4Gemilang telah menjalankan satu kajian untuk mengkaji sistem pernafasan seekor katak.. Pelajar tingkatan 5Gemilang turun menjalankan kajian tersebut oleh kerana tidak berpeluang menjalankan kajian ini pada tahun lepas..respiratory system of a frog
hasil kajian yang telah dijalankan adalah seperti rajah di atas..↑

Berikut adalah gambar-gambar semasa mereka menjalankan kajian tersebut.
Pelajar-pelajar 4Gemilang
Katak experiment.

bakal-bakal doktor...
tekun kak najibah ni....
Bila doktor bertemu doktor.....
bakal doktor haiwan yang berjaya...^_^


tamat sudah riwayat seekor katak...


pelajar-pelajar 5Gemilang

keciknya katak!!

potong..potong..cik dah potong?

hancur katak tu dikerjakan...

kejayaan besar...

berusaha gigih...

mangsa keadaan...





click here for more information about frog..

Sunday, October 25, 2009

Wonderful Salt

Life without salt would be more than bland.

Salt either comes from evaporating seawater or is mined.

Most salt fields (spots of very salty water) are near the ocean. Nearby salt fields include those in Kampot, Cambodia an Nha Trang, Vietnam.

There are salt mines all over the world where people mine for rock salt. These mines are dried-up lakes and oceans. As the salty waters become enclosed or buried, the salt in the water turns into solid layers.

In the past, salt was so precious that salt roads were made, mostly to enable the transportation of salt to cities where there were no salt lakes or nearby seashores.

In certain cultures, salt was sacrificed to the gods. It was considered to have magical powers, too. Doctors would sprinkle wounds with salt in the hope of fighting off infection.

Today, say is sold in every shop and supermarket, and is more than a seasoning. Salt is used to make leather, roads, soap, glass, chlorine and paper.

It is also used to preserve hay and food, purify and soften water, refine metals, melt snow and ice, and freeze ice cream.

Salt is useful stuff, indeed!

Scientific Investigation

Learning Objective - Applying Scientific Investigation
Learning Outcomes - A student is able to:
  1. identify variables in a given situation,
  2. identify the relationship between two variables to form a hypothesis,
  3. design and carry out a simple experiment to test the hypothesis,
  4. record and present data in a suitable form,
  5. interpret data to draw conclusions,
  6. write a report on an experiment,
  7. practise scientific attitudes and noble values.

Scientific Investigation / Scientific Method


Gambar hanyalah hiasan

Scientific method is a body of technique of acquiring knowledge about the nature and its phenomena.

Basics Steps of Scientific Investigation

1. Identifying problem
2. Making hypothesis
3. Planning the investigation
4. Identifying and Controlling Variable
5. Conducting the experiment
6. Collecting and recording data
7. Analysing and interpreting data
8. Making conclusion
9. Preparing the report

Objective :
  • State the aim of the experiment.
Problem Statement :
  • Pose questions about the observations made.
Hypothesis :
  • Formulate a possible explanation or prediction based on the observations
# Hypothesis is a suggested explanation for a specific phenomenon.

Variables :
  • Identify and control the manipulated, responding and fixed (controlled) variables.
# Variable is a quantity whose value may change in an experiment. It is the parameter that may influence the outcome of an experiment or the data been collected in the experiment.

Materials & Apparatus :
  • List the materials and apparatus which will be and used during the experiment.


Technique :
  • State the technique involved in obtaining the results.


Gambar hanyalah hiasan

Procedure :

  1. Write the instructions to carry out the experiment.
  2. The procedures should be written using reported speech. For example, 'Examine the slide under the microscope' should be written as 'The slide is examined under the microscope'.
  3. Diagrams can be drawn to show the set-up of the experiment. They should be simple and two-dimensional. The apparatus should be drawn with a clear outline and labelled accordingly

Gambar hanyalah hiasan

Results :
  • Present the results in the form of simple diagrams, charts, graphs or tables. Include calculations where necessary.

Discussion :
  • Discuss, analyse and intepret the data obtained, then determine the relationship between the manipulated

Conclusion :
  • Draw a conclusion based on the hypothesis given earlier.

Thursday, September 10, 2009

►INTRODUCTION◄

The Malaysian science curriculum comprises three core science subjects and four elective science subject. The core subjects are science at primary school lever, science at lower secondary school level and science at upper secondary school level. Elective science subjects offered up the upper secondary levels are and consist biology, chemistry, physics and additional science. The core science subjects for the primary and lower secondary level are designed to provide students with basic science knowledge, prepare students to be literate in science and enable students to continue their science education upper at secondary level. Core science at upper secondary levels is designed to produce students who are literate in science, innovative, and able to apply scientific knowledge in decision-making and problem solving in everyday life. The elective science subjects prepare students who are more science subjects prepare students who are more scientifically inclined to pursue the study of science at post-secondary level. This group of students would take up careers in the field of science and technology and play a leading role in this field for national.





AIM

The aims of the physics curriculum for secondary school are to provide students with the knowledge and skills of science and technology and enable them to solve problems and make decisions in everyday life based on scientific attitudes and noble values.





Objective


The Biology curriculum for secondary school enables students to :

- acquire knowledge in Biology in the everyday life experiences
- understand developments in the field of Biology
- acquire scientific and thinking skill
- apply knowledge and skill in a creative and critical manner for problem solving and decision making.
- Evaluate Biology information wisely and effectively.
- Practice and internalize scientific attitudes and good moral.
- Appreciate the contributions of Biology towards national development and the well-being of mankind.
- Realise that scientific discoveries are the result of human endeavour to the best of his or her intellectual and mental capabilities to understand natural phenomena for the betterment of mankind.
- Be aware of the need to love and care for the environment and play an active role in its preservation and conservation