Does the Mass Add Up：做大众加起来.doc

Does the Mass Add Up?Science LabKendra MacGillivraySNC 1D5/13/2012Mr. StrideLab Report Does the Mass Add Up?Purpose To explore and explain the Law of Conservation of Mass.Hypothesis The mass of the products of a chemical reaction will be the same as the total mass of the reactants.Materials Eye protection and apron Two 125 mL glass beakers 10 mL Pipette Balance or weigh scale Sodium hydroxide (NaOH(aq) Iron (II) sulfate (FeSO4(aq)10 ml Pipette PipettedIron (II) sulfateSodium HydroxideEye ProtectionScience AprondWeigh ScaleTwo 125 ml Glass BeakersFigure 1: Equipment for LaboratoryMethods Using the balance, determine the mass of Beaker 1. Record the mass on Table 1 Add 20 mL of NaOH(aq) (Reactant 1) to Beaker 1 Using the balance, determine the mass of Beaker 1 and Reactant 1. Record the mass on Table 1 Calculate the mass of Reactant 1 and record the mass on Table 1 Using the balance, determine the mass of Beaker 2. Record the mass on Table 1 Add 20 mL of FeSO4(aq) (Reactant 2) to Beaker 2 Using the balance, determine the mass of Beaker 2 and Reactant 2. Record the mass on Table 1 Calculate the mass of Reactant 2 and record the mass on Table 1 Determine the Total Mass of the reactants (Reactant 1 + Reactant 2) and record the mass on Table 1 Carefully, pour Reactant 2 into Beaker 1 Record any observations (e.g., formation of a solid precipitate, colour change) Using the balance, determine the mass of Beaker 1 and the Products of the chemical reaction. Record the mass on Table 1 Determine the change in mass (Mass of Products Total Mass of Reactants). Record the change in mass on Table 1.ResultsTable 1. Mass ChangesPredicted change in mass (decrease, no change or increase)No changeYour reason for your predictionMass should always stay the sameMass of Beaker 1 in grams67.8Mass of Beaker 1 + Reactant 1 (NaOH) in grams88.7Mass of Reactant 1 (NaOH) in grams20.9Mass of Beaker 2 in grams69Mass of Beaker 2 + Reactant 2 (FeSO4) in grams75.2Mass of Reactant 2 (FeSO4) in grams6.9Total Mass of Reactants27.8Mass of Products + Beaker in grams95.7Mass of Products in grams27.9Change in mass (Products Reactants) in grams0.1Observed change in mass (decrease, no change or increase)Almost no changeObserved class results (decrease, no change or increase)Almost no changeFigure 2: Graph comparing total mass of reactants to total mass of products of the chemical reactionWhen the two liquid reactants, sodium hydroxide, a clear liquid, and iron (II) sulfate, a yellowish rust coloured liquid, were combined they produced a grey green solid precipitate.The results of the experiment show that the total mass of the reactants, sodium hydroxide and iron (II) sulfate are approximately the same as the total mass of the products of the chemical reaction produced by combining the two reactants. The total mass of the two reactants was 27.8 grams and the total mass of the products of the chemical reaction was 27.9 grams. The total change in mass was 0.1 grams.DiscussionMass is the amount of matter that makes up any given object and is not determined by the pull of gravity. All objects have a mass that does not vary. In this experiment two chemicals (sodium hydroxide and iron (II) sulfate) were used. The mass of each chemical was determined and combined to predict the total mass of the two reactants. The reactants were then combined and a chemical reaction occurred, creating a solid precipitate. The mass of the precipitate was then measured. The difference between the product of the two reactants on their own and the solid precipitate was +0.1. However, the Law of Conservation of Mass states “the mass of an isolated system (closed to all matter and energy) will remain constant over time” (/wiki/Conservation_of_mass). Put another way the Law of Conservation states that “mass is neither created nor destroyed, and the total mass of substances involved in a physical or chemical change remains unchanged.” (/distils/lab/chemistry/Matter/matter1.html)Therefore, in this or any experiment concerning physical or chemical change the sum of the masses of the reactants will be equal to the sum of the mass of the product, mass will neither be created nor destroyed.In this experiment there did appear to be a very slight change in the mass of the product compared to the mass of the reactants. There are some simple explanations to the why the total mass of the two reactants and the total mass of the products of the chemical reaction when combining the two reactants was not the exactly. They include such human errors as a loss of some of one or both of the reactant when combining them, the possibility of another substance being combined with the precipitate, or the possibility of recording the wrong number as a result of not waiting until the scale had finished measuring accurately.ConclusionIn conclusion, it is possible to