Cells: An Analogy

This is an analogy of cells using animal cells. You probably may not have heard of some of the organelles.

Body: Earth

System: Continent

Organ: Country

Tissue: State

Cell: City

Cell membrane: City border with guards to monitor people entering and leaving the city

Free Ribosome: Individual shop

Ribosome on Rough Endoplasmic Reticulum (RER): Shop part of a franchise

RER: Franchise Headquarters

Smooth Endoplasmic Reticulum (SER): Recycling Plant

Vesicle pinched from RER: Transport vans for shop products

Vesicle pinched from SER: Transport vans for recycled products

Golgi Apparatus: Factory for processing, refining and modifying imported products

Vesicle fusing with Golgi Apparatus: Transport vans arriving and unloading goods

Vesicle pinching off from Golgi Apparatus: Transport vans with ready-to-go goods

Vesicle fusing with cell membrane: Transport vans unloading goods for export out of city

Cytoplasm: Free land

Nucleus: Government

Chromatins: High post officials

Centriole: Civil servants

Nucleolus: President/Prime Minister

Vacuole: Storage Plant

Mitochondria: Power Plant

If you happen to find that my analogy is incorrect at some parts, please let me know so I can change it. Thanks!

Between Chem and Bio

These are some pics of cells. These diagrams contain the different parts of cells and the less known organelles.

Crystallisation

Here is an interesting video explaining crystallisation. It is a silent video but the images speak for it.

Separating Mixtures

Here are some ways to separate the following mixtures:



1) A mixture of non-magnetic materials and iron



Method: Use a magnet



2)A mixture of water, a solid that can dissolve in water and a solid that cannot (eg. water, salt and sand)



Method: filter the mixture to remove the sand, then use distillation to separate the salt and the water



3) 2 liquids that do not mix (eg. water and oil)



Method: Slightly more complicated. There is a special machine built to do so. It is called the API oil-water separator. You can find out about it in Wikipedia at this site: http://en.wikipedia.org/wiki/API_oil-water_separator



4) Air and petroleum

This is definitely more difficult... There is a special type of machine that is used. It is big, bulky and complicated. You can see it at these sites:

http://www.onyxnet.co.uk/clients/mastrad/bub.htm

http://www.geneq.com/catalog/en/air_release_petro.html

The aftermath of coke and mentos

Hi people, these are some choice pics from the coke and mentos experiment. Also, here is the wrap-up of our group's experiment.

Group members: Sarah Tay, Rachel Seah, Stella (who, by the way, took all the photos, thanks!) and me

Objective: To find out how the number of Mentos affects the height of the fountain.

Hypothesis: The more mentos put in, the higher the fountain will go.

Items used: Several tubes of mentos, three bottles of 1.5 litre coke, two meter rulers, two measuring cylinders, one of which got jammed, and one poncho that made me look like Little Red Riding Hood.

Procedure: We were supposed to drop in 10, 20 and 30 mentos respectively into each bottle of coke, but for the first one, Sarah only managed to unjam 2 mentos, so the rest were stuck when the explosion occurred.

Secondly, Sarah managed to fit 16 mentos into the measuring cylinder and pour it all in at once. Stella expertly captured a shot of the coke in mid-air.

Finally, we put in 10 mentos at once. Of course, being me, I put the stupid ruler crooked so the reading was inaccurate.

Our final conclusion was that we were correct, but up to a certain point the coke would stop dissolving the mentos and we would need to add more coke instead.

Here are explosion pics of other groups.

Separation of mixtures

How to separate mixtures:

1. Hand Separation

Example: Separating salt and sand

2. Filtration

Example: Sand and Water

3. Distillation

Example: Alcohol and Water

4. Chromatography, for separating different substances to determine whether they are banned substances

5. Etc. There are a whole lot of other techniques but they are too complicated and not required at this level.


http://www.chemteam.info/Matter/SeparationOfMixtures.html

The Elements

The periodic table of elements was thought up in 1869 by the Russian Chemist, Dmitri Mendeleev. They are in this order: 1. Hydrogen 2. Helium 3. Lithium 4. Beryllium 5. Boron 6. Carbon 7. Nitrogen 8. Oxygen 9. Fluorine 10. Neon 11. Sodium 12. Magnesium 13. Aluminium 14. Silicon 15. Phosphorus 16. Sulfur 17. Chlorine 18. Argon 19. Potassium 20. Calcium


















Also, for those who enjoyed Miss Liang's elements song in class today, I am posting a video, probably by the same makers of Li Shan's Newton video as both use Lego.

