Term 2 Blog Post 3: Lessons and Practicals

Introduction :

In this blog post, I will be talking about the issues and things we learnt in class and a pratical done this term.

What we learnt this term:

So the bulk of what we learnt this term was on Measurements. This was split up into 3 different topics; Instruments, Physical Quantities and Units. So now I will summarise briefly on what I had learnt and reflect on some of the issues.

Use of measuring instruments:

I must say, during this chapter, I got a huge shock. We were introduced to many new apparatus that are common in a laboratory, such as the Bunsen burner, hand lens and microscope. Now that wasn't the part that gave me a surprise. It was when we proceeded to the different measuring instruments, such as measuring cylinders, metre rule and measuring tape, vernier calipers, electronic balance, spring balance, stop watch and thermometers. Now that was quite a lot to me. When I was in primary school, I never knew that, that were so many different instruments used to measure specific units! Well, I did not even think there was a need to measure certain things to such a precise amount. I would always think to myself, if someone wanted to measure something smaller than 1mm, what would he do? I mean, looking at my ruler and seeing how smaller 0.1cm already is, how would someone be able to measure something to the precision of 0.1mm? So there were many of my such questions that were answered, and of course the answer to my previous question was the use of vernier calipers. I don't think I would have ever thought of such an idea.

I would say I had a hard time trying to remember all the different instruments and their different functions or units they measure. Aside from that this chapter was pretty much just like that.

Physical quantities and units:

This part of the chapter was actually quite easy for me, as I had already gone to the National Metrology Centre of Singapore. So basically for this chapter, we were introduced to much bigger and smaller numbers than we ever had since primary school. We also had to know the SI units for measurements such as length, mass, time and temperature. On top of that, we had to determine the appropriate units for physical quantities such as area, volume and density. Oh, and density is also something new to us.

There was also something that we had to remember, and that was the use of prefixes in relation to the units of length and mass. Examples are: milli-, nano-, kilo-.

Mass, Weight and Density:

The only thing new to me here is Density. As we all already know, mass is the amount of matter inside something or someone, while weight is actually the amount of gravitational pull on something or someone. So what exactly is density then? The density of something is defined as mass per unit volume. Which means if we wanted to calculate the density of something, we take its mass, divided by its volume. Also, if the density of something is lower than another thing, then it will float and vice versa. For example, if the density of a steel block is 8, then you put it in a tub of water, it will sink. This is beacuse the density of water is around 1, and since the density of the steel block is higher than 1, it sinks.

During the home learning science lesson this term, we also had some very good and interactive websites where we could understand what density is better. There was also one particular website where we could put different objects into a tub of water and see if it would float or sink, and also virtually change the density of water to see the effects on the things in it.

Practical 12: Forming Compounds

In my opinion, this has to be the most interesting practical done thus far in the entire year. At first, when we were told to get our apparatus and all we had was a strip of magnesium ribbon, I thought it would just be another usual practical experiment. However, when we were told to use the Bunsen burner and after I took a look at the worksheet given to us, I knew that this would be interesting. As I used a pair of tongs to place the magnesium ribbon over the flame, a sudden short burst of white light appeared, and I can tell you, my heart skipped a beat. Never would I have thought that this small strip of ribbon could actually be lit up into such a bright light.

So what has just happened was that a new substance was formed, as the ashes of the magnesium has turned from silvery grey to white, and heat was also involved in the reaction. So basically the word equation for what just took place would be: Magnesium + Oxygen = Magnesium Oxide.

So that was the reacting of two elements. After which we also proceeded to do two more experiments on the reaction of an element with a compound and the reacting of two compounds.

Reacting an element with a compound:

What we did for this experiment was to place half a spatula of iron filings in a test-tube and add dilute sulphuric acid to it. What started to happen was that, effervescence of a colourless and odourless gas could be seen. The test tube soon started to feel warm, which was a clear indicator that heat was released during the entire reaction. So the word equation would be : Iron + Sulphuric Acid = Iron Sulphate + Hydrogen Gas.

Reacting two compounds:

So after that short experiment that I briefly explained in the previous paragraph, we had one last one to complete. It was rather simple, all we had to do was to add some sodium chloride solution with lead(II) nitrate solution all into a test-tube. Then what I saw was that white precipitate after some time and it gradually became more and more. So the word equation for this entire reaction would be Lead(II) nitrate + Sodium Chloride = Lead(II) Chloride + Sodium Nitrate.

Aside from all the experiments that we did, in the pratical worksheet, there was still a section at the last page concerning metals. The first question was asking 3 differences between metals and non-metals. However, the more interesting part was the second section, where we have a 4-paragraph explanation on the uses of some pure metals. Some examples are Aluminium, Copper, Mercuy and Lead. I would say that this worksheet would be very useful to me as there will be parts in the term test that consist of the uses of some pure metals. At the bottom of the page, we were asked to suggest a comercial use for Titanium metal, if Titanium has a high mechanical strength, low density and is very resistant to corrosion. I gave an answer which is pipes, and I certainly was wrong. After some research, I found out that titanium is used for some aircrafts and missiles as its lightweight strength and ability to withstand extremes of temperature.

Conclusion:

I guess that's about all in this pratical and a summary of some of the issues and lessons we had in class. I am sure that all this information will help me in my coming tests and also at the same time increase my knowledge and understanding in Science. I also had lots of fun doing the praticals! So maybe I can call this, "Killing 3 birds with 1 stone!"