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Why does evaporation cause cooling?
When a liquid evaporates, its molecules convert from the liquid phase to the vapor phase and escape from the surface. What drives this process is heat. In order for the molecule to leave the liquid surface and escape as a vapor, it must take heat energy with it. The heat that it takes with it comes from the surface from which it evaporated. Since the molecule is taking heat with it as it's leaving, this has a cooling effect on the surface left behind.
The faster molecules, those with more energy, are more likely to escape. This means that the molecules still in a liquid state are the slower ones. The average speed of the remaining molecules is also slower. Thus the temperature of the remaining water is lower. That is why evaporation causes cooling.
When the wind blows on your finger, the hottest, highest-energy molecules evaporate. The water molecules remaining are slower-moving and less energetic. So
the molecules that are left result in a lower average energy, and
therefore a lower temperature. Your finger feels cooler in the
direction of the wind. That why evaporation causes cooling.
As the faster-moving molecules escape, the remaining molecules have lower average kinetic energy, and the temperature of the liquid thus decreases. This phenomenon is also called evaporative cooling.
This is why evaporating sweat cools the human body.
Why does evaporation take place on the surface of the water?
For molecules of a liquid to evaporate, they must be located near the surface, be moving in the proper direction, and have sufficient kinetic energy to overcome liquid-phase intermolecular forces
In an area of less pressure, evaporation happens faster because there is less exertion on the surface keeping the molecules from launching themselves.
Why does the temperature stay constant during freezing point?
The temperature stays constant while a liquid freezes because heat energy is released when the particles slow down to take up fixed and orderly position in the solid.
Why is it that the freezing and melting point of water is the same degrees?
We all know that the melting point of water is 0 °C (32 °F). The freezing point of water is the same as the melting point as ling as the water contains what is called a nucleating substance. , but in the absence of nucleators water can supercool to -42 °C (-43.6 °F) before freezing. It is difficult, if not impossible, to heat a solid above its melting point because the heat that enters the solid at its melting point is used to convert the solid into a liquid. It is possible, however, to cool some liquids to temperatures below their freezing points without forming a solid. When this is done, the liquid is said to be supercooled.
In the presence of nucleating substances, the freezing point of water is the same as the melting point, but in the absence of nucleators, water can supercool to −42 °C (−43.6 °F, 231 K) before freezing.
Science Report: The Leech
“Leeches are touted as ‘terrors of the jungle’,” my neighbour’s son told us after his army training in Brunei recently. His body has all the marks which he claimed are the “work of the leeches”. This prompts me to do a research on leeches.
There are about 650 species of leeches worldwide. Not all of them suck blood for sustenance. They can strike fear into the hearts of trekkers who invade their habitats. The leech analyses its environment with its impressive array of sensors for a good meal, in this case, animal and human blood. Some feed on worms, snails and insect larvae. Others are vegetarian and feed on organic debris.
I shall focus on leeches, which sucks blood as they hold many medicinal secrets, earning them the title of ‘physicians’. Since ancient times, leeches have been used in bloodletting by various civilizations. It was believed that certain health disorders were caused by bad blood, which could be removed by the leech.
Unfortunately, for the patient, bloodletting was supposed to be beneficial only when performed up to the point of fainting. Therefore, the patient might find himself plastered with up to fifty leeches, a feat certainly not for the faint hearted. A full meal for a leech only extracts about 5 millilitres but the resultant loss of blood from the wound can extend to 150millilitres. Modern science now utilized leeches in plastic surgery and reconstructive microsurgery involving the attachment or reattachment of body parts.
Leeches could alleviate venous congestion. True leeches have hind suckers for attaching themselves to the skin of their victims and a fore sucker for drawing blood. Aquatic leeches may feed on the blood on the blood of fishes, amphibians, birds or mammals, while land leeches only feed on the blood of mammals.
