2008 Gr 11 Biology Field Trip

In September the Gr 11 Biology classes completed a week long field course on Tioman Island. Here they had the opportunity to extend their study of ecology by applying their knowledge to field work on the island. The students studied the coral reef, mangrove, rocky shore and rainforest ecosystems in depth. They completed two major pieces of research which will form part of their Internal Assessment portfolio of work for their IB Diploma.


It was a fantastic week as the photos below show........

Grade 8 WASTE PLASTICS PROJECT

Our class, Ms Carter’s Gr 8 Science class, did a “Waste Plastics Project”. For a week, we had to collect plastics that we were going to throw away and bring them to class. The day we chose to do our tally was on Wednesday, 20/08/2008.

We left all our plastics in a corner of the science lab, and they piled up into a heap as big as a mountain!
Items collected included plastic bottles, containers, snack wrappers, plastic bags and so on. With the help of our fellow classmates, we separated all the collected items
into different categories, and placed them around the lab accordingly.

By the end of the categorizing, there were massive piles of plastic items spread across the desks. Who would have guessed that just twenty families had already amassed such a large amount of plastic waste in just a week?! Imagine just how much more plastic would have been wasted across Singapore!!

TABLE TO SHOW WASTE PLASTICS COLLECTED:




As you can see from the results of our “WASTE PLASTICS PROJECT”, the amount of plastic that is wasted is huge and should be seen as a GREAT cause for concern!

Here are a few ways YOU can help cut down on the amount of waste plastic without drastically altering your lifestyle:

1) When you get takeaway from hawker centres, the vendor will usually pack your food in plastic containers. The next time you get food from the hawker centre, you should bring along the plastic containers you received the last time and ask the vendors to put your food in those you brought instead of giving you more.

2) The next time you go grocery shopping, bring along an eco-friendly cloth bag or a rucksack to put your groceries in, instead of using plastic bags.

3) If you get drinks in plastic bottles, you should reuse those plastic
bottles as your drinking bottles or throw them in the recycling bin.

But the easiest way to cut down on buying drinks packed in plastic bottles is simply not to buy them! Besides, those drinks are nothing but sugar and completely unnecessary anyway!

4) DO NOT USE PLASTIC UTENSILS. Use steel utensils instead.

Now, you have no excuse to waste plastic ever again!

Did you know…??
* Singapore’s landfill sites are located at Ulu Pandan, Pulau Semakau, Senoko, Tuas and Tuas South.

* One of Singapore’s landfill sites, Tuas South, is one of the largest in the world.
Plastic cannot biodegrade. Plastic waste thus takes up a lot of landfill space.

* Pulau Semakau (Singapore’s newest landfill site) is expected to last until 2030 – only slightly over twenty years from now. However, if the amount of waste produced in Singapore continues to rise, the lifespan of the Pulau Semakau landfill might be shorter than expected.

Chlorophyll and Starch in Leaves

On the 24/7/08, Tuesday. Our Grade 10 FIB class, 10RRa learnt a new topic for biology lesson, photosynthesis. To allow us to have a better understanding of how photosynthesis occurs, Dr Hjorth engaged us in an experiment which requires us to test for starch in a piece of leaf.

Our class was then divided into several groups. Whereby we then obtained leaves from various plants and begin on our experiment.
Our group consisted of Yvette, Nicole and Sunshine. Dr Hjorth gave us a piece of leaf that looked distinctively different from the ordinary green leaves. The colour of the leaf was as of such, from the centre, pink, pale yellow, to the edges which are green. According to our knowledge, only the green parts of the leaves contain starch. Yet now we have a leaf with 3 shades, would the coloured parts possibly test positive to starch?

Step 1: First we had to place the leaf in boiling water for a minute to soften it.

Step 2: Once that is done, we place the leaf into a new test-tube with ethanol. Stand the test-tube in a beaker of hot water for around 10 minutes.

Step 3: Wash the leaf in cold water

Step 4: Spread the leaf flat on the Petri dish and cover it with iodine solution. If the leaf turns blue-black, it means starch is present.

