Pregnancy and Delivery

Today, Dr Tan showed us a video on Pregnancy and Delivery. The video was about a woman going through her pregnancy. The video shows us different stages of the baby in the mother's womb. It also tells us that when the baby is about to be delivered, the head will be facing downwards towards the womb. However, there are some cases where the baby's head is not facing down. This is dangerous during delivery as the baby might die of suffocation in the mother's cervix. Also, the arms of the baby might also dislocate when delivering the baby. In most cases, the doctor will advise the mother to opt for cesarean section instead for the safety of the baby. After watching the video, i now know the hardship our mothers went through in giving birth to us. Dr Tan also shared his experience when his wife went through labour.

Reproduction in Man

In this topic, we learn about the changes we go through during puberty and about our sex organs. In male, the sex organ is called the penis, while in females, the sex organ is called vagina. In males, the testis produce the male hormones and male gametes which are also sperms. These sperms contain the genes of the male. In females, the ovary produces the female hormones and female gametes which are also called eggs or ova. These ova contain the female genes.

We also learn about the menstrual cycle. This cycle is when the uterus lining breaks down and disintegrate forming blood. Also, by looking at the timeline of the menstrual cycle, we know when the female is fertile and when she is not.

Colours of light

The first time i heard of this was when i was in kindergarten.All i knew about it was that there were 7 colours in the rainbow. But after learning about this, i now know that the colours on the rainbow are not place by random. It is placed by how much they refract. Also, i learnt that if shine a certain colour onto a coloured surface, different colours will give u different results. But it is not like if u shine red it will give u red that kind. It is of a different pattern.

Optics

In this topic, we learnt about lenses. we learnt about the different lenses and what are their uses. We also learnt about reflection and refraction. These two are completely two different things. For reflection, it means the light rays reflecting on a surface. The angle of incident and angle of reflection will be the same. For refraction it means the light rays passing from a less dense medium to a denser medium. The angle of incident will not be the same as the angle of refraction. Critical angle is something that we learnt. It is when the angle of refraction is 90 degrees. Thus the angle of incident will be the critical angle. We also learn about total internal reflection. It is when the incident ray is in the less denser medium. When the angle of incident is bigger than the critical angle, total internal reflection occurs.

Acids Bases and Salts.

In this topic, we learnt about the PH level of different acids and alkaline. For acids, the PH level will be below 7, while for alkaline, the PH level will be above 7. If the PH level is 7, it means neutralism has happened and the substance is water. Alkaline are also called bases. When a acid react with bases, it produces a salt and water. The acids we use in our laboratory are diluted acids but that does not mean that they are not corrosive. It may still be dangerous if these acids come in contact with us. In a strong acid, almost all the molecules are ionized in water. For weak acids, it is the opposite. Almost all the molecules are not ionized with only a few ionized.

After learning this topic, i relised that acids can be used in many ways and not only in labs. The experiments in the science lab were also fun when we used to litmus paper to check for the PH level of the acid or base.

Periodic Table

We learnt about this in secondary 1 but it was not as detailed as in sec2. In this topic, we learnt about how this table was created, the atomic mass and number. We also learnt that the elements are classified by their characteristics. For example, in group 1, all the elements are alkaline. Alkaline elements are shiny. For the second group is the halogens. They are combine with metal to produce salts. The third one is The Noble Gases.

After this topic, i learnt more about elements.

reflection after term test 3

Before this test, i was very nervous as i was not good in physics as compared to biology. Thus i started revision refraction and other physics stuff very early. In the end, it turned out that my physics did better than my biology ): After this, i now know that revising for only 1 topic for a test that is going to test 2 topics will not be effective even though u are confident in the other. Even though i got a1 for this test, i feel that i was really lucky and i should revised more on biology also.

Ecology

When i first heard that we are going to do this subject, i thought it would be similar to the kind that we learnt in primary school which is about the food chain and about which animals are prey and which animals are predator. But after learning it, i realised there were more than what i learnt in the past. At first, i did not understand what was going on as i was not good in this. But after lots of revision and practise, i finally understood the whole thing. As i didnt do well in ecology in the class test, i will try to improve on it so as to be ready by EOYs

Reflection on the term 2 science test

Before this test, i studied very hard as i wanted to get an A1. I spent most of my time on science than i ever did before. As i was not good in chemical equations, i studied and practiced everyday. Soon after, I become very good at it and could balance the equation well. I also studied very hard for physics as i was not so good in reflection and drawing light rays. In the end, my effort paid off. I GOT AN A1 !! I was very delighted as i did not do that well in the first term test. This told me that the way to achieve something u want is to believe in yourself and practice practice and practice :D

Ace on sulfuric acid.

