Term 2 chapters and term 2 test

In term 2, we started to learn about density of irregular objects, Brownian motion, elements, compounds and mixtures and forming compounds. These many topics spurred my interest with their weird names.

----Density of an irregular object----

In density of an irregular object, we had to find the density of objects such as glass stoppers. We were to lower them into measuring cylinders and measure their densities. I felt that this practical lesson was very fun because it actually helped us to learn about calculations. Although the math behind it was easy, however it was still interesting how you had to subtract the volumes to get the volume of the irregular object. I was unable to really do the experiment properly with Samuel Leong because when we dropped the stopper in, we accidentally displaced some of the water in the measuring cylinder, hence the calculation error.We did not lower the glass stopper gently into the measuring cylinder, but had dropped in without even holding on to the string connected to the glass stopper.

However, the practical was still a fun and enjoyable one. We still learnt much about densities of irregular objects. Even though we fooled around with the apparatus, yet we still managed to grasp what the teacher was trying to teach us, which was to find the density of the objects that was irregular.We were fascinated by the densities
of such irregular objects and we learnt a lot about it. The math behind finding density was easy and yet it fascinated me. I had not realized how such simple math could be used to find densities of weird objects. You simply had to find the volume of water before and after the glass stopper is put into it, and subtract the latter from the first and you will get the density of the glass stopper.


----Brownian motion----

During our practical on Brownian motion, we were to observe the Brownian motion of smoke particles in the air. We had to fill a smoke cell with smoke from a smouldering paper and cover it with a glass slip and then illuminate the smoke particles and examine the results. We found out how there were bright spots of light and they were zigzagging in random directions and we found out that they were actually smoke particles and reflect light from the source. We also realized how the bright spots are moving because the air particles bombard unevenly on all sides of the smoke particles causing random and continuous movement.
To find out which are larger particles and which are smaller particles, we can simply look at their speed because larger particles will move slower than smaller particles because they have a larger inertia.

In our practical, we were presented with a new and fascinating question about how we could observe Brownian motion in liquid. I could not figure out anyway to do it, but in the end here is the answer. suspend talcum powder in water and observe the movement under a light source and a powerful microscope.

Interesting facts about Brownian motion: Brownian motion was named after the Scottish botanist Robert Brown who first observed it in 1827. He was using a microscope to look at pollen grains in water, when he noticed that the pollen grains kept moving about. At first he thought that the pollen was alive so he boiled it and tried again but they still moved. Brownian motion provides good evidence that gas consists of invisible molecules moving around randomly at high speeds.

It was very interesting to see the particles zigzag about in high speed. In the above picture, we can see what I really mean when I say that the particles zigzag about in random directions.

----Elements, compounds and mixtures----

In our practical about investigating mixtures and compounds we had to investigate the properties of a mixture and a compound. We made use of a tripod stand, evaporating dish, glass rod as well as wire gauze and Bunsen burner. We also made use of iron filings, sulfur powder, filter paper and a piece of paper magnet.
We used the magnet to try to attract the sulfur powder. nothing happened and the sulfur remained yellow. Then we used the magnet and tried to attract the iron filings, resulting in the filings getting attracted to the magnet. Then we mixed the iron filings and the sulfur powder together and mixed them with a glass rod. We see that it is a mixture of iron filings and sulfur powder. The iron filings are separated from the sulfur powder. Thus we can see how mixtures are not chemically combined and can be separated without chemical means, which in this case is represented by the magnet.

Then we needed to prove compounds and their properties. We heated the evaporating dish we used to show mixtures over a Bunsen burner and observed the compound formed. It was a dark grey solid. When we moved the magnet over to the compound, there was no observable changes and nothing was attracted to the magnet. Thus we can prove how a compound is made through chemical means and cannot be separated using physical methods such as using the magnet.The experiment was not an easy one, because of the powder and the iron filings. they were small and were in such great numbers that they were spilling all over the floor in the laboratory. Also, we made quite a mess when we were trying to make the compound because we were heating the mixture and they sprayed everywhere. Also when the sulfur was heated it gave off such a stench that we had headaches and we could not see what we were doing. We could only hold on to our noses and try not to puke. The sulfur smelt like rotten eggs and rotten fish! However it was a fun practical because it involved a lot of the Bunsen burner as well as mixing stirring the iron filings and the sulfur powder together.
After the practical, We learnt that mixture retains the properties of its constituents, but compounds do not retain the properties of its constituents. I also learnt how heat or light energy is needed for a compound to form, but for mixtures heat and light energy is not required.When surfing the internet, I came across several questions that required thinking processes. These questions may not be ones that are asked in tests, but they are still interesting.

