Wednesday, October 23, 2019
Reactivity of Metals with Water and Acid Essay
Introduction This report discusses an experiment to study the relationship of the physical and chemical properties of elements in groups and periods to the atomic structure of the elements. The objective of the experiment is to observe what happens when seven metals (magnesium, calcium, iron, lead, copper, aluminum, and zinc) are placed in water and/or hydrochloric acid. The hypothesis is that not all metals will react with the water and/or hydrochloric acid. This report presents the experimentÃ¢â¬â¢s procedures, results, analysis and questions. Purpose To observe relationships between the reactivity of elements and their location on the periodic table. Materials Part A: Reactivity of Metals in Water 1. 2. chemical safety goggles 3. 250 mL beaker 4. test tube (18 mm x 150 mm) 5. test-tube rack 6. scoopula 7. spark lighter 8. Bunsen burner clamped to a retort stand 9. test-tube clamp 10. pH paper 11. paper towel 12. small samples of 1. calcium, Ca(s) 2. magnesium, Mg(s) 3. copper, Cu(s) 1. wooden splint Part B: Reactivity of Metals in Hydrochloric Acid 1. 2. chemical safety goggles 3. 20 mL graduated cylinder 4. 4 test tubes (18 mm x 150 mm) 5. test-tube rack 6. scoopula 7. small samples of 1. magnesium, Mg(s) 2. iron, Fe(s) 3. zinc, Zn(s) 4. aluminum, AI(s) 1. dilute hydrochloric acid (0.5 mol/L) 2. spark lighter 3. Bunsen burner clamped to a retort stand 4. paper towel 5. wooden splint 6. masking tape or test-tube stopper Procedure Part A: Reactivity of Metals in Water The materials were selected and brought to the station. Safety protocol was followed and safety glasses were worn throughout the experiment. The appropriate data tables were drawn in which to record the data observations. The beaker was filled with approximately 250 mL of tap water. The water was tested with pH paper and the results were recorded. On a folded piece of paper towel, the professor placed a small piece of calcium (Ca). Observations of physical properties were recorded. A test tube filled with tap water was placed, mouth down, into the beaker (figure 1) and the calcium was placed in the beaker(amendment: the original procedure asked to select a metal that produced a gas to collect the gas after first attempting the procedure. To avoid wasting time, the gas [if there was] was collected on the first and only attempt). The reaction was observed and recorded. After the reaction was complete, the water was tested with pH paper. This procedure was repeated using samples of magnesium and copper. All results were recorded. The test tube was extracted from the beaker and without flipping it, was placed mouth down in the test tube rack. Using a spark lighter, the Bunsen burner was lit and a wooden splint was lit from the flame. The burner was turned off. Using a test tube clamp, the test tube was lifted and with itÃ¢â¬â¢s opening at the bottom; the burning splint was inserted into the mouth. Observations were recorded. The splint was extinguished with water from the tap and all waste was disposed of. Part B: Reactivity of Metals in Hydrochloric Acid The materials were selected and brought to the station. Safety protocol was followed and safety glasses were worn throughout the experiment. The appropriate data tables were drawn in which to record the data observations. A graduated cylinder was filled with approximately 20.0 mL of dilute hydrochloric acid. 5.0 mL were poured into four clean test tubes, which were then placed on the test tube rack. On a folded piece of paper towel, the professor placed small quantities of magnesium, iron, zinc, and aluminum. The physical properties of each of the metals were recorded. One at a time, each of the metals was carefully dropped into a different test tube of hydrochloric acid. Reactions were observed for a 20 minute period (amendment: because of the lack of time, reactions were only observed for five minutes) and observations were recorded. Masking tape was used to lightly cover the test tube in order to collect gas from the elements that bubbled in the acid. After the reactions were complete, a wooden splint was lit using a Bunsen burner and the masking tape was removed. The glowing splint was held just inside the mouth of the test tube. Observations were recorded and the waste was disposed of. Observations Part A: Reactivity of Metals in Water Element Calcium Magnesium Copper Physical properties Solid, silver, metallic, soft Long, thin, solid, smooth, malleable, silver, shiny Thin, solid, malleable, bronze in colour, shiny Reaction Upon putting the calcium in water, it bubbled and released gas. The water in the test tube was displaced when it was held above the calcium while it was reacting pH before reaction: 7 pH after reaction: 8/9 There was no reaction when the magnesium was placed in the water, therefore no gas. There was no reaction when the copper was placed in the water, therefore no gas. Part B: Reactivity of Metals in Hydrochloric Acid Element Zinc Iron Aluminum Magnesium Physical properties Solid, shiny, silver in colour Rusty, small individual solid flakes, dull Powder, grey/silver Long, thin, solid, smooth, malleable, silver, shiny Reaction Slow reaction, but it eventually started to bubble. Very slow reaction. Few bubbles were produced. Though there was no observed reaction from the aluminum and the hydrochloric acid, further research shows that it does react. It releases heat and the water evaporates. Upon putting the magnesium in the hydrochloric acid, it quickly started to bubble and fizz. Throughout the observation, it also releasedlots of heat. Analysis The objective of the experiment was to observe what happens when seven metals are placed in water and/or hydrochloric acid. Calcium, magnesium, and copper were all placed in water and of the three, only the calcium reacted. Zinc, iron, aluminum, and magnesium were placed in the hydrochloric acid. There