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What is the effect of reactant particle size on the rate of a chemical reaction? By: An Nguyen

Research Facts In order for a chemical reaction to occur, the particles, atoms or ions, which are REACTANTS, must physically come into contact with one another. Anything that increases the frequency of these encounters will increase the rate at which PRODUCTS are formed. The rate of a chemical reaction can be increased by increasing the temperature of these reactants. If any of the products or reactants involved in a chemical reaction are gases, the rate of reaction will decrease as pressure on the system is increased. As more surface area are expose the rate chemical reaction increases When water reacts with Alka-Seltzer, one of the products of the reaction is carbon dioxide gas. When two substances react together, they can form new chemicals or products. In this chemical reaction, the vinegar and baking soda react and create carbon dioxide. It is these bubbles of gas that inflate the balloon. 01 Bayer HealthCare. "Alka-Seltzer Plus - Student Science Experiments." Alka-Seltzer -- Alka Seltzer Plus. Bayer, 2011. Web. 01 Dec. 2011. <http://www.alka-seltzer.com/asp/student_experiments_1.html> Wilbraham, Antony C., and Dennis D. Staley. Pearson Chemistry. Boston, MA: Pearson, 2012. Print. HowStuffWorks, Inc. "HowStuffWorks "Why Does Alka Seltzer Fizz?"" HowStuffWorks "Science" 2011. Web. 01 Dec. 2011. <http://science.howstuffworks.com/innovation/science-questions/question116.htm>.

Introduction and Background A chemical reaction is a process, in which one or more substances (reactants) are chemically changed into one or more new substances (products,) this also causes a change in the composition in the valence electrons. In this experiment, Alka-Seltzer will be used to demonstrate the chemical reaction in which the rate of CO2 production will be measured. The main ingredients of Alka-Seltzer tablets are aspirin, citric acid, and sodium bicarbonate (NaHCO3). When sodium bicarbonate dissolves in water, it dissociates (splits apart) into sodium (Na+) and bicarbonate (HCO3−) ions. The bicarbonate reacts with hydrogen ions (H+) from the citric acid to form carbon dioxide and water. The reaction is described by the following chemical equation: The purpose of this experiment is to determine if changes reactant particle size will effects on the rate of a chemical reaction. The experimenter predicts that as the reactant particles are smaller, the chemical reaction rate will be faster. 01

01 Experimental Design Diagram Title: What is the effect of reactant particle size on the rate of a chemical reaction? Hypothesis: If the reactant size particles are smaller, then it will react faster. Independent Variable: Different Reactant Size Particles Particle Size Whole Tablet Tablet Broken in Half Tablet Broken in Quarters Powdered Tablets Trials 3 Dependent Variable: Rate of Chemical Reaction (sec) Controlled Variables (constants): Same amount of water (mL) Same amount of temperature Same type of reactant Same type of water 01

Materials and Equipment At least 12 Alka-Seltzer® tablets Sheet of blank paper Hammer Piece of scrap wood Thermometer (-10°C to 110°C) Clear 12 ounce (355 mL) drinking glass (or larger) Note: Use Pyrex glass when working with water heated on the stove or in the microwave Measuring cup Masking tape Stirring rod Tap water Stop watch Lab notebook Pencil Knife A helper ***Safety Considerations: None are needed, because the reactant use in this experiment is very stable. Safety Equipment Goggle Gloves Apron

Procedures

How Does Reactant Particle Size Affect the Rate of Chemical Reaction? DV: Rate of Chemical Reaction (sec) IV: Trial 1 Trial 2 Trial 3 Mean/Ave Whole Tablet 55.2 49.1 48 50.8 Tablet Broken into Half 48.5 47.6 48.2 48.1 Tablet Broken into Quarters 41.4 42.3 42.6 42.1 Clear(control) 31.3 32.4 30.9 31.5 01 *The recorded data was the total reaction rate of different reactant particle when react with H2O molecules. The rates were measured in seconds.