Bibliography



http://www.flickr.com/photos/dullhunk/2053007240/



http://en.wikipedia.org/wiki/Periodic_table_%28large_version%29



http://en.wikipedia.org/wiki/Periodic_table

National Vertical Marathon 2009

This year's national vertical marathon was held on 8 Feb 2009, Sunday, at Republic Plaza. Republic Plaza is 280 metres tall with 66 floors and 1 basement. It has 15 double-decker vertical lifts and is one of the three tallest skyscrapers in Singapore.

Links:

http://en.wikipedia.org/wiki/Republic_Plaza,_Singapore

Tallest buildings

There is a three-building tie for the tallest building in Singapore. They are:

1.OUB Centre 280 m, 63 floors

2.UOB Plaza 1, 280 m, 66 floors

3. Republic Plaza, 280 m, 66 floors


As for the world's tallest buildings, here they are!

1. Burj Dubai, Dubai, The United Arab Emirates
Built in 2009
162 floors, 818 m

2.Taipei 101, Taipei, Taiwan
Built in 2004
101 floors, 508m

3. World Financial Center, Shanghai, China
Built in 2008
101 floors, 492m

Bibliography:

http://en.wikipedia.org/wiki/List_of_tallest_buildings_in_Singapore

http://www.infoplease.com/ipa/A0001338.html

Volcanic eruption 5 times in a row

Alaska's volcano, Mount Redoubt, erupted 5 times over night after being extinct for at least 20 years. It sent ash up into the air at a height of more than 9 miles high into the air. It sent light dustings of ash down, This ash can cause irritation to eyes, injure skin and block breathing passages.

Lab Symbols Video

Hello, this is a funny lab symbols video from Youtube. The wording may be a bit faint though, so you might have to pause and rewind to see some parts clearly. Enjoy!

Between Physics and Chemistry

Most people know about the famous coke and mentos issue. However, do you know why? This Mythbusters video explains in detail. Unfortunately, I could not embed it here due to company policies of Discovery Channel.

http://www.youtube.com/watch?v=kMXPOqovSBs

Basically, this is what happens:

The ingredients required to create the sensational explosion is as follows.

1. CO2 gas found in soft drinks

2. Artificial Sweetener (which is why diet coke is better than normal coke)

3. Gum Arabic

4. Gelatin

5. The process of Nucleation. Mentos surface is full of tiny craters, and during this process the aforementioned ingredients interact with each other, causing the CO2 to escape to the surface. This is evident from the fact that non-mint mentos, with a waxed surface, reacts very slowly or not at all as the wax covers the craters.

This is also linked to Ms. Liang's post on the discussion forum. Ms. Liang posted on the discussion forum about a Pepsi and Necco wafer experiment. According to the video, Necco wafers release the hydrogen component from hydrogen hydroxide, which is a fancy name for water. Hydrogen is highly flammable, thus fire can form on the surface of the glass.

Necco wafers consist of: sugar, corn syrup, gelatin, gum, colorings and flavorings. From the ingredients, you can tell that Necco wafers are more of powdery candy than wafers as there is no flour in it. I think this would be an interesting experiment to try. However, Necco wafers are manufactured in the USA, so it would be hard to obtain them here in Singapore. Thus, to try this experiment, one could just add gum and gelatin to Pepsi as the other ingredients are redundant. These are pics of necco wafers below.

I think I will try this when I have the time an post more about it.

Links:

http://www.necco.com/OurBrands/Default.asp?BrandID=7

http://www.youtube.com/watch?v=kMXPOqovSBs

http://www.maniacworld.com/pepsi-and-necco-wafers.html

Convection currents

Today Mr. Lim talked about convection currents in class. He posed two questions for us: 1. Since warm air rises and and cold air sinks, will a taller person feel colder than a short person? 2. based on the same concept, will people on the 40th floor feel warmer than on the 15th floor? If yes, why do people claim to feel "cooler" on the uppermost floors?