The feeding process is an art in efficiency. Unless disturbed, the leech can guzzle a few times its body weight of blood before dropping off and happily resting until its next meal in a few months time. Without the biochemical compounds secreted by the salivary glands during feeding, the leech will not survive successfully as humans and animals do not like to give up their blood. The first line of defence for the leech is stealth in the biochemical sense. The breach of the skin surface is almost painless (otherwise it will be a nightmare for a patient undergoing leech therapy). Thanks to an anaesthetic in the leech’s saliva, its blood sucking goes undetected. When we suffer a cut, we do not bleed to death because the blood clots. If left uninterrupted, blood can clot in about 10 minutes, presenting a major obstacle to the leech during feeding which may take about thirty minutes.
Therefore, a leech is armed with various countermeasures to disrupt this clotting process at a minimum of seven different points. Blood will continue to ooze from the biting site for a few hours even if the leech had his fill and ditched its host. This is made possible as the leech saliva has an anticoagulant (blood thinning agent), hirudin, which blocks thrombin, the enzyme initiating the clotting process.
So next time in the jungle, before you raise a hand to strike off this annoying pest, stop and ponder about the wondrous biochemical compounds in the leech, a veritable medicine packed in into a tiny critter. A wealth of medicinal secrets can hopefully be unraveled from further research and study by scientists. Or perhaps simply appreciate the leech for its remarkable methods of survival, forged from the crucible of evolution.

12. Mass, weight and density
Reflection on the lesson taught in Term 1. Any good suggestions to improve the lessons?
understood easily. But I feel that more time should be spent on doing experiments because I think that it will make us learn better as it is hands-on.
What I wish to learn in term 2
I wish to learn several topics such as:
Term 2
Reflection of term 2 test
I had noinsufficient time to it arrives. I hope that all of us can do much better in the term 3 test.
The things I learned in Term 2:
Basically, I learned the following:
and mixtures and the Periodic Table
2. Solutions and Suspensions (During home learning)
3. Separation techniques such as distillation, fractional distillation, evaporation to dryness, chromatography etc
4. States of matter
5. (solid, liquid and gas)
4. Kinetic theory of matter
5. Measurements
I learn how to plot graphs and how to operate a vernier caliper and micrometer and measure small things that our rulers can't measure.
Reflection on the lesson taught in Term 2. Any good suggestions to improve the lessons?
are quite boring.boring because and we were taking notes only. Half the class were either sleeping or not paying attention and were doing their own things. The lessons with the classclass. However, the lessons were valuable as there were only 2 science lessons a week and not taking notes only.we had to learn everything very quickly and complete the syllabus to take the test or else we would probably fail the test. Overall, I feel that term 2 is quite enjoyable. Although I feel that we should go on field trips to understand science better.
What I wish to learn in term 3
I wish to learn several topics such as:
-animals diet, behaviour etc
What improvement I would want to see in term 2:
so complacent. I will work harder and prepare more for the test. I will also pay more attention in class and try my best to talk less in class to not distract my classmate and the lesson as it would benefit everyone. I will also revise the notes and powerpoint slides given by the teacher and hand up my homework on time.
Term 3
Reflection on term 3 test
I had done quite well and had scored 80 for this test. The topics for the science test were Elements and Compounds, Solutions and Suspensions as well as Different Separation Techniques. These topics were taught either early in Term 3 or in Term 2. Therefore, I could easily revise through my notes for these 3 topics and memorize the important facts and important tips given by our science teacher . A very kind and thoughtful thing our Science teacher helped us to score higher was that she went through revision with the class before the Science Test. The period before that the science test was that the teacher did not come and Mrs Chu took advantage of the free period to go through the important stuff that would come out in the Test. That were very important and I could have scored higher because I did listen to what Mrs Chu was saying. If I had listened, I could have gotten much more than 80.
Topics we learn term 3
1. Separation techniques such as Filtration, Distillation, Sublimation and Paper Chromatography
2. Photosynthesis and respiration
3. Models and Systems (Cell structure, Functions of the different parts in a cell and Level of Organizations)
Reflection on the lesson taught in Term 2. Any good suggestions to improve the lessons?
