Laboratory Lessons

I find laboratory lessons fun and enriching. We were given a chance to conduct experiments on the topics we had learnt. Like this, it would be much easy to understand it as we would be able to see with our own eyes. I definitely enjoyed the laboratory lessons as we would be able to experience it ourselves without just reading it from a book. At first, I was not able to understand the topic on acid and bases, however, after conducting experiments like 2P06 When Acid Meets Alkali, I am able to see more clearly. When an Acid mixes with an Alkali, salt and water would be formed. We conducted an experiment with dilute hydrochloric acid and dilute sodium hydroxide solution and after the mixture was evaporated to dryness, we observed that a white solid was formed and it was salty in taste. Hence we can conclude that an acid reacts with an alkali to produce a salt. Hydrochloric acid + sodium hydroxide -> sodium chloride + water. I hope that there would be more laboratory lessons in the future.

2011 Term 3 Reflections

I think that this term was quite easy. We learnt about lenses, colours of light and ecology. To me, lenses was quite difficult. We had to remember all the types of images that can be formed with a convex lens, know the properties of it and the uses. It was because we needed to draw the ray diagram. However, after much practice, I am able to understand more. I think that ecology was quite easy. We need to know food chains, adaptations and carbon cycle. It was quite easy to understand and remember. Colours of light was also quite easy. Once I was able to understand the concept and remembering the combinations of the colours, I had no problem doing it. For example, I know that when a red object is placed in yellow light, the object would appear as red because yellow is made up of red and green. Like this, I can use this concept to do on other situations. When a red object is placed in magenta light, it would appear red also as magenta contains red as it is made up of blue and red. I scored quite well for my term test partly because chemistry was not tested. =P I would need to improve on my lenses and revise more on drawing the ray diagrams.

Global Warming

Global Warming

Global warming is the continuing rise in the average temperature of Earth's atmosphere and oceans.The instrumental temperature record shows that the average global surface temperature increased by 0.74 °C (1.33 °F) during the 20th century. They indicate that during the 21st century the global surface temperature is likely to rise a further 1.5 to 1.9 °C (2.7 to 3.4 °F) for their lowest emissions scenario and 3.4 to 6.1 °C (6.1 to 11 °F) for their highest.

Causes

The main cause of Global Warming is the orbital eccentricities of Earth and variations in the Sun’s output. Global Warming occurs in cycles caused mainly by changes in the sun’s energy output, and the sun’s relative position to the earth.

Global warming is also caused by increased concentrations of greenhouse gases in the atmosphere, resulting from human activities such as deforestation and burning of fossil fuels. Industrialization, deforestation, and pollution have greatly increased atmospheric concentrations of water vapor, carbon dioxide, methane, and nitrous oxide, all greenhouse gases that help trap heat near Earth's surface.

Over 95% of the greenhouse effect is the result of water vapor in Earth's atmosphere. But because water droplets held in suspension (clouds) make almost as good a reflector as they do a thermal insulator, there is little rise in daytime temperatures due to the greenhouse effect. Any greenhouse warming, if it does occur, is limited to primarily increasing nighttime temperatures.

Interesting fact: The world's natural wetlands produce more greenhouse gas contributions annually than all human sources combined.

Consequences

An increase in global temperature will cause sea levels to rise. Sea level could rise between 7 and 23 inches (18 to 59 centimeters) by century's end, the IPCC's February 2007 report projects. Rises of just 4 inches (10 centimeters) could flood many South Seas islands and swamp large parts of Southeast Asia. Some hundred million people live within 3 feet (1 meter) of mean sea level, and much of the world's population is concentrated in vulnerable coastal cities. In the U.S., Louisiana and Florida are especially at risk.

Glaciers around the world could melt, causing sea levels to rise while creating water shortages in regions dependent on runoff for fresh water. An increase in global temperature will also change the amount and pattern of precipitation, a probable expansion of subtropical deserts. The growth of deserts may also cause food shortages in many places. A follow-up report by the IPCC released in April 2007 warned that global warming could lead to large-scale food and water shortages and have catastrophic effects on wildlife. More than a million species face extinction from disappearing habitat, changing ecosystems, and acidifying oceans.

Warming is expected to be strongest in the Arctic and would be associated with continuing retreat of glaciers, permafrost and sea ice. Other likely effects of the warming include more frequent occurrence of extreme weather events including heatwaves, droughts and heavy rainfall events, strong hurricanes, species extinctions due to shifting temperature regimes, and changes in agricultural yields.