I think that a tall person would probably feel warmer. This is because they are higher up and the warm air will circle around them. Surprisingly, I have also observed this very often: My taller friends would be sweating profusely, while my shorter friends are huddling together trying to get warm!

As for the second question, I don't think it makes a difference since every level has air-conditioning! As for people feeling "cooler" on the top levels, it is because that is where the cooling unit for the entire building is.

Ice, Water, salt and Ice cream

I have mentioned this very briefly in one of my earlier posts, entitled Measurements and Density. This time, I shall post more about it. Firstly, the density of ice is less than that of water. This is obvious as ice cubes float in a glass of water when you put them in. Simple right? But why is this so? Well, the answer is simple: When water freezes to form ice, it traps air in it. Air is less dense than water, so it causes the ice to float.

Secondly, if a glass is filled with water and ice cubes are placed in the glass, when the ice cubes melt will the water level rise? The answer is no, the water level will NOT rise. At first, I also thought that the water level would rise. However, once I read the explanation, it made perfect sense. The reason is that when ice melts, its volume is still the same so it will take up the same amount of space that it took up when it had not melted yet.

Lastly, we were asked to research on the effects of impurities on water. Well, this is what I know: In cold countries, salt, an impurity, is thrown on the roads to melt the snow and ice. This is because impurities lower the melting point of ice. This same concept is applied to make ice cream. You can just pour sugar and milk into a freezer bag and seal it, then place it into a larger bag, already filled with crushed salt. Make sure both bags are tightly sealed, and then shake the bags vigorously(but not so vigorously that they split open or smash!) After some time, the contents should solidify and turn into delicious homemade ice cream!

I found a video on Youtube summarising the above instructions in a 1min 18 sec clip. Enjoy!

http://www.elmhurst.edu/~chm/vchembook/122densityice.html

http://sg.answers.yahoo.com/question/index;_ylt=AqAdCXkAnMkY8xceJjXqoAQh4wt.;_ylv=3?qid=20080208133726AAWySCd

http://www.wikihow.com/Make-Ice-Cream

Challenger disaster

I read about this and decided to post it, not just because it is related to thermal physics, it also shows how ignorant Man is.

On January 28, 1986, the Challenger was supposed to conduct the TISP (Teacher in Space Program). In other words, for the very first time, a teacher would be boarding the Challenger to visit space. However, the temperature was too cold (29 degrees F). The engineers who made the Challenger told the NASA managers that they should wait until the temperature reached 58 degrees F. This is because the low temperatures might cause the O-rings to not seal properly. The O-rings kept hot gases, preventing them from escaping.

However, NASA really wanted to launch the flight, so the managers decided to give the go-ahead anyway. Just as Challenger was pulling away from Earth, one of the O-rings failed to seal, causing the hot gas to escape. Flames shot out from one slide of the rocket and licked at the hydrogen tank. Seconds later, the tank exploded, and all seven crew members, including the teacher, died on the spot.

This shows how important it is to consider the safety facts instead of rushing into things. Due to the cold weather, the O-ring had contracted and became too stiff to seal properly. This caused 7 innocent people to be killed.

This is a video showing the live recording of the Challenger explosion.

Centre of Gravity

I found out several things about the centre of gravity. Firstly, the centre of gravity is at the middle of things, in other words, at the very core of the object. Also, it is what causes things to balance themselves. The first time the concept of the centre of gravity was brought up was when Archimedes used this concept to explain the balance and lack of resulting moment when two objects are balanced in a specific way. Hence, if you have a sphere, its centre of gravit would be at the core. This is also why it is harder for spheres to balance: they have considerably smaller cores and less centre of gravity.

http://en.wikipedia.org/wiki/Center_of_mass

The Upside Down World Map

I've always wondered about the Earth. I mean, the Earth is a sphere, so wouldn't that mean that people at the South Pole and at the bottom half of the Earth are standing upside down? I know that the reason why they don't fall off is gravity, but wouldn't they feel weird standing upside down? I asked my dad, and he said that although theoratically half the Earth's inhabitants are "upside down" at any one time, nobody looks upside down because to them, their half of the Earth is the right way up and the other half is upside down!


Then, he showed me this "upside down worlds map" made in Australia. Australia is known as Down Under because it is, according to the world, near the bottom of the Earth. However, in this map, Australia is challenging this. This world map, as its name suggests, has Antarctica and Australia at the top of the world and South America on top of North America. It shows another way of looking at the Earth. Cool, isn't it?


This picture is kind of small, but you can click on it to view a page where it is much, much, much larger. Enjoy!

The North Pole Issue

Today we talked about gravity and the North Pole. I did a bit more research and found out that although both poles have more gravity than the other parts of the Earth, the North actually has more gravitational pull than the South as Antartica is the Southern continent and it is a very high plateau so it would be higher up and consequently have less gravity than the North, which is in the middle of a deep ocean. This is also the same reason why the South is colder than the North. Hence, Mr. Lim was wrong to say that the North Pole has equal gravity to the South Pole.

This is the site where I did my research. http://sg.answers.yahoo.com/question/index;_ylt=AkNOnOfUtpM8NsVKD_Nlolwh4wt.;_ylv=3?qid=20070726222930AAUa3Hd

Forces at Work

Hi guys, I found this cool video on forces. Enjoy!

Forces

We discussed forces in class today. Mr. Lim gave us a question to chew on: If there is an object of weight 1N on the ground, and a force of 1 N is applied to lift it, will the object be able to be lifted into the air? My theory is that it will not be lifted. This is because there is an equal force acting on both sides of the object, namely, upwards lift and downwards weight. Hence, the object will not move.


Take this picture as an example. The four forces are acting on it with equal strength. Hence, the box does not move. If you look at FN and Fg, they are the two forces we are focusing on. The box is neither moving up nor down, hence the equal forces have no effect on it and the box is not being lifted.

Quicksand

Today Mr. Lim told us to research on quicksand in relation to the formula Pressure=Force divided by Area. According to Wikipedia, Quicksand is a non-Newtonian liquid. That means that the liquid seems solid when untouched but when stepped on it quickly becomes a liquid and then quickly solidifies around you again. This is because the pressure applied causes the person to slowly sink down. However, if a person applies enough force and is quick enough, it is even possible to walk on quicksand or other such liquids.

The same concept is applied with trying to get out of quicksand. You have to slowly and methodically move about towards the edge or something to grab onto. By keeping calm and not panicking, and taking deep breaths, you remain bouyant. Although it is a long and tedious process, you willl eventually be able to get out.

Meniscus 2 (Follow Up)

I have managed to find the definition of surface tension. Surface tension is what causes the surface portion of liquid to be attracted to another surface. Based on this, I infer that polar molecues attraction is caused by surface tension. That's one question answered.

As for the other question... I suppose it would be very hard to even test it, as non-polar materials are likely to be opaque, and hence the result cannot be observed. However, if the theories are correct, liquids should not form a meniscus of any sort when they are placed in a container made of a non-polar material.

Meniscus

I researched on meniscus and found many answers, mostly too scientifc ones. However, I finally managed to come across a clear but simple explanation. There are two websites which I got my answer from.

Basically, water has polar molecues, just like glass. Polar molecuse tend to stick togther, so the water sticks to the edge of the measuring cylinder. Hence, the water will tend to form a curve and creep up the edge of the cylinder. This will result in the formation of a concave meniscus, as depicted in A. A convex meniscus, depicted in B, is very rare but may be formed by liquids like mercury where the molecules of the liquid have a stronger attraction to each other than to the container.

What I'm wondering is, if a cylinder of a different material is used, will it also form a meniscus and why? Surely not all material have polar molecues? And what does surface tension have to do with this?

These are the websites that I used for my research.

http://en.wikipedia.org/wiki/Meniscus

http://answers.yahoo.com/question/index?qid=20080917134724AArrlg8

Measurements and density

Today, Mr. Lim wrapped up the topic on Measurements and Units. He also went through the class assignment on IVLE with us. At the end, he gave us two questions to think about. The first was: There is a beaker of liquid with a density of A grams/cubic cm. A represents any natural number. There is also a solid that cannot be dissolved at the exact same density. Where in the beaker of liquid will it be? At the surface, in the liquid or at the bottom of the beaker?

In my opinion, this question is no practical as no two substances are identical. Each substance is unique and hence no two substances have the same density. Even ice and water, different states of the same substance, have different densitieas ice is less dense than water. Hence, this is not likely to happen.

