How Do You Rate?

Answer Key

Challenge #3: Lab Worksheet #2

(Station Two: Let’s Spread Out At This Station!)
Hypothesis: If the surface area of the chalk is smaller then the rate at which chalk reacts will decrease.
Observation Chart: Students will observe that the crushed chalk will react faster.

Conclusion:

1. a) Which beaker contained chalk with the greatest surface area? Two
   b) Why? Because the crushed chalk is in smaller pieces
2. Which beaker had the reaction that lasted the shortest time? Two
3. Write a statement to describe how the rate of a reaction is affected by changing the surface area of a substance.
   The greater the surface area (smaller pieces) the greater the rate of the chemical reaction.

Challenge #4: Lab Worksheet #3

(Station Three: This Is A Cool Station!)
Hypothesis: If the temperature of the water is higher then the rate at which an Alka-Seltzer tablet reacts will increase.
Observation Chart: Students will observe that the beaker containing the warm water will react the fastest. The slowest reaction occurs in the cold water.

Conclusion:

1. Which beaker contained the reaction that lasted the longest time? One
2. Which beaker contained the reaction that lasted the shortest time? Three
3. Write a statement to describe how the rate of a reaction is affected by changing the temperature of a substance.
   When the temperature of a substance increases, the rate at which it reacts also increases.