After conducting the required steps, we obtained the following results:



As you can see, the places which were green turned blue-black, indicating starch was present where chlorophyll was. The pale coloured parts of the leaf stayed the colour they were, indicating starch was absent. So we can conlude that chlorophyll is involved in photosynthesis producing starch. The reason why a substance like starch is used for storage in plants is because it is insoluble, and does not cause problems like osmosis, unlike glucose.

Making a DNA model!

Constructing a DNA modelThe FIB 10JGo class constructed a DNA model that could be stretched from the third storey in our school all the way down to the first storey, almost touching the ground (see photo below). For the construction, we made about 200 small circular phosphate molecules, 200 pentagonal sugar molecules and 400 rectangular base molecules!!

It was a fun and lively activity, but we did learn a lot about DNA. Or at least, we could cope well with Ms. Carter’s questions afterwards.
DNA stands for deoxyribonucleic acid. We are familiar with DNA in relation to inheritance. For example, we know that DNA has something to do to why offspring often have their parents’ characteristics. Well, that’s correct because DNA is a nucleic acid molecule that carries genetic instructions that is found in all living organisms except some viruses.
In cells of eukaryotic organisms (which have a nucleus in their cells), DNA is found inside the nucleus. Animals (humans are included here), plants, fungi and protists are eukaryotes, so they have their DNA inside their nucleus. Since bacteria do not have a nucleus, they are prokaryotes and their DNA is found in cytoplasm.Now, look at the photo below. It’s a close-up look at our DNA model. The colourful rectangles represent base molecules and contain either one of these letters: T, A, G or C. T stands for thymine, A for adenine, G for guanine and C for cytosine. Notice that T only pairs up with A and G with C. This is the rule of base pairing, i.e. the bases will always pair up this way. Each pair of bases is held together by hydrogen bonds (see the staple between two bases).

The DNA model above looks like a ladder. The phosphates (represented by the yellow circles) join up with sugar molecules (the pentagons) and they make up the uprights of the ladder; the bases make up the rungs. We further twisted the model above into a beautiful double helix (the molecular structure of an actual DNA molecule), so it looked like a spiral staircase.


Petrus Bosa Layarda

Year 9 research: Cutting edge applications of nanotechnology

Diamond and graphite are two well-known forms of carbon. In 1985 scientists discovered a third form of carbon based on 60 atoms bonded in a football-like structure. Scientists called this 'buckminsterfullerene', or 'buckyball'. This started a search for other carbon structures. In 1991 a Japanese scientist called Sumio Iijima found carbon nanotubes. These are about 10 000 times thinner than a human hair, made from carbon atoms bonded in sheets and rolled into tubes. Scientists are working to find out more about carbon nanotubes and what they could be used for.

What do nanotubes look like?

Images Top to bottom: carbon nanotubes, a colored image of a nanotube, a ‘buckyball’

Year 9 have been researching the current applications of nanotubes and other areas of nanotechnology - the science of building machines at sub-atomic level.

Scott Heng, Paul Wong, Scott Lim and Qin Yi researched the most recent applications of nano-tubes and discovered that they are 50 times stronger than steel and are currently being developed as molecular sized wires in electronic circuitry. They explained how these molecular sized nano-wires are currently being developed to produce miniature gadgets.

Maria, Antonia and Nicole discovered that a microscopic layer of titanium dioxide (so thin it is invisible) is being used to coat clothing. This titanium oxide reacts with oxygen, creating a chain reaction that eventually results in the removal of dirt particles without washing. As the girls pointed out ‘great for busy people who don’t have time to clean!’

Anthony, Yuan Min and Ian researched the use of nano-sized particles of zinc oxide in sunscreen. Zinc oxide has been used as sunblock for many years, though, it has never become popular as it forms thick white patches on the skin. Scientists have discovered that if zinc oxide is particles are arranged in a single nano-sized layer, it is does not scatter visible light and becomes transparent, preventing the formation of an unsightly white layer .

Mrs Kitchener

Parents take a Science lesson!!

On April 19 prospective Yr 7 parents visited SJI International to see how we teach. They were involved in several lessons from all subjects and the photos below show them engaed in a science lesson. Some made comment that it was the first time they had been in a science lab for more than 30 years! As you can see they seemed to really enjoy being back.