Q: More Sulfuric acid, H₂SO₄, is made in the United States than any other chemical. Research on the production and uses of sulfuric acid and write a report on your findings.

What is sulfuric acid? Sulfuric acid is a extremely dangerous and oily acid. It has a melting point of -2 C and a boiling point of 327 C. When you are mixing acid to water stir it slowly, much heat is generated with Sulfuric acid. It is one of the cheaper acids in the world. Pure and concentrated sulfuric acid is does not occur naturally due to its affinity to water. It is also a part of acid rain that is formed due to atmospheric oxidation of sulfur dioxide in presence of H2O.

Sulfuric acid is the product of the U.S. chemical industry produced in largest quantity in terms of mass. About 40 million tons are produced annually. Sulfuric acid can be used in many places like removing rust. The following are some common uses.

Manufacture of Sulfuric acid:

There are two major processes (lead chamber and contact) for production of sulphuric acid, and it is available commercially in a number of grades and concentrations. The lead chamber process, the older of the two processes, is used to produce much of the acid used to make fertilizers; it produces a relatively dilute acid (62%–78% H2SO4). The contact process produces a purer, more concentrated acid but requires purer raw materials and the use of expensive catalysts. Some sulphuric acid is also made from ferrous sulphate waste solutions from pickling iron and steel and from waste acid sludge from oil refineries.

Lead Chamber Process

In the lead chamber process hot sulphur dioxide gas enters the bottom of a reactor called a Glover tower where it is washed with nitrous vitriol (sulphuric acid with nitric oxide, NO, and nitrogen dioxide, NO2, dissolved in it) and mixed with nitric oxide and nitrogen dioxide gases; some of the sulphur dioxide is oxidized to sulphur trioxide and dissolved in the acid wash to form tower acid or Glover acid (about 78% H2SO4). From the Glover tower a mixture of gases (including sulphur dioxide and trioxide, nitrogen oxides, nitrogen, oxygen, and steam) is transferred to a lead-lined chamber where it is reacted with more water. The chamber may be a large, boxlike room or an enclosure in the form of a truncated cone. Sulphuric acid is formed by a complex series of reactions It condenses on the walls and collects on the floor of the chamber. There may be from three to twelve chambers in a series. The acid produced in the chambers, often called chamber acid or fertilizer acid, contains 62% to 68% sulfuric acid. After the gases have passed through the chambers they are passed into a reactor called the Gay-Lussac tower where they are washed with cooled concentrated acid (from the Glover tower); the nitrogen oxides and unreacted sulphur dioxide dissolve in the acid to form the nitrous vitriol used in the Glover tower. Remaining waste gases are usually discharged into the atmosphere.

Sulfuric acid is prepared industrially by the reaction of water with sulfur trioxide, which in turn is made by chemical combination of sulfur dioxide and oxygen either by the contact process or the chamber process. The lead chamber process is used to produce much of the acid used to make fertilizers. It produces a relatively dilute acid (62% - 78%). The contact process produces a more concentrated acid but requires purer raw materials and the use of expensive catalysts. Some sulfuric acid is also made from ferrous sulfate waste solutions from pickling iron and steel and from waste acid sludge from oil refineries.

Use of Sulfuric Acid

The uses of sulfuric acid are so varied that the volume of its production provides an approximate index of general industrial activity. Its main use is in phosphate fertilizer production, both superphosphate of lime and ammonium sulfate. It is widely also used to manufacture chemicals, e.g., in making hydrochloric acid, nitric acid, sulfate salts, synthetic detergents, dyes and pigments, explosives, drugs, other acids, parchment paper, glue and wood preservatives. It is used in the purification of petroleum to wash impurities out of gasoline and other refinery products. Sulfuric acid is used in processing metals, e.g., in pickling (cleaning) of metal, electroplating baths, nonferrous metallurgy. Rayon is made with sulfuric acid. In one of its most familiar applications, it serves as the electrolyte in the lead-acid storage battery commonly used in motor vehicles (acid for this use, containing about 33% H2SO4 and with specific gravity about 1.25, is often called battery acid).

