Term+1+Issues+in+Teaching+and+Learning+Science

Last year, I did not have a thorough comprehension of the topic element, mixture and compounds and thus did not score as well as I had expected in the chemistry section. Therefore, I vowed to work hard this term to make up for the things I did not know. The periodic table is a very challenging but at the same time an enriching topic. The different elements are placed in different groups and have many different characteristics. Each group of elements have their own characteristics and have different names, such as alkaline metal, alkaline earth metal and transition metals. As for the last group of elements, they are the noble gases and are very unreactive. It is challenging because we have to memorise the chemical symbols for the common elements.Atomic structure and equation writing are two of my favourite topics. It is somewhat related to the periodic table, because of an element's valence electron. The number of valence electrons in an element determines which group it is in. The drawing of the atoms is my favourite part of the topic atomic structure. As for equation writing, I was confused at first because of the balancing part. I always thought that I had to balance the equation first, but Mrs Chu corrected my mistakes and I realised that the balancing have to be done at the last part. Acids, bases and salts is mostly learnt through experiments. We did different kinds of experiments regarding acids, bases and salts, such as neutralisation and identifying of ammonia. Many wrong concepts that I have were corrected through these experiments. I always thought acids were more corrosive than alkali, and I thought that concentrated acids were always stronger than diluted acids. However, there are many corrosive alkali to and concentrated weak acids are not always stronger than diluted strong acids. I also learned about some basic properties of acids and alkalis, as stated in the title. I learned that universal indicators and natural indicators change colour based on the pH of the solution they are in. I also learned about the effect of acids and alkalis on Methyl Orange and Phenolphthalein. I read that such indicators have a sharp change in their colours and are used in a kind of volumetric analysis known as titration. Universal indicator is not good for titration because its change in colour at the end point of titration is not sharp. One of the 16 Habits of Mind states the need for accuracy and precision. If the change in colour is not sharp, we cannot get an accurate end point. I read that the error for titration is only 0.1ml thus a sharp change is needed. All in all, chemistry is very interesting and I found it actually quite fun and easy to study. I could not understand how I did so badly for it last year but now, I have found the way to studying chemistry and acing it.
 * Learning Points**

One of the lab sessions involved the investigation of the action of dilute acid on metals. We are supposed to carry out the experiments and write down the different observations. From there, we will come out with conclusions.  Procedure:  1. Pour dilute hydrochloric acid into a clean test tube to a depth of 3cm. 2. Drop a piece of magnesium ribbon into the test tube of dilute acid. 3. Quickly close the mouth of the test tube with your thumb for a few minutes. 4. Light a wooden splint and hold it at the mouth of the test tube. Observe what happens. Place a piece of damp red litmus paper and a piece of blue litmus paper over the mouth of test tube. Record your observations in a table. 5. Repeat steps 1 to 4 using: (a) iron fillings (b) zinc powder (c) copper turnings Observations:  Observation when metal is added to acid <span style="color: #000000; font-family: Arial,Helvetica,sans-serif; font-size: 90%;">Reaction between hydrochloric acid and: <span style="color: #000000; font-family: Arial,Helvetica,sans-serif; font-size: 90%;">Magnesium, Iron and Zinc-Effervescence of colourless and odourless gas was observed. <span style="color: #000000; font-family: Arial,Helvetica,sans-serif; font-size: 90%;">Copper-No visible change. <span style="color: #000000; font-family: Arial,Helvetica,sans-serif; font-size: 90%;">Effect of gas on burning (lighted) splint <span style="color: #000000; font-family: Arial,Helvetica,sans-serif; font-size: 90%;">Reaction between hydrochloric acid and: <span style="color: #000000; font-family: Arial,Helvetica,sans-serif; font-size: 90%;">Magnesium, Iron and Zinc-The lighted split was extinguished and a 'pop' sound was heard. <span style="color: #000000; font-family: Arial,Helvetica,sans-serif; font-size: 90%;">Copper- <span style="color: #000000; font-family: Arial,Helvetica,sans-serif; font-size: 90%;">Effect of gas on damp red and blue litmus paper <span style="color: #000000; font-family: Arial,Helvetica,sans-serif; font-size: 90%;">Reaction between hydrochloric acid and: <span style="color: #000000; font-family: Arial,Helvetica,sans-serif; font-size: 90%;">Magnesium, Iron and Zinc-Damp red litmus paper remained red and blue litmus paper remained blue. <span style="color: #000000; font-family: Arial,Helvetica,sans-serif; font-size: 90%;">Copper- <span style="color: #000000; font-family: Arial,Helvetica,sans-serif; font-size: 90%;">Name and chemical formula of gas formed <span style="color: #000000; font-family: Arial,Helvetica,sans-serif; font-size: 90%;">Reaction between hydrochloric acid amd: <span style="color: #000000; font-family: Arial,Helvetica,sans-serif; font-size: 90%;">Magnesium, Iron and Zinc-Hydrogen gas, H2. <span style="color: #000000; font-family: Arial,Helvetica,sans-serif; font-size: 90%;">Copper- <span style="color: #000000; font-family: Arial,Helvetica,sans-serif; font-size: 90%;">Conclusion: <span style="color: #000000; font-family: Arial,Helvetica,sans-serif; font-size: 90%;">1. Dilute metals react with reactive metals to produce hydrogen gas. <span style="color: #000000; font-family: Arial,Helvetica,sans-serif; font-size: 90%;">2. Acid+Metal = Salt +Hydrogen. <span style="color: #000000; font-family: Arial,Helvetica,sans-serif; font-size: 90%;">In conclusion, I found this lab lesson very enriching as it was quite an eye-opener for me, allowing me to discover the source of the formula whereby acid and metal gives you salt and hydrogen. Also, the experiment also enable us make use of lab equipment like litmus paper and lighted splint. When doing this experiment or those similar to this, we have to wear safety goggles to protect the eyes and cannot taste the chemicals as they can be poisonous etc. and can harm us. Teamwork is definitely essential because two people can verify the results, making them more accurate in case there is human error, and experiments can be carried out much faster as one can do the experiments while another can record the results.
 * Practical lessons**