The scanning electron microscope

The scanning electron microscope (SEM) is capable of creating images of the surfaces of objects at very high magnification. It's amazing the detail that can be seen using this piece of equipment.

Have a look at these images and try to guess what they are of (the answers are at the bottom of this post)

1. (image width approx. 1mm)

2. (image width approx. 0.010mm)

3. (width of bottom image 0.025mm)

4. (image width 1mm)

5. (image width 0.015mm)



Answers:

1. A seed of the tabacco plant

2. Pollen grains from many types of flowers

3. E = red blood cells L=white blood cell

4. The gills of a fish

5. Cholera bacteria

SWEET, VIOLET SACS

Grade 11 Biology HL class has started a practical on an investigation for a more in depth understanding of the process – osmosis.
Osmosis is the movement of water molecules from a region of higher concentration to a region of lower concentration across a partially permeable membrane, so that eventually two solutions will have uniform water potential.

Osmosis is generally about:

A hypotonic solution has a higher water potential than a hypertonic solution.

In our experiment
The objective of our experiment was to prove that osmosis occurs as water molecules move from a hypotonic solution to a hypertonic solution.

Procedures
Step 1: Prepare a cylindrical gas jar with water. Add a few drops of iodine solution so that water turns a visible yellow.
Step 2: Tie one end of the Visking tubing tightly with thread. We need to ensure that there will not be leaks.
Step 3: Using a dropper, insert 3% starch solution to 3/4 of Visking tubing.
Step 4: Insert delivery tube into Visking tubing. We can’t have air bubbles getting into the delivery tube as this will affect the starch solution level in the delivery tube.
Step 5: Tie the other end of the Visking tubing tightly with thread.
Step 6: Using a dropper, add 3% starch solution into delivery tube to ensure that the starch solution level is clear the visible.
Step 7: Rinse the Visking tubing with water lightly to get rid of starch solution that could have accidentally gotten on the external surface of Visking tubing.

Step 8: Using a retort stand, suspend the delivery tube with attached Visking tubing into the gas jar as shown below.

This, however, is a failed experiment because the starch solution is leaking at a very fast rate as seen by the violet trails in the iodine solution. Presence of starch stains iodine violet.

This is how the set-up should look like:

Results

Explanation:
The 3% starch solution in the visking tubing turned dark blue because of the iodine molecules which diffused from the solution in the glass jar into the visking tubing. The iodine molecules moved from a region of higher concentration (outside the visking tubing) to a region of lower concentration (in the visking tubing), thus showing it moved by diffusion.

We also observed that the level of starch solution in the glass tube rose slightly due to the movement of water molecules from the iodine solution into the 3% starch solution by osmosis. This is because water moved from a region of higher concentration of water molecules though the partially permeable membrane (the visking tubing) to a region of lower concentration of water molecules.

The starch molecules did not move out of the visking tubing because starch molecules are too big and cannot diffuse across the visking tubing. Thus, only the contents of the visking tubing turned dark blue because the iodine reacted with the starch.

By Gabriel Woon, Hilda Foo and Joey Lim

View from the bottom

The Physics department is to be found on the ground floor of the new Science block at SJI-International. Mr. Bowen and Mr. Saranam teach Physics to grades 9-11 and Science to grades 7 & 8. Take a look at some of the things that have being going on on the ground floor in the last week…..

Year 10
Year 10 have been trying to figure out electrical circuits and will gladly explain the difference between an emf and a p.d. if you ask nicely. Here they are investigating the relationship between potential difference and current.

Lorraine: Knit one pearl one…

Bryan :Emf or voltage?
Shaun: What’s the (potential)difference?

Year 8
Year 8 have been studying variation and selective breeding. Here they are investigating variation in tomatoes.

Kenny : The investigation is afoot gentlemen!

Thomas: 151,152,153…
Celestine :You missed one!
Thomas : Where? One hundred and forty…..oh no not again!

Year 7
Year 7 have been looking at separating mixtures by filtration and chromatography:

Lots more investigating to do in the coming weeks …wonder what we will discover?

Measuring the size of cells

The FIB 10 JGo class under Ms. Carter experimented with plant cells and animal cells. For plant cells, we used onion cells and human cheek cells for animal cells.