I find the lessons very informative, interesting and interactive( hands-on). The Power Points posted in the IVLE are very comprehensive and easy to understand. There are also videos and plenty of graphics to help us understand the topic more. The experiments are also fun and interesting to carry out. We did some experiments on the topic "Cells" in the School Lab such as looking at animal and plant cells under a microscope. I had done this in Primary school but I could see the Plant and Animal Cells clearly under the microscope this time. We also learnt about the different parts of the cell, such as the Protoplasm and Mitochondria, Nucleus, Cell membrane, Cell wall, etc. I also learnt about the differences between an animal cell and a plant cell.
We were also taught the Level of Organisations. Many cells will make up a Tissue, many tissues working together will make an organ, many organs working together will form an organ system and lastly, many organ systems will form an organism!
However, sometimes the lesson can get a bit too boring and as it is the last lesson of the day. I think the lessons can improve if Mrs Chu perhaps shows us a bit more videos. I am sure that there are many science-related educational videos on Youtube. Another way to improve the lessons further is by organizing field trips for us to get close to Mother Nature.
What I wish to learn in Term 4
According to the Scheme Of Work, we will have a Science Trail in Term 4 as enrichment. I hope that this will be a fun experience for me and the whole class. I hope that we can go to the Science Centre and learn about science more deeply. I wish to learn more on biology too.
Improvement I would want to see in term 4
I would want to get a A1 for science like 80 and above ( I would try my best). I would revise for my test at an earlier date and not be so complacent. I hope I would be exempted.

My reflections:
I feel that this trip was helpful to me in a sense that it could widen my knowledge of things in the world.
if "disturbed". 1
1 kilogram is
Term 2
Reflection of term 2 test
-animals diet, behaviour etc
What improvement I would want to see in term 2:
be so complacentcomplacent.

At first, I did not know that Singapore had a 1kg metal hidden somewhere unknown. But I came to know about it after the trip. It is very important and is kept in a safe place as it would affect Singapore's standard 1kg if "disturbed". 1 kilogram is actually based on a piece of metal. Every fifty to one hundred years the metrology scientists will clean it and this causes the metal to be a bit lighter and this affects Singapore. The real metal piece is in France in some secret location and the world’s kilogram is based on that. The professors use calibration machines to synchronise the thermometers. I also managed to see a real laser and I was really surprised that the real laser is completely invisible!
Term 2
Reflection of term 2 test
I had done quite badly partly because I had no time to prepare for the measurements test and also because I made too many careless mistakes. I will not be so complacent in the future and will prepare for a science test a few weeks before it arrives.
The things I learned in Term 2:
Basically, I learned the following:
1. Elements, compounds and mixtures
2. Solutions and Suspensions
3. Separation techniques such as distillation, fractional distillation, evaporation to dryness, chromatography etc
4. States of matter
5. Kinetic theory of matter
Reflection on the lesson taught in Term 2. Any good suggestions to improve the lessons?
I feel that the lessons are quite boring. The lessons could be made more interesting by playing several science games with the class and not taking notes only.
What I wish to learn in term 3
I wish to learn several topics such as:
Models and Systems:
(Biology)
-Cell structure
-Function and organisation
-Digestive System
-Respiration
-Diffusion
-Osmosis
(Physics)
-Effects of heat
-Transfer of thermal energy
Advanced Chemistry:
-solubility graphs
Miscellaneous:
-animals diet, behaviour etc
What improvement I would want to see in term 2:
I would want to get a A1 for science like 80 and above ( I would try my best). I would revise for my test at an earlier date and not be so complacent

Welcome to my E-portfolio!

I feel that this trip was helpful to me in a sense that it could widen my knowledge of things in the world.
At first, I did not know that Singapore had a 1kg metal hidden somewhere unknown. But I came to know about it after the trip. It is very important and is kept in a safe place as it would affect Singapore's standard 1kg if "disturbed". 1 kilogram is actually based on a piece of metal. Every fifty to one hundred years the metrology scientists will clean it and this causes the metal to be a bit lighter and this affects Singapore. The real metal piece is in France in some secret location and the world’s kilogram is based on that. The professors use calibration machines to synchronise the thermometers. I also managed to see a real laser and I was really surprised that the real laser is completely invisible!
Term 2

Reflection on the lesson taught in Term 1. Any good suggestions to improve the lessons?
I feel that the lessons are quite interesting. The lessons are enriched and could be understood easily.
