Chemical Reactions (Kimberly Tafoya)

Research Question and Hypothesis

The goal of this project is to measure the effect of temperature on the rate of a chemical reaction.

The rate of a chemical reaction is determined by a large number of factors. Some reaction rates do not change under any conditions. These reactions typically occur either very slowly or extremely rapidly. However, most reactions can be affected by changing reaction conditions. In this lab activity we will study a single reaction and determine how various conditions affect the reaction speed.

Standards

Reaction Rates

8. Chemical reactions depend on factors that influence the frequency of collisions of reactant molecules. As a basis for understanding this concept:

c) Students know how reaction rates depend on such factors as concentration, temperature, and pressure.

Experimental Design

Independent variable

The independent variable is time in seconds. Students will measure the independent variable with a stopwatch while observing the reaction and identifying when the reaction is complete.

Dependent variables

The dependent variable is temperature. The dependent variable will be measured using a constant temperture for each trial of cold water, room temperature water and hot water.

Series

Study the effect of temperature as a function of time at various temperatures and with various particle sizes.

Constants and Controls

Constants- The amount of distilled water is the same as well as the amount of Alka-Seltzer Tablet.

Control- The whole size Alka-Seltzer Tablet

Materials

A chemical reaction occurs when the reacting particles have an effective collision that results in the formation of new particles. If the number of effective collisions can be controlled then the rate of reaction can be controlled. Some of the ways that can be used to control the number of collisions include 1) changing the concentration of the reactants, 2) changing the surface area of the reactants, and 3) changing the speed at which the particles are moving. Remember, temperature affects the speed at which particles move.

In order to study the effect of each change separately, this experiment will be dividing into three parts. Each part varies only one of the conditions: reactant concentration, reactant surface area, or temperature. Each variable has an effect on the reaction rate, which will be measured. Alka-Seltzer tablets will combine with water to produce a rate of reaction. The rate of the reaction is easily noted because the Alka-Seltzer tablet will be completely used up and fizzing will cease.

Equipment: 2- 50 mL Beakers Reagents: 3 Alka-Seltzer Tablets

Hot Plate tap or room temperature water

Pestle and Mortar warm water

Stopwatch ice water

Procedures

1. Score an X on the back and break each of your tablets into FOUR pieces for the 8 (minimum) trials you will be conducting. (You have been given enough to do 12 trials – record ALL results)

2. Add approximately 20mL of room temperature water into your canister (about 2/3 full) and drop one-fourth tablet into the water inside the canister, quickly cap and begin timing the reaction. Upon completion of the reaction, record and time in seconds. Dispose of the used solution in the sink to begin each trial.

3. Repeat this procedure for Trial 2 but now break the quarter tablet broken into pieces. For Trial 3 grind the quarter tablet into power with the Mortar and Pestle.

4. Upon completion of the 3 trials with tap water, repeat your experiments (trial 4, 5, 6) this time with ice water and then finally with warm, not boiling water (7, 8, 9). Record your data in the data table.

Sample data and graphs

Students would then go to Create A Graph and create a graph using the data from this activity.

Analysis & Conclusions

Review your data and write a conclusion statement in your own words. State the relationships you observed regarding the rate of reaction of the experiments done with room temperature, ice and warm water as well as the relationships between the particle size, whole, pieces or ground powder. What would be the optimum conditions for the highest reaction rate?

Photos & Movies

References

Create A Graph http://nces.ed.gov/nceskids/createagraph/default.aspx

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