Data Analysis 01

As the reactant (Alka-Seltzer) are broken into smaller particles (powdered tablet) the rate of reaction increases, the rate of chemical reaction for smaller particle (powdered tablet) are faster or quicker than the rate of bigger particles (whole tablet); when the small particle react with water it the rate seem to increase the most, its final rate of reaction that were recorded are the smaller particles (powdered tablet) have a faster rate of chemical reaction than other bigger particles ( a whole tablet, a tablet broken in half, and a tablet broken in quarters.) After twelve trials, the average, or mean, of chemical reaction (seconds) was calculated to observe the changes that happen. When whole tablets of Alka-Seltzer, were but into water, it mean or average of the chemical reaction rate is 50.8 +/- seconds; when tablets of Alka-Seltzer are broken in half, were but into the water, it mean or average of the chemical reaction rate is 48.1 +/- seconds; when tablets of Alka-Seltzer are broken into quarters, were but into water, the mean or average of the chemical reaction rate is 42.1 +/- seconds; and when tablets of Alka-Seltzer are broken into quarters, were but into water, the mean or average of the chemical reaction rate is 31.5 +/- seconds. The independent variable is the different reactant size particles; the dependent variable is the rate of chemical reactions measured in seconds. Powdered particle of Alka-Seltzer has the fastest rate of chemical reaction, next are the broken into quarter tablet of Alka-Seltzer, then the broken in half tablet of Alka-Seltzer and last the whole tablet of Alka-Seltzer. Note that each different size particles was tested in the total of three trials.

The Experiment

Experiment The Fizz

Let The Rate Increase!

Conclusion The purpose of this experiment is to determine if changes reactant particle size will effects on the rate of a chemical reaction. As powdered tablet react with water, the rate of reaction are increases and take less time, which were supported by the recorded data. The central tendency of this data is measure by the mean. The mean for whole tablet of Alka-Seltzer after three trials is 50.8 +/- seconds; the mean for the tablet of Alka-Seltzer broken into half after three trails is 48.1 +/- seconds; the mean for the tablet of Alka-Seltzer broken into quarters after three trials is 42.1 +/- seconds; and the mean for the powdered tablet of Alka-Seltzer after three trials is 31.5 +/- seconds. The data did support my hypothesis, which was as the reactant particles are smaller (powdered tablet), the rate of chemical reaction will be faster. I may not have been able to accurately observe changes because thermometers are not always accurate. Temperature of the water and the glass are other factors that may also affected it, and so the measurement may not be so accurately measured.

Conclusion According to the data, the powdered tablet has the fastest rate of chemical reaction, which means tablets broken into quarters, tablets broken into half and whole tablet would not so much improve the rate of chemical reaction. For further studies, I suggest having more trials because when it comes to dissolving reactant, sometime the tablet may not have the same amount of concentrated particle in it. So with more trails for the experiment, there would be more confidence in the data.

Work Cited Olson, Andrew. "Big Pieces or Small Pieces: Which React Faster?" Science Fair Project Ideas, Answers, & Tools. 14 May 2008. Web. 18 Oct. 2011. <http://www.sciencebuddies.org/science-fair projects/project_ideas/Chem_p028.shtml?fave=no>. Orphardt, Charles E. "Chemical Properties." Elmhurst College: Elmhurst, Illinois. 2003. Web. 18 Oct. 2011. <http://www.elmhurst.edu/~chm/vchembook/105Achemprop.html>. Anissimov, Michael. "What Are Chemical Reactions?" WiseGEEK: Clear Answers for Common Questions. 2003-2011. Web. 18 Oct. 2011. <http://www.wisegeek.com/what-are-chemical-reactions.htm>. Aberdeen, Stan. "How to Identify the 6 Types of Chemical Reactions | EHow.com." EHow | How to Videos, Articles & More - Discover the Expert in You. | EHow.com. 1999-2011. Web. 18 Oct. 2011. <http://www.ehow.com/how_6208937_identify-6-types-chemical-reactions.html>. Miller, Kenneth R., and Joseph S. Levine. Prentice Hall Biology. Upper Saddle River, NJ: Pearson Prentice Hall, 2006. Print.