Properties of Chemical Reactions
Ms. Whitty, Science 10
Fiona Adams, November 1st, 2012
Chemical reactions are a part of our daily lives, from rusting metal to making bread to leaves changing colour in the fall. A chemical reaction is the process that occurs when two or more substances combine to produce a chemical change. When a chemical reaction takes place, the change is indicated by one or more qualitative properties. The colour or odor could change, gas could be produced, a precipitate – a solid substance in a solution - could be formed, or energy could be absorbed or released. The substances initially involved in a chemical reaction are called reactants. When chemical reactions occur, the end result is called a product. Products usually have different properties than reactants; bonds between atoms will be changed during the reaction, switch the atoms’ arrangement in different compounds. A compound is a chemical substance that consists of two or more different chemically bonded elements. In this experiment, several different compounds are being worked with – potassium iodide, lead (II) nitrate, acetic acid and sodium bicarbonate. The purpose of this experiment is to determine whether or not a reaction has taken place using qualitative and quantitative analysis.
Part 1 -
Qualitative observations of both potassium iodide and lead (II) nitrate were recorded in a table. Then, the equipment and chemicals needed were gathered – potassium iodide and lead (II) nitrate, a graduated cylinder, Erlenmeyer flask, small test tube, rubber stopper, and small scale. Using the graduated cylinder, 10 mL of potassium iodide solution was measured and poured into the Erlenmeyer flask. Next, the lead (II) nitrate solution was poured into the small test tube until it was approximately half full. The test tube was placed inside the Erlenmeyer flask, and sealed with a rubber stopper – the solutions were not mixed. The mass of flask, stopper and contents were determined by being placed and weighed on a small scale. The mass determined was then recorded in another table. The Erlenmeyer flask was tipped so the previously separate solutions were allowed to mix, and the new mixture was again weighed and recorded in the second table. Changes in appearance from the original solutions were recorded in the first table. Lastly, leftover materials were disposed of. Part 2 –
Qualitative observations of both acetic acid and sodium bicarbonate were recorded in a third table. Equipment and chemicals were gathered – acetic acid and sodium bicarbonate, a small scale, two plastic “weigh boats”, scoopula, and graduated cylinder. The first weigh boat was placed on the scale and the scale was “zeroed”. One scoop of sodium bicarbonate was poured into the weigh boat with the scoopula, and the results were recorded in a fourth table. Next, the second weigh boat was placed on the scale and zeroed. Using the graduated cylinder, 15 mL of acetic acid was measured and poured into the weigh boat on the scale. The mass of the acetic acid was recorded in the fourth table. The sodium bicarbonate, measured previously, was poured into the weigh boat of acetic acid, and qualitative observations of that were recorded in the third table. When the reaction was complete, the mass of the products shown on the scale was recorded in the fourth table. Lastly, leftover materials were disposed of.
Qualitative Observations Part 1 –
Before the reaction took place, both the potassium iodide and lead (II) nitrate had similar characteristics – they were both in a liquid state, as well as being clear and colorless. After the reaction, the qualitative observations of the new substance showed several differences. It was yellow in color, and a grainy precipitate had formed. The substance remained in a liquid state. (Table 2) Quantitative Observations from Part 1 -
Mass of Reactants and Apparatus (g)
Mass of Products and...
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