Chemical Weathering Lab

Purpose/Problem Statement: How does temperature affect the rate of chemical weathering?

Hypothesis/Prediction Write a hypothesis using the IF, THEN, BECAUSE format.

Identification of Variables: Manipulated: The temperature of water. Responding: The amount of time to dissolve. Controlled: The amount of water The tablet size

Materials: beaker thermometer water 4 antacid tablets stopwatch

Procedure: Add 200 mL of ice water to a beaker Record the starting temperature of the water in the Data Table. Remove the thermometer from the beaker. Drop an antacid tablet into the beaker. Start the stopwatch as soon as the tablet enters the water. Stop the stopwatch when the tablet has completely dissolved and no traces of the tablet are visible. (Don’t wait for the bubbling to stop.) Record the time in the Data Table. Repeat Steps 2–3 three more times, for room temperature, warm, and hot water. The total volume of water should always be about 200 mL.

Data Table 1: Dissolving Times Water Type Temperature (°C) Dissolving Time (seconds) Cold Water Room Temperature Water Warm Water Hot Water

Make a bar graph of your results. [water type vs. dissolving time]. Graph & Conclusion Make a bar graph of your results. [water type vs. dissolving time]. Write your conclusion following the format on the “How to write an 8th grade lab write-up” handout.

Analysis 1. Analyzing Data: At which temperature did the antacid tablet dissolve most rapidly? At which temperature did the antacid tablet dissolve most slowly? 2. Drawing Conclusions: What is the relationship between temperature and the rate at which antacid tablets dissolve in water? 3. Formulating Hypotheses: Based on your observations, form a hypothesis about the relationship between temperature and the rate of chemical weathering. 4. Predicting: What would your results have been if you had ground each tablet into a fine powder before dropping it into the water? Would your conclusion be the same or different? Explain. 5. Inferring: Would a limestone building weather more rapidly in Homer, Alaska, or in Honolulu, Hawaii? (Both cities receive about the same amount of precipitation in an average year.) Explain your reasoning.