was a reaction in every test tube, but the magnesium showed the greatest reaction with iron being the least reactive to the acid. Even though the metals may be in the same period, how it reacts to the water or hydrochloric acid depends on the type of metal. Error(s) When the lit splint was held just above the mouth of the test tube with the magnesium, there was no reaction, unlike the high-pitched popping sounds emitted by other groupsÃ¢â¬â¢ experiments. Perhaps this is because the masking tape was removed from the mouth of the test tube minutes before the wooden splint was lit, giving the collected gas enough time to diffuse. A reason for the zinc and aluminum not reacting with the hydrochloric acid could have involved dirty glassware or the lack of time allowed for observation. Conclusion The purpose of this lab was to explore the patterns in reactivity in the periodic table. Through careful observation and planning during this experiment, the hypothesiswas deemed successful. Not all metals react with water and hydrochloric acid. Questions 1. Rank the elements tested in Part A from least reactive to most reactive. 1. From the elements tested in Part A, calcium reacted the most with water (it produced hydrogen), while both copper and magnesium did not have a reaction. 1. Sort the elements that you tested into groups. State the apparent order of reactivity as one proceeds down a group. Does reactivity increase or decrease? 1. Group 2 (alkaline earth metal): magnesium, calcium Group 8: iron Group 11 (coinage metal?): copper Group 12: zinc Group 13: aluminum For the metals, the reactivity increases as one proceeds down the group. This is because it is easier for electrons to be given farther down the periodic table. 1. Sort the elements that you tested into periods. State the apparent order of reactivity as one proceeds across a period. Does reactivity increase or decrease? 1. Period 3: magnesium, aluminum Period 4: calcium, iron, copper, zinc For the metals, the reactivity decreased as one moves from left to right across periods, because it is easier for electrons to be taken away farther to the left of the periodic table. 1. Is the solution that is produced when a metal reacts with water acidic or basic? 1. The solution that is produced when a metal reacts with water is basic, because the pH increased. 1. Based on your gas test observation in Step 16, what gas is produced? 1. Based on the gas test observation in Step 16, hydrogen gas is produced. This can be determined by the Ã¢â¬Ësqueaky popÃ¢â¬â¢ sound that is heard when the lit wooden splint is placed at the mouth of the test tube. 1. Rank the elements tested in Part B from least reactive to most reactive. 1. In part B, copper would be the least reactive, because there was little-to-no reaction with it and the hydrochloric acid. Iron is the second least reactive, as its reaction was slow but there were a few observed bubbles. Zinc would be the second most reactive and magnesium the most reactive, with a quick reaction and the plenty of heat that was released. 1. Does the reactivity increase or decrease as one moves across a period of elements? 1. As one moves across the periodic table from left to right, for the metals, the reactivity decreases, this is because the farther to the left, the easier it is for electrons to be given or taken away. But for the non-metals, the reactivity increases(excluding the nobles gases), because the farther right, the higher the electronegativity, resulting in a greater exchange of electron. 1. Based on your gas test results, what is the gas produced in these reactions (Steps 16 and 25)? 1. Based on the gas test results and the similar Ã¢â¬Ësqueaky popÃ¢â¬â¢ sound the elements emitted, the gas produced from the magnesium and hydrochloric acid reaction and also the calcium and water reaction is hydrogen gas. 1. Does the reactivity increase or decrease as one moves down a group of elements? 1. As one moves down a group of elements on the periodic table, for the metals, the reactivity increases, this is because the farther down, the easier it is for electrons to be given or taken away. But for the non-metals the reactivity decreases as one goes down because the farther up, the higher the electronegativity, resulting in a greater exchange of electron. 1. Evaluate this investigation. Did the design enable you to collect enough evidence to answer the questions? How could it have been improved? Would your suggested improvements raise any safety concerns? 1. The design was decent, but it did provide all the evidence needed to answer all the questions; a few of the questions required further research. I think the investigation could have been improved by writing clearer instructions and being more descriptive to avoid confusion. Also, students should be able to experiment with different metals to help them expand their understanding of the reactivity of metals in water and hydrochloric acid (this may raise a few safety concerns). 1. Predict what might happen if you were to drop a piece of potassium (or lithium) into a beaker of water. 1. Because potassium is an alkaline metal (lithium as well), it is extremely reactive. I predict that dropping it in water would cause it to react quickly and intensely, and produce hydrogen gas. 1. Connect the trends observed in Parts A and B to atomic radius, ionization energy, and electron affinity. Write a paragraph to explain the trends. 1. The elements moving from left to right across a period, the atomic radius decreases, as does the ionization energy(the nucleus of the atom gains protons).The atomic radius increases moving down a group, but the ionization energy decreases moving down a group (gains protons and new energy shells of electrons).And opposite to the ionization energy, electron affinities increase from left to right across a period. Electron affinities change little moving down a group, becoming slightly more positive.