Use of Sulfuric Acid

Sulphuric acid is one of the most important industrial chemicals. More of it is made each year than is made of any other manufactured chemical; more than 40 million tons of it were produced in the United States in 1990. It has widely varied uses and plays some part in the production of nearly all manufactured goods. The major use of sulphuric acid is in the production of fertilizers, e.g., superphosphate of lime and ammonium sulphate. It is widely used in the manufacture of chemicals, e.g., in making hydrochloric acid, nitric acid, sulphate salts, synthetic detergents, dyes and pigments, explosives, and drugs. It is used in petroleum refining to wash impurities out of gasoline and other refinery products. sulphuric acid is used in processing metals, e.g., in pickling (cleaning) iron and steel before plating them with tin or zinc. Rayon is made with sulphuric acid. It serves as the electrolyte in the lead-acid storage battery commonly used in motor vehicles.

Ammonium sulphate

It is formed by reacting synthetic ammonia and sulfuric acid. It is an important nitrogen fertilizer. It is commonly used as an artificial fertilizer for alkaline soil. It is also used as agricultural spray adjuvant for water soluble insecticides, herbicides, and fungicides. As a flame retardant, it lowers the combustion of a material.

Removing rust

As it is very corrosive and cheap, it is commonly used with Hydrochloric acid in removing rust. However, since it is highly corrosive, it tend to corrode the metal together with the rust. Therefore, other acids like ethanoic acid are used as they are not so corrosive.

Hazards

Concentrated Sulfuric acid is very corrosive to everything, including skin. It can cause bad burns if you get it on yourself. Even tiny microdroplets that you can barely feel start itching until you get it rinsed off with water. It is very reactive with many chemicals. It is used to digest organic stuff down to elemental states, only the elemental ions are left. It reacts violently with water unless lots of water is used. It gets very hot very fast. When it becomes hot, it gives off a harmful gas that is corrosive to breathe or let it touch the skin.

http://ibchem.com/IB/ibnotes/full/ope_htm/sulphuric%20acid.htm

http://chemicalland21.com/industrialchem/inorganic/sulfuric%20acid.htm

Science for fun

I attended the science for fun course with Josiah and Pei Yu. At first i thought that it would be something like a lecture and we had to take notes or something like that. But after I entered the course, i realised it was doing experiments and other interesting stuff. The first experiment that we did was the Hand Boiler. When we squeeze the bulb containing a liquid, the liquid rises to the top of the bulb. Another experiment i like is the Oobleck. It is an example of a non-Newtonian fluid. It can act like a liquid when held loosely in your hand but it can also act like a solid if you apply force on it. When I slowly put my hand into the Oobleck, my hand sinks into it like a liquid. However when we apply force on it, it becomes as hard as a solid. I felt very fascinated with it as I have never encountered anything like that before.

Quicksand is also a non-Newtonian fluid. When undisturbed, it appears to be solid ("gel" form), but when it is disturbed like when a person attempts to walk on it, there is a sudden decrease in its viscosity (a measure of the internal resistance of a fluid). Then the water and sand in the quicksand separate and dense regions of sand sediment form; it is because of the formation of these high volume fraction regions that the viscosity of the quicksand seems to increase suddenly. Someone stepping on it will start to sink. To move within the quicksand, a person or object must apply sufficient pressure on the compacted sand to re-introduce enough water to liquefy it. The forces required to do this are quite large: to remove a foot from quicksand at a speed of 0.01 m/s would require the same amount of force as "that needed to lift a medium-sized car.”

Because of the higher density of the quicksand, it would be impossible for a human or animal to completely sink in the quicksand, though natural hazards present around the quicksand would lead people to believe that quicksand is dangerous. In actuality the quicksand is harmless on its own, but because it greatly impedes human locomotion, the trapped person is normally harmed by other factors like solar radiation or dehydration.

Reflection on the term 1 science test

I felt that i made many careless mistakes during the test. Instead of spending time on the main section, i spent quite a lot of time thinking of how to do the bonus question. As a result, i made lots of careless mistakes in section B. E.g is instead of writing Na for the symbol of sodium, i wrote 's'. I should have studied harder and memorised the symbols by heart.