An unknown, clear liquid is given to you in a beaker. You transfer the liquid from the beaker to a clean, empty test-tube, and begin to heat it. After a while, you see vapors (which on further analysis you discover are vapors of water) rising from the test-tube, and pretty soon, all that's left are a few crystals of salt stuck to the edges! Was that liquid an element, compound or a mixture?

mixture. The constituents of a mixture can easily be separated by physical processes, which in this case, was the application of heat. The salt had been dissolved in the water to form a true solution of common salt, where the particles of salt were invisible through the naked eye as well as through a microscope, resulting in the solution being absolutely clear.

 

Aqua regia was a liquid used by alchemists to separate silver from gold. Was it an element, compound or mixture?

mixture. Aqua regia was a mixture of concentrated nitric acid (HNO3) and hydrochloric acid (HCl) and was used to dissolve gold, which would leave silver. 

A dish is given to you, which contains a blackish-yellow powder. When you move a magnet over it, you are amazed to see black particles, (which you find out are iron) fly upwards and get stuck to the magnet, and all that's left in the dish is a yellow powder, which you discover to be sulphur (sulfur). Was your original powder an element, compound or mixture?

mixture. The powder was a mixture of sulphur, which is yellow in colour, and iron, which is magnetic and blackish in colour. When the magnet was passed over the mixture, the iron got attracted to it, leaving the sulphur in the dish. Hence in mixtures, the properties of the constituents aren't lost. this question was related to a topic that we went through about elements, compounds and mixtures.

You have just won a block of pure 24-carat gold. Have you just procured an element, compound or mixture?

element. Gold, like oxygen, hydrogen and over 100 other substances is classified as an element. Elements are further grouped into metals, non-metals and metalloids. 22-carat (or "karat") gold, or 22 parts of gold alloyed with 2 parts of silver or copper, is usually preferred to 24-carat (pure) gold in jewellery.

 

*Water* is what all life in the world depends on. Is it an element, compound or mixture?

compound. A molecule of water is made up of two atoms of hydrogen and one atom of oxygen, which means that it is made up of more than one kind of atom, and hence isn't an element. Also, since it can only be broken down into hydrogen and oxygen (its constituent elements) by chemical processes (such as electrolysis), it is a compound.

Although these questions were easy and comprehensible, they contained the basics of elements compounds and mixtures and were thus worthy of reading. In the above I have mentioned questions on elements, compounds and mixtures. these questions provide basic understanding on the properties of compounds, mixtures and elements.

----Forming Compounds----

 In this practical, we were to investigate the formation of compounds by reacting two elements, reacting an element with a compound and reacting two compounds. We made use of magnesium ribbon, iron filings, dilute sulfuric acid, lead(II) nitrate solution and sodium chloride.

PART A

We had to burn the magnesium ribbon over a Bunsen burner and when it catches fire we were to hold it over an evaporating dish to collect the ashes formed and record our observations. We realized how the magnesium ribbon burned with a bright white light. The ashes are a powdery white substance.( Ash is white in color.) Then, a new substance is formed because the physical appearance has changed from silvery grey to white in color and heat is also involved in this reaction.In the compound, oxygen combined with magnesium to get the new compound. Or it can be stated with this:

 magnesium + oxygen--------> magnesium oxide.

 

 

PART B Reacting an element with a compound
In this part of the experiment we were to place half a spatula of iron filings in a test tube and dilute sulfuric acid to the depth off about 2 cm. Then we saw that iron filings are dissolving into the sulfuric acid and bubbles are forming. A new substance has formed because the test tube felt warm so there was heat energy involved. From this I can learn how sulfuric acid reacts with iron filings.