The microscopes in the science lab have the magnification power of x10 for the eye piece and between x4, x10 and x40 for the objective lens. The total magnification can be low power (x40), medium power (x100), or high power (x400). We photographed the cells using our mobile phones.

We first experimented with onion cells (top image). We took a very thin layer of the inner surface of an onion, then we put it on a slide, added a drop of water, and lowered down the cover slip. We looked at the cells under low power and medium power.

With the cheek cells (bottom image), we made use of methylene blue stain instead of water because cheek cells are transparent, so we used methylene blue to make it more obvious. First, we put a drop of methylene blue on the center of the slide. Then we wiped the lining of our cheek with a plastic coffee stirrer and then smeared it on the drop of methylene blue. We looked at the cells with medium and high power, because the cells are much smaller compared to the onion cells.

In order to measure the cell length, we have to know the diameter of field of view of the microscope. So, we measured a ruler under a microscope. The diameter of field of view in: low power=4.2mm, medium power=1.6mm, high power=0.6mm.

In the onion cells picture, the magnification is medium, and there are 9 cells in the diameter of the field of view. Therefore the actual size of an onion cell is 0.47mm.

In the cheek cells picture, the magnification is high, but it’s not clear how many cells there are in the diameter of the field of view. So, we printed the photo and measured the length of a cell in the photo. The diameter of the field of view in the photo is 12.1cm and the length of a cell is 1.35cm. Hence, the actual size of a cheek cell is 0.07mm .

Petrus Bosa Layarda

The Chemistry Club

The first meeting was held on 23rd January 08 with a group of students ranging from Grade 7 to Grade 11, who assembled together in Lab 7 under the supervision and guidance of Mrs. Kitchener.

The activity started with a short demonstration of Charles' Law, which states that the volume of a given amount of dry ideal gas is directly proportional to the Celsius Temperature, provided the amount of gas and the pressure remain fixed. We heated an aluminium can containing a small amount of water to a high temperature to create a region of low pressure inside the tin. When steam is seen escaping from the can, we then quickly placed the can into a basement of cold water, and then it is observed that the can was crushed.

Next, we decided to light up hydrogen filled balloons in a row to create a chain of explosions. hydrogen is a bi-product of the reaction between magnesium and hydrochloric acid. Effervescence was observed when we put a piece of Magnesium ribbon into a glass test tube containing hydrochloric acid. The hydrogen gas produced was collected into balloons. The balloons were lined up using thread and tape, and then lighted (see picture). Hydrogen is highly flammable, when the gas in the balloons caught fire, it exploded.

Overall it was a very successful first meeting.

Christopher Sien and Sarvatrajit Singh

(Answer to last post question: Nitrogen is the atom shown).

A new year and new laboratories

Welcome to the SJI International Science Department blog! It is our intention to regularly post updates about the latest activities in the department to keep you informed about the fantastic classes and opportunities that SJI International science students are involved in. With regular contributions from our students we hope this blog will become an important communication tool for those interested in science in the SJI International community.

The year has begun with much enthusiasm and excitement. We have moved into brand new laboratories which are fully equipped with some excellent technological equipment and already classes are abuzz with students engaging in meaningful learning experiences. Dr Hjorth's and Miss Carter's Gr10 FIB classes have been conducting experiments to look at the effectiveness of washing detergents. Miss Kitchener's Gr11 Chemistry classes have begun studying atomic structure, making full use of the various interactive educational tools on the Internet. In physics Mr Bowen's Gr11 class has been examining magnitude and measurement by looking at things from the smallest particles in an atom to the size of the universe. Mr Saranam's Gr 8 class has been making their own salt crystals, while in Mr Bennett's Gr8 class they have begun to build scale models of the solar system.

Miss Kitchener is also running a Chemistry Club for students as part of the school's co-curricular programme and already many students have signed up. We hope to have them make regular contributions to this blog.

Overall it has been a great start to the year and it is fantastic to see our students so active and happy in not only their science classes but across the whole school.

Before we sign off, can you work out the name of the atom that appears at the top of today's post? Answer in the next post!

Jensen Hjorth - Head of Science, on behalf of the SJI International Science Department.