Field trips
I went to the metrology station on 9th March, 2010. I think that the trip was very meaningful and helpful to me.
What I learned:
I just found out that the word "metrology" means units of measurement. The metrology station has several laboratories: the mass and weight laboratory, the humidity laboratory, the thermometer laboratory and the laser laboratory. I will describe what I saw in each laboratory and show you some pictures I took during the trip.
The mass and weight laboratory
{Image(108).jpg} This is a normal weighing scale. basically, if we want to measure the mass of an item, just place it on thee weighing scale.
{Image(107).jpg} This is a vacuum weighing machine. However, the professor did not demonstrate how it works for safety reasons.
{Image(105).jpg} This is an ancient weighing balance. I shall explain how it works. For example, if we want to find out which item is heavier, we put both items on the metal plate. The item that is heavier will go downwards and the lighter item item will go upwards.
{Image(109).jpg} This is a poster about primary mass standards. I heard from the professor that there is a 1kg metal hidden and locked somewhere secret in the metrology station. The reason why is because this will affect the Singapore's standard 1kg.
The humidity laboratory
{Image(116).jpg} This is a hygrometer used to measure the humidity in the air.
{Image(115).jpg} This is a two-pressure humidity generator to calibrate a hygrometer which are instruments used to measure the relative humidity in the air.
{Image(114).jpg} This is a poster about the two pressure humidity generator.
The thermometer laboratory
{Image(120).jpg} This a "no contact" thermometer. How does it work? Just please down the trigger and direct the red light on your forehead, then the thermometer will receive the data(your current temperature).
{Image(117).jpg}
This is a calibration process. The thermometer is turned on and it will measure the temperature of the hot water. The temperature of the hot water is taken down. Then a machine is turned on and it will measure the temperature of the water by putting a heat sensor into the water. Then a comparison is made between the two temperatures. If the temperature matched, the thermometer is accurate. If the temperature does not match, then the professors have to adjust the thermometer.
{Image(118).jpg} This is the machine with the heat sensor.
{Image(122).jpg} This is a calibration machine for the infrared ear thermometer.
The laser laboratory
{Image(110).jpg}
There are several lasers and mirrors on this platform. The mirrors will reflect the laser light into a light sensor and the light sensor will measure the intensity of the light and transfer the data into a computer.
{Image(112).jpg} This is a laser generator. The laser is generated bu fuel. Fuel produces electricity and electricity produces light.
My reflections:
I feel that this trip was helpful to me in a sense that it could widen my knowledge about how things work
What I wish to learn in term 2
I wish to learn several topics such as:
What improvement I would want to see in term 2:
I would want to get a higher A1 for science like 90 and above for all tests( I would try my best). I would widen my knowledge by reading more science magazines and pay attention in class.
Field trips
I went to the metrology station on 9th March, 2010. I think that the trip was very meaningful and helpful to me.
What I learned:
I just found out that the word "metrology" means units of measurement. The metrology station has several laboratories: the mass and weight laboratory, the humidity laboratory, the thermometer laboratory and the laser laboratory. I will describe what I saw in each laboratory and show you some pictures I took during the trip.
The mass and weight laboratory
{Image(108).jpg} This is a normal weighing scale. Basically, if we want to measure the mass of an item, just place it on thee weighing scale.
{Image(107).jpg} This is a vacuum weighing machine. However, the professor did not demonstrate how it works for safety reasons.
{Image(105).jpg} This is an ancient weighing balance. I shall explain how it works. For example, if we want to find out which item is heavier, we put both items on the metal plate. The item that is heavier will go downwards and the lighter item item will go upwards.
{Image(109).jpg} This is a poster about primary mass standards. I heard from the professor that there is a 1kg metal hidden and locked somewhere secret in the metrology station. The reason why is because this will affect the Singapore's standard 1kg.
The humidity laboratory
{Image(116).jpg} This is a hygrometer used to measure the humidity in the air.
{Image(115).jpg} This is a two-pressure humidity generator to calibrate a hygrometer which are instruments used to measure the relative humidity in the air.
{Image(114).jpg} This is a poster about the two pressure humidity generator.