PART C reacting two compounds

We placed sodium chloride solution in a test tube. WE used a dropper and added lead (II) nitrate slowly to the test tube.WE saw white precipitate in the colorless solution.
lead(II) nitrate + sodium chloride = lead(II) chloride + sodium nitrate. After the excercies we were told to stats three differences between metals and non metals

Metals are good electrical and thermal conductors but non metals are not. Metals are ductile but non metals are not ductile.
UESES OF SOME PURE METALS
summary of this passage is:

  Aluminumis a light metal that can be easily rolled out into very thin yet strong sheets. It is resistant to corrosion, which makes it suitable for milk bottle caps. It does not melt easily and can withstand high temperatures, which is why it is used to make containers for prepacked foods and for making foil for covering the food it cooks. Many drink cans are also made of aluminum.

Copper is good at conducting electricity and is ductile. It can be pulled into thin wire. So copper is used for making electrical wires. Gold, silver and platinum are used for making jewellery and they are unreactive metals that stay shiny. They can be used to make the coating parts in electrical switches.

Mercury is an unusual metal that is liquid at room temperature. It is used in thermometers.

Lead is a heavy metal which is extremely malleable and it is used for waterproof edging to roofs such as chimneys. before it was known to be poisonous it was used for making water pipes and toy soldiers. Lead is also used for shielding radiation.

Titanium can be used to make ships, glass covers or laptops because it is a durable material.

----WHICH CAN DISSOLVE MORE----

The practical was to find out if the solubility of different solutes differ in the same solvent. We had to keep the volume, mass and temperature of the solvent constant. We measured 20 cm cube of water into a beaker, and added 1 g of common salt using the electronic balance. We added the common salt to the water, then stirred the common salt in the water and continued adding 1 g of salt until no more will dissolve in the stirring. the total mass of the salt added before it would not dissolve is about 5 g. I repeated the steps 1 to 4 using baking soda and iodine crystals, and the results were 1 and 0 respectively, so I learnt that salt is the most soluble in water. adding 0.1 g of salt to the water could help me to find the solubility of the solutes in a solvent more accurately. From the experiment I can conclude that different solutes have different solubility.

----Separating techniques----

This experiment was for me to separate a mixture of salt and sand. i made use of beakers, filter funnels, glass rods, evaporating dishes, tripod stand, wire gauze, Bunsen burner and a retort stand. I also made use of a mixture of salt and sand and filter paper. My task was to separate a mixture of salt and sand. Salt can be dissolved but sand cannot. I had to make use of water and filtration and dryness to separate them. I was supposed to place a mixture of salt and sand in a beaker and add 10cm cube of water into the beaker and add more water to dissolve the salt if necessary.Using filtration, sand is separated from the mixture. Using evaporation to dryness, salt is separated from the mixture.


Chromatography

A question to find out if black ink is really black. The aim of the experiment was to find out the colors in different brands of black ink. This experiment was very practical and I learnt a lot about chromatography from it. I learnt about how you should never place the ethanol and water mixture above the ink dots to prevent a mistake in the results of the experiment. I also learnt how the dots should have a fixed difference from the end of the paper, which in this case is three centimeters.The experiment was very effective and successful and i was able to see the different colors of the black ink which was blue yellow and purple, along with a mix of brown and green. In the discussion section there was a question discussing about chromatography used on chocolate. i felt that it would be useful to learn about it and hoped that one day i would be able to do something like that. The experiment really helps in finding out the colors in the chocolate. The experiment was meant to inform us and teach us about the uses of chromatography and how to use it. I have learnt a lot from the practical about the experiment.


----TERM TEST 2----


the term 2 test was harder than the term test one but it was easier to comprehend than the first test, so I feel. the questions that came out were easy to understand and I also felt that the questions that came out were more and had lesser marks in each of them, so it was easier to get the marks. I felt that the questions were clear and concise. Even though my results were not as good as they were in test 1, yet I still improved while doing the test, and i got 28 and a half over 40. I feel that if I had studied the notes that were presented to me more conscientiously I would have been able to score higher in the test itself. i feel that the graph question was mark leniently and thus I was able to salvage marks to pull up my total score.