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 90%;">One use of acids is in making fire extinguishers. One kind of fire extinguisher is the water extinguisher – what an irony. It works by using high pressure to blast water at the fire. The water extinguisher has a glass vial that contains sulfuric acid. The extinguisher’s body contains baking soda solution. When the operator pushes the plunger down to break the vial, the two chemicals react, and water and carbon dioxide are produced: <span style="display: block; font-family: Arial,Helvetica,sans-serif; font-size: 90%; text-align: center;">H2SO4 (aq) + 2NaHCO3 (aq) à Na2SO4 (aq) + H2O (l) + CO2 (g) <span style="font-family: Arial,Helvetica,sans-serif; font-size: 90%;">As the gas pressure (carbon dioxide) inside the extinguisher increases, it pushes a jet of water out of the extinguisher’s nozzle.
 * Application of acids and alkallis**

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 90%;">Another use for acids (more specifically sulfuric acid) is in car batteries. Car batteries are a type called a lead-acid storage battery. In a lead-acid battery, the negative electrode is a plate made out of the metal lead. The positive electrode is made of lead (IV) dioxide. The electrolyte is sulfuric acid which ionizes in water: <span style="display: block; font-family: Arial,Helvetica,sans-serif; font-size: 90%; text-align: center;">H2SO4 (aq) à 2H+ (aq) + SO42- (aq) <span style="font-family: Arial,Helvetica,sans-serif; font-size: 90%;">At the negative electrode, the sulfate ions (SO42-) oxidize lead to produce electrons: <span style="display: block; font-family: Arial,Helvetica,sans-serif; font-size: 90%; text-align: center;">Pb (s) + SO42- (aq) à PbSO4 (s) + 2e- <span style="font-family: Arial,Helvetica,sans-serif; font-size: 90%;">At the positive electrode, lead (IV) dioxide reacts with electrons from the negative electrode, together with hydrogen and sulfate ions, and is reduced to lead (II) sulfate and water: <span style="display: block; font-family: Arial,Helvetica,sans-serif; font-size: 90%; text-align: center;">Pb4+ (aq) + 2O2+ (aq) + 4H+ (aq) + SO42- (aq) + 2e- à PbSO4 (s) H2O (l) <span style="font-family: Arial,Helvetica,sans-serif; font-size: 90%;"> By combining these two half equations, we get:

<span style="display: block; font-family: Arial,Helvetica,sans-serif; font-size: 90%; text-align: center;">Pb (s) + 2SO42- (aq) + Pb4+ (aq) 2O2+ (aq) + 4H+ (aq) à 2PbSO4 (s) + 2H2O <span style="display: block; font-family: Arial,Helvetica,sans-serif; font-size: 90%; text-align: left;">This is a redox reaction as there is a transfer of electrons from lead atoms to lead (IV) ions. This is a transfer of electrons produces electricity. <span style="font-family: Arial,Helvetica,sans-serif; font-size: 90%; line-height: 0px; overflow: hidden;">

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 90%;">Perhaps one of the well-known uses of bases would be using calcium hydroxide to test for the presence of carbon dioxide. Below shows the reaction between calcium hydroxide and carbon dioxide: <span style="display: block; font-family: Arial,Helvetica,sans-serif; font-size: 90%; text-align: center;">Ca(OH)2 (aq) + CO2 (g) à CaCO3 (s) + H2O (l) <span style="font-family: Arial,Helvetica,sans-serif; font-size: 90%;">Calcium carbonate (CaCO3) is insoluble in water and precipitates out, which turns the calcium hydroxide “cloudy”.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 90%;"> Ammonia is a base (more specifically an alkali) and has many uses. Ammonia (NH­3) might not appear like an alkali because it does not contain the hydroxide ion. However, when mixed in water, in forms ammonium hydroxide: <span style="display: block; font-family: Arial,Helvetica,sans-serif; font-size: 90%; text-align: center;">NH3 (g) + H2O (l) ↔ NH4OH (aq) <span style="font-family: Arial,Helvetica,sans-serif; font-size: 90%;">The double arrow means that while some ammonia molecules are being converted to ammonium hydroxide, a few of the ammonium hydroxide molecules are being converted back to ammonia molecules. Hence, ammonia is a weak alkali. However, ammonia especially when concentrated is nonetheless corrosive. Ammonia evaporates easily and if concentrated vapors enter one’s lungs, it might burn through his lung cavity. Despite its dangers, ammonia is a well known cleaner.


 * Home-Based Learning**

Home-based learning is a very good practice for me to practice all the things that I have learnt about elements and periodic table. I had much fun completing the crossword puzzle, even though it is only optional. I have always liked crossword puzzles and putting it in studying makes the HBL very interesting.Then, I completed the online worksheet on alkaline metals and halogens. As I had just finish learning about the alkaline metals and halogens, which is the first and seventh group, this online exercise gives me a chance to get practice on my newly learnt knowledge.The online learning is very meaningful as it is almost no different from normal lessons, except for the absence of a teacher and discussions with classmates. Yet, I can learn the same things I learn from normal lessons during the home-based learning. Thus, I am looking forward to the next home-based learning.


 * A comic strip regarding acids and bases**