The thermometer laboratory
{Image(120).jpg} This a "no contact" thermometer. How does it work? Just please down the trigger and direct the red light on your forehead, then the thermometer will receive the data(your current temperature).
{Image(117).jpg}
This is a calibration process. The thermometer is turned on and it will measure the temperature of the hot water. The temperature of the hot water is taken down. Then a machine is turned on and it will measure the temperature of the water by putting a heat sensor into the water. Then a comparison is made between the two temperatures. If the temperature matched, the thermometer is accurate. If the temperature does not match, then the professors have to adjust the thermometer.
{Image(118).jpg} This is the machine with the heat sensor.
{Image(122).jpg} This is a calibration machine for the infrared ear thermometer.
The laser laboratory
{Image(110).jpg}
There are several lasers and mirrors on this platform. The mirrors will reflect the laser light into a light sensor and the light sensor will measure the intensity of the light and transfer the data into a computer.
{Image(112).jpg} This is a laser generator. The laser is generated bu fuel. Fuel produces electricity and electricity produces light.
My reflections:
I feel that this trip was helpful to me in a sense that it could widen my knowledge of things in the world.
At first, I did not know that Singapore had a 1kg metal hidden somewhere unknown. But I came to know about it after the trip. It is very important and is kept in a safe place as it would affect Singapore's standard 1kg if "disturbed". 1 kilogram is actually based on a piece of metal. Every fifty to one hundred years the metrology scientists will clean it and this causes the metal to be a bit lighter and this affects Singapore. The real metal piece is in France in some secret location and the world’s kilogram is based on that. The professors use calibration machines to synchronise the thermometers. I also managed to see a real laser and I was really surprised that the real laser is completely invisible!

There are several lasers and mirrors on this platform. The mirrors will reflect the laser light into a light sensor and the light sensor will measure the intensity of the light and transfer the data into a computer.
{Image(112).jpg} This is a laser generator. The laser is generated bu fuel. Fuel produces electricity and electricity produces light.
My reflections:
I feel that this trip was helpful to me in a sense that it could widen my knowledge about how things work
What I wish to learn in term 2
I wish to learn several topics such as:
-how to draw a solubility graph and interpret it
-separation techniques such as filtration, distillation and chromatography
Biology:
-about leeches
-about endangered animals and their diet, behaviour
Miscellaneous:
-earth facts
-biofuels
-water facts
-NEWater
What improvement I would want to see in term 2:
my best). I would widen my knowledge by reading more science magazines and pay attention in class.

{Image(109).jpg} This is a poster about primary mass standards. I heard from the professor that there is a 1kg metal hidden and locked somewhere secret in the metrology station. The reason why is because this will affect the Singapore's standard 1kg.
The humidity laboratory
{Image(116).jpg} This is a hygrometer used to measure the humidity in the air.
{Image(115).jpg} This is a two-pressure humidity generator to calibrate a hygrometer which are instruments used to measure the relative humidity in the air.
{Image(114).jpg} This is a poster about the two pressure humidity generator.
The thermometer laboratory
{Image(120).jpg} This a "no contact" thermometer. How does it work? Just please down the trigger and direct the red light on your forehead, then the thermometer will receive the data(your current temperature).
{Image(117).jpg}
This is a calibration process. The thermometer is turned on and it will measure the temperature of the hot water. The temperature of the hot water is taken down. Then a machine is turned on and it will measure the temperature of the water by putting a heat sensor into the water. Then a comparison is made between the two temperatures. If the temperature matched, the thermometer is accurate. If the temperature does not match, then the professors have to adjust the thermometer.
{Image(118).jpg} This is the machine with the heat sensor.
{Image(122).jpg} This is a calibration machine for the infrared ear thermometer.
The laser laboratory
{Image(110).jpg}
There are several lasers and mirrors on this platform. The mirrors will reflect the laser light into a light sensor and the light sensor will measure the intensity of the light and transfer the data into a computer.
{Image(112).jpg} This is a laser generator. The laser is generated bu fuel. Fuel produces electricity and electricity produces light.
What I wish to learn in term 2
I wish to learn several topics such as: