This laboratory session is designed to compare the reactivity and behavior of magnesium in two different forms—powder and ribbon—when reacting with hydrochloric acid (HCl). By measuring the reaction time and temperature changes, students can delve into the concepts of reaction surface area, reaction rate, and activation energy.
Educational Goals
- Surface area and reaction speed: Students will learn how the difference in contact surface area between magnesium powder and ribbon affects the reaction speed, with the powder’s larger surface area typically resulting in a faster reaction.
- Activation energy: The experiment highlights the role of activation energy in chemical reactions and demonstrates how the physical form of reactants can influence this critical energy threshold.
- Control of chemical reactions: Emphasizes the significance of controlling experimental variables to accurately compare the reactivity of different forms of magnesium with HCl.
- Thermodynamics and kinetics: Through temperature measurements, students will explore thermodynamics and chemical kinetics concepts, observing the heat release and the rate at which reactions occur.
By conducting a comparative analysis of magnesium powder and ribbon reacting with hydrochloric acid, students gain insights into the factors that influence reaction rates. This laboratory underscores the importance of surface area, activation energy, and precise control and measurement in studying chemical reactions, enhancing students’ understanding of fundamental chemistry principles.
Protocol
Part 1 : Reaction of magnesium powder with hydrochloric acid
- Measure 100 mL of hydrochloric acid (HCl) 1M using the graduated cylinder.
- Pour the contents of the graduated cylinder into the calorimeter.
- Immerse the tip of the digital thermometer in the liquid to take its temperature.
- The initial temperature of the water will appear in the results table.
- Weigh approximately 0.6g of magnesium (Mg) powder.
- Pour the contents of the weighing boat into the calorimeter.
- Put the lid on the calorimeter.
- Insert the digital thermometer into the calorimeter lid.
- Start the stopwatch.
- Activate the green button of the stirrer on the calorimeter lid.
- The graph of temperature as a function of time is on the tablet (graph tab).
- Note the final temperature when the reaction ends (after approximately 30 to 60 seconds).
- Stop the stopwatch.
- The results are found in the results tab on the tablet.
- Stop the agitator by pressing the red button.
- Remove the thermometer from the calorimeter lid.
- Remove the calorimeter lid.
- Empty the contents of the calorimeter into the recovery tank.
- Rinse the calorimeter with distilled water and empty its contents into the recovery tank.
- Rinse the graduated cylinder with distilled water and empty its contents into the recovery tank.
- Reset the stopwatch.
Part 2 : Reaction of magnesium ribbon with hydrochloric acid
- Measure 100 mL of hydrochloric acid (HCl) 1M using the graduated cylinder.
- Pour the contents of the graduated cylinder into the calorimeter.
- Immerse the tip of the digital thermometer in the liquid to take its temperature.
- The initial temperature of the water will appear in the results table.
- Weigh approximately 0.6g of magnesium (Mg) ribbon.
- Pour the contents of the weighing boat into the calorimeter.
- Put the lid on the calorimeter.
- Insert the digital thermometer into the calorimeter lid.
- Start the stopwatch.
- Activate the green button of the stirrer on the calorimeter lid.
- The graph of temperature as a function of time is on the tablet (graph tab).
- Note the final temperature when the reaction ends (at approximately 3 minutes) stop the stopwatch.
- Stop the stopwatch.
- The results are found in the results tab on the tablet.
- Stop the agitator by pressing the red button.
- Remove the thermometer from the calorimeter lid.
- Remove the calorimeter lid.
- Empty the contents of the calorimeter into the recovery tank.
- Rinse the calorimeter with distilled water and empty its contents into the recovery tank.
- Rinse the graduated cylinder with distilled water and empty its contents into the recovery tank.
- Reset the stopwatch.
- Note the time required until the end of the reaction, determined by the stabilization of the temperature. Compare to the reaction from part 1 carried out with magnesium powder.
Anticipated Outcomes
Part 1
- 0.63 g of Mg(s) powder will produce 440 kJ/mole of Mg.
- In HCl 1 M, the temperature increase will be 25℃, in about 84 seconds.
Part 2
- 0.55 g of Mg(s) ribbon will produce 440 kJ/mole of Mg.
- In HCl 1 M, the temperature increase will be 22℃, in about 140 seconds.
Summary of Assignment by Grade Range
Grades 3-5 (Ages 8-10)
- Focus: Basic introduction to reaction rate and surface area concepts.
- Activities: Observing reactions of magnesium powder and ribbon with hydrochloric acid, noting simple differences in reaction speed, basic safety instructions.
Grades 6-8 (Ages 11-13)
- Focus: Intermediate understanding of surface area effects on reaction rate and basic thermodynamics.
- Activities: Conducting reactions with magnesium powder and ribbon in hydrochloric acid, measuring reaction times and temperature changes, comparing reactivity of different forms of magnesium, following detailed safety protocols.
Grades 9-12 (Ages 14-18)
- Focus: Advanced understanding of reaction kinetics, surface area effects, and thermodynamics.
- Activities: Accurately conducting reactions with magnesium powder and ribbon, measuring and recording reaction times and temperature changes, analyzing the impact of surface area on reaction rate and activation energy, detailed recording and interpretation of results, adhering to advanced safety protocols, reinforcing concepts of chemical kinetics and thermodynamics.
Laboratory essentials
Instruments
- Beaker (1000ml)
- Calorimeter
- Electronic Scale
- Graduated Cylinders (70ml & 250ml)
- Spatulas
- Thermometers
- Timer
- Tweezers.
Products
- HCl 1 M (solution)
- Magnesium (powder)
- Magnesium (ribbon)