Reflections:

I feel that global warming has created many problems like the increase in temperature leading to the rise in sea level due to the melting of the glaciers, change the amount and pattern of precipitation and causing more natural disasters like droughts, flood and hurricanes. Thus, we should play a part to stop global warming by controlling our emissions of greenhouse gases. Greenhouse gases traps heat near the Earth’s surface, causing the rise in temperature. We should cut down on our industrialization, deforestation, and pollution as they would greatly increase concentrations of greenhouse gases like carbon dioxide and water vapour. We should start caring for the Earth as early as now as the consequences would be deadly and it would badly affect our future generations and by then, it would be too late to regret and try to make changes as the damages would already be done and it would be very hard to be undone.

Speed of Light

Speed of Light

The speed of light in vacuum is believed to be both universal in nature and constant in time. Its value is 299,792,458 metres per second and it is approximately 186,282 miles per second. It is the maximum speed at which all energy, matter and information in the universe can travel.

History of Speed of Light

In 1667, Galileo Galilei is often credited with being the first scientist to try to determine the speed of light.

His method: Galileo and his assistant each took a shuttered lantern, and they stood on hilltops one mile apart. Galileo flashed his lantern, and the assistant was supposed to open the shutter to his own lantern as soon as he saw Galileo's light. Galileo would then time how long it took before he saw the light from the other hilltop. However, his experiments took place over terrestrial distances and the timing methods available to him were far to crude to make a successful determination given such distances and the very great speed of light hence he was unable to measure the speed of light.

In 1676, Olaus Roemer, a Danish astronomer, first successfully measured the speed of light. Roemer's estimate for the speed of light was 220,000,000 metres per second.

His method: It was based on the observations of the eclipses of the moons of Jupiter. Roemer noticed, while observing Jupiter's moons, that the times of the eclipses of the moons of Jupiter seemed to depend on the relative positions of Jupiter and Earth. If Earth was close to Jupiter, the orbits of her moons appeared to speed up. If Earth was far from Jupiter, they seemed to slow down. Reasoning that the moons orbital velocities should not be affected by their separation, he deduced that the apparent difference must be due to the extra time for light to travel when Earth was more distant from Jupiter. Using the commonly accepted value for the diameter of the Earth's orbit, he came to the conclusion that light must have traveled at 220,000,000 metres per second.

In 1729, James Bradley used the aberration of light method to estimate the speed of light and he measured it to be 301,000,000 metres per second.

In 1849, Hippolyte Fizeau used the toothed wheel method to estimate the speed of light and he measured it to be 315,000,000 metres per second.

In 1862, Leon Foucault used the rotating mirror method to estimate the speed of light and he measured it to be 298,000,000 metres per second.

In 1907, Rosa and Dorsey used the electromagnetic constants method to estimate the speed of light and they measured it to be 299,710,000 metres per second.

In 1926, Albert Michelson used the rotating mirror method to estimated the speed of light and he measured it to be 299,796,000 metres per second.

In 1950, Essen and Gordon-Smith used the cavity resonator method to estimate the speed of light and they measured it to be 299,792,000 metres per second.

In 1958, K.D. Froome used the radio interferometry method to estimate the speed of light and he measured it to be 299,792,500 metres per second.

In 1972, Evenson et al. used the laser interferometry method to estimate the speed of light and he measured it to be 299,792,456.2 metres per second. The development of lasers with very high spectral stability and accurate caesium clocks made even better measurements possible.

In 1983, to further reduce uncertainty, the seventeenth CGPM replaced the definition of the metre with its current definition, thus fixing the length of the metre in terms of the second and the speed of light. This definition fixed the speed of light in a vacuum at precisely 299,792,458 metres per second.

Reflections:

I feel that all these people who tried to measure the speed of light is very creative as they were able to think of methods to measure it. I was also touched by their determination to try and measure the exact value of the speed of light. Many scientist in the past believed that light has a infinite speed and there is no way to measure it. However, it was Galileo who was willing to put in effort and try to measure the speed of light and even though he failed, it was a motivation for other scientists to try and measure the speed of light. The measurement of the speed of light has helped in many areas of physics and it is very important. This taught me that we should not give up but try to think of different methods to figure it out when sometimes it might seem to be impossible.