However, in the event that it does happen by a stroke of luck... If it were a liquid, both liquids would mix together and form a mixture. However, since it is a solid, perhaps it would be in the liquid itself as that is the closest it gets to mxing. Also, to float would mean it is less dense and to sink would mean it is denser, so it would probably be in between.

The second question is as follows: Water always has a meniscus at the suface where it curves instead of being fully straight. Why? Even Mr. Lim is not too sure but he says it has something to do with surface tension. I think it is because air is pressing against the surface of water, causing it to bend and curve slightly. I shall research more on this subject when I have time.

Scenario Presentation 2

We had the rest of the scenario presentations. There were 3 groups left. The first group had this scenario: In a production line, 10000 small screws are to be sorted into packs of 50 each. Manual counting would be too tedious. Suggest ways in which the sorting may be done.

This problem seems quite tricky. However, if you think hard about it, the solution is actually pretty simple.


The group had two solutions. 1. Use an electromagnet. Adjust the resistance of the electromagnet such that it attracts 50 screws each time. However, Mr. Lim said that this solution was not very relevant as the electromagnet would be likely to attract either all the screws or none at all. Hence, this solution was not likely to work.


2. Use a weighing scale. Count the first 50 screws and weigh them. Subsequently, grab a handful of screws and weigh them. Compare the reading to the first reading of 50 screw and adjust the number of screws accordingly. This solution is both practical and feasible. It is based on how shopkeepers weigh biscuits or ham using the weighing scale and add more or take out some based on the weight of the products.


The next group had a relatively more common scenario, but explaining it was more difficult. This was their problem: A spring balance will give a different reading on the Moon than from that on Earth. A beam balance, however, will give the same reading. Explain why.


The group's answer is as follows: A spring balance measures weight, which is dependant on gravity. The Moon has less gravity than the Earth, hence the reading differs. However, a beam balance measures mass, which is constant no matter what. Short and sweet, but very clear.


The final group had a very interesting topic. How do submarines float and sink at will?


In my opinion, this group had the most detailed presentation. They explained how air is pumped into the ballast tanks to force water out so that the submarine would float. On top of that, they included a lot of other information such as diagrams, and information on the Kursk Russian submarine disaster. They talked about how a faulty Dummy torpedo had allowed flammable liquid to leak through and explode the front of the submarine, letting water in and causing the submarine to sink.

At the end of the presentation, they gave us question to think about: If a submarine sinks to the seabed, why is it no longer available to move off? The answer is that there is no water under the submarine to create a lift force, hence the submarine is stuck there until rescue workers drop a rope down to haul it back up. I enjoyed this group's presentation the most.

I enjoy thought-provoking lessons and topics like the ones Mr. Lim gave us. I hope we'll be able to have more of such lessons in the future.

Scenario Presentation Part 1

We had to present our work to the class. Li Shan's group went first. They were supposed to measure the approximate amount of water in Mac Ritchie Reservoir based on the map and the fact that the reservoir was 5 m deep.

They certainly thought through their scenario very well. The group gave two possible solutions. The first was to use the scale to calcuate the length and width of the reservoir, then multiply it by the depth for the final answer. The second was to draw the shape of a cylinder on the map. The cylider covered most of the reservoir. After that, they used a formula to calculate the volume of the cylinder and used the scale to convert it to live size. I found the presentation clear, concise, well-thought and interesting.

It was our turn next. I think we did okay. At least no one seemed confused when we explained our method.

We were supposed to finish off all the group presentations, but we were running late again.

Physics Scenario Slides

Scenario solving

Okay, this post is rather late but I didn't have much time to set up the blog earlier on. Anyway, Mr. Lim gave us these scenarios to solve. We were supposed to come up with solutions to our assigned scenario in groups. I was in the same group as Jasley and Abigail. Our scenario was as follows:

You are given a length of copper wire with a small diameter. The only measuring instrument available to you is the meter ruler. Explain how you would measure the diameter of the wire with an acceptable degree of accuracy.

At first, we were stumped as it seemed impossible. Then, Mr. Lim told us we could have a pencil to use as part of the materials. After that, everything just snapped into place. We came up with a simple but effective solution:

To find out the diameter of the copper wire, first we have to twirl the wire round the pencil. Then, measure the length of the pencil. Then, find out how many twirls it takes to make the circumference of the pencil and divide it for the diameter of the copper wire.

Pretty neat, isn't it?