Name: ___________________________ Date ...



Name: __________________________________________ Date: _________________

Investigating Alka-Seltzer Reaction Rates

EXPERIMENTAL DESIGN LAB

Benchmark:

SC.8.N.1.1 - Define a problem from the eighth grade curriculum using appropriate reference materials to support scientific understanding, plan and carry out scientific investigations of various types, such as systematic observations or experiments, identify variables, collect and organize data, interpret data in charts, tables, and graphics, analyze information, make predictions, and defend conclusions.

Objectives:

• Design and conduct a scientific investigation to demonstrate evidence of scientific thinking and/or problem solving.

• Interpret and analyze data to make predictions and defend conclusions.

• Explain the value of hypotheses, even if they turn out not to be supported by the data.

Background:

Alka-Seltzer® is an effervescent tablet. Effervescence is a term used to describe the bubbly fizzing that results when you plop an Alka-Seltzer® tablet into water. As the tablet begins to dissolve in water the following chemical reaction occurs between the ingredients in the Alka-Seltzer® tablet:

H3C6H8O7 + 3NaHCO3 3H2O + 3CO2 + Na3C6H5O7

Citric Acid Baking Soda Water Carbon Dioxide Sodium Citrate

Chemical reactions occur as a result of collisions between molecules. The faster the molecules in the citric acid and baking soda collide with one another, the faster the chemical reaction takes place and produces water, carbon dioxide and sodium citrate.

Alka-Seltzer® is an antacid used to relive the discomfort associated with heartburn and indigestion. For over 74 years, the makers of Alka-Seltzer® have made the following claim about their product:

“When you feel acid indigestion or heartburn with pain, turn to Alka-Seltzer® for SPEEDY relief. Alka-Seltzer is an antacid pain reliever that gently breaks up and dissolves away the full feeling of acid indigestion FAST.”

The purpose of this lab is to design a controlled experiment that investigates the variables that affect the rate of the Alka-Seltzer® chemical reaction.

Question:

How can the SPEEDY Alka-Seltzer® reaction be made even speedier?

Control Group - Record the reaction time for a complete ¼ tablet of Alka-Seltzer®, placed in 20 mL of room-temperature (25 °C) water:

Reaction time - _________________ seconds

Determine the variables that might increase the rate of the reaction:

o ______________________________________________________________ (Investigated by Group #1)

o ______________________________________________________________ (Investigated by Group #2)

o ______________________________________________________________ (Investigated by Group #3)

o ______________________________________________________________ (Investigated by Group #4)

o ______________________________________________________________ (Investigated by Group #5)

Hypothesis:

Use the “If, then, because” statement format below to write a hypothesis for the experiment you will be conducting.

If ______________________________________________________________ then _____________________________________________________________

because __________________________________________________________________________________________________________________________

Materials (per group):

• 1-2 Alka-Seltzer® tablets (pre-cut into quarters)

• Film canister

• Dissecting pan

• Graduated cylinder

• 100 mL of water

• Stopwatch

Procedure:

1) As a group, use the table below to plan and design an experiment to test your hypothesis. Be sure that your experiment includes all of the following essential components:

o Test Variable (Independent Variable) ___________________________________________________________________________________

o Outcome Variable (Dependent Variable) ________________________________________________________________________________

o Constant Variables ________________________________________________________________________________________________________

|Variables |Control |Trail 1 |Trail 2 |Trail 3 |

|Concentration of | | | | |

|Alka-Seltzer | | | | |

|Volume of Water | | | | |

|Temperature of Water | | | | |

|Surface Area of | | | | |

|Alka-Seltzer | | | | |

|Shaking the Canister | | | | |

2) As a group, set up and execute your experiment with 3 variations of the variable you are testing.

Use the table (on the next page) to record your data.

3) Provide a numbered list of the steps you took to execute your experiment:

Data: Share your results with the rest of your class my inputting your data in the class data table.

|Alka-Seltzer® Reaction Rate |

|Group #1 |

| | | | | |

Analysis:

1) Based on the data collected in this experiment, which 3 variables resulted in the speediest Alka-Seltzer® reaction?

1.

2.

3.

2) Does the data collected in your experiment support your original hypothesis? If so, explain how. If the data does not support your hypothesis, explain why this hypothesis is still valuable.

Conclusion:

-----------------------

Claim:

Make a CLAIM based on what you observed in the experiment you performed today.

Evidence:

Support your claim using EVIDENCE you collected in your experiment.

Reasoning:

Use science concepts to provide REASONING for why the evidence you presented supports your claim.

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