Experiment 1: The effects of temperature on rate

Ideas

  1. In order for a chemical reaction to occur, the particles, atoms or ions, which are REACTANTS, must physically come into contact with one another. Anything that increases the frequency of these encounters will increase the rate at which PRODUCTS are formed.
  2. The rate of a chemical reaction can be increased by increasing the temperature of these reactants.

My predictions:

Using hot water out of the tap, the rate of reaction will be ______times faster than at 0 degrees C.

Materials

Note: All experiments should be done using original formula effervescent Alka-Seltzer.

  • 6 Clear cups
  • Measuring cup
  • Thermometer, -20 degrees C to 110 degrees C
  • 3 Alka-Seltzer tablets
  • Stopwatch
  • Mortar and pestle
  • Source of hot water
  • Ice cubes
  • Graph paper

Procedure

A. Hot Water

  1. Run water from the hot tap until it is as hot as possible. Fill a clear glass with exactly 8 oz. of hot water.
  2. Use the thermometer to take the temperature and record it on your data sheet.
  3. Remove 1 Alka-Seltzer tablet from its package. Drop it into water. measure the time required for tablet to fully dissolve. Be prepared to start and stop on time. The reaction will take less than 15 seconds. Record the time.

B. Room Temperature Water

  1. Fill a clear glass with exactly 8 oz. of room temperature or lukewarm water.
  2. Use the thermometer to take the temperature and record it on your data sheet.
  3. Drop 1 Alka-Seltzer tablet into the water. Measure the time required for the reaction to be completed. Record the time.

C. Cold Water

  1. Fill a clear glass with 4 oz. of water and add enough ice to adjust the level to 8 oz. Stir the ice water for about 15 seconds so the temperature will come to equilibrium.
  2. Use the thermometer to take the temperature and record it on your data sheet. (Leave the ice cubes in the water!)
  3. Drop 1 Alka-Seltzer tablet into the water. Measure the time required for the reaction to be completed. Record the time.

Observations

Water Temperature - Time for Reaction to be Completed

Hot Tap _____ degrees C ______Seconds

Room temperature ______degrees C _____ Seconds

Ice Water _____ degrees C _____ Seconds

Analysis

Graph your data points (water temperature vs. time to fully dissolve) to show the effect of temperature on Rate of Reaction.

Summary

As the temperature increases, the rate (time it takes) of reaction ______.

Questions

  1. At a temperature of 10 degrees C, it would take ______seconds for 1 Alka-Seltzer tablet to react with 8 oz. of water.
  2. If the temperature is doubled from 20 degrees C to 40 degrees C, the time for the rate of reaction goes up / down (circle one) by approximately ______.
  3. Using hot tap water, the rate was ______times faster than at 0 degrees C.

Experiment 2: The Effect of Particle Size on Rate of Reaction

Ideas

The rate of a chemical reaction is affected by the physical size of the reactants. Decreasing the size of the particles which make up a given weight will increase the number of particles represented by the same weight. Smaller particle size results in an increase in the rate of reaction because the surface area of the reactant has been increased.

My predictions:

The powder will react ______times faster than the whole tablet.

Materials

Note: All experiments should be done using original formula effervescent Alka-Seltzer.

  • 3 Clear glasses
  • 3 Alka-Seltzer tablets
  • Mortar and pestle
  • Stopwatch

Procedure

A. Whole Tablet

  1. Fill a clear glass with exactly 8 oz. of room temperature or lukewarm water.
  2. Drop 1 whole Alka-Seltzer tablet into the water. Measure and record the time to dissolve.

B. Tablet Broken into ~8 Pieces

  1. Place 1 Alka-Seltzer tablet onto a sheet of paper and break into approximately 8 pieces of about equal size.
  2. Fill a clear glass with exactly 8 oz. of room temperature or lukewarm water.
  3. Slide broken tablet into the water from the sheet. Measure and record the time to dissolve.

C. Powdered Tablet

  1. Place 1 Alka-Seltzer tablet into mortar and grind to a fine powder.
  2. Transfer powder into a clear cup. (Note: It's important to have the powder in the cup before adding water.)
  3. Add 8 oz. of water to the glass. Measure and record the time to dissolve.

Observations

Particle Size Time for Reaction to be Completed

Whole Tablet ______Seconds

8 Pieces ______Seconds

Powder ______Seconds

Summary

a) As particle size decreases, the rate of reaction ______.

b) The rate of reaction for the powder was ______times faster than for the whole tablet.

Questions

  1. As particle size decreases, the total surface area of a reactant ______. As a result, the probability of interactions between atoms/ions ______, and the rate of reaction ______.
  2. Particle size appears to have ______(less or more) of an effect on the rate of reaction than temperature.

Experiment 3: Effect of Concentration of the Reactants

Ideas

  1. The rate of a chemical reaction depends on the frequency of the collisions between the atoms or ions of the REACTANTS.
  2. As the concentration of the reactants decreases the frequency of collisions decreases, and the RATE of the reactions slows down.

Investigations

In this investigation the rate at which aluminum replaces hydrogen from a solution of hydrochloric acid will be observed.

Materials

  • Test tube, 16 x 150mm
  • Test tube clamp
  • Beakers 100 ml, 1000 ml
  • Glass right angle bend
  • Rubber stoppers #0, 1 hole
  • Rubber tube 5/16" x 18"
  • Safety goggles
  • Aluminum metal
  • Hydrochloric acid, 1.0N HCl
  • Stopwatch or clock with second hand
  • Laboratory burner or a candle

Procedure

  1. Add strands of aluminum metal to 16 x 150 mm test tube. If any strands are longer than 1-1/2", bend them in half.
  2. Moisten the hole in the #0 rubber stopper and also one end of the glass right angle bend. Carefully insert the right angle bend into the stopper. Attach the rubber tube to the other end of the glass bend. Set the stopper assembly aside for now.
  3. Put on your safety goggles and gloves. Add just enough 1.0N hydrochloric acid, HCl, to the test tube to cover the aluminum metal, not over 1-1/2".
    Note: The aluminum metal has an oxide coating on its surface. This coating acts as a barrier between the metal and the acid, and it prevents the reaction from proceeding at its maximum rate.
  4. While holding the test tube at a 45 degree angle, gently warm the acid solution, do not boil (a candle could be used as the heat source). The warm acid will gradually remove the oxide coating and the rate of reaction between the aluminum and the acid will increase.
  5. Insert the stopper assembly into the test tube. Use the 400 ml beaker to support the test tube.
  6. Fill the 100 ml beaker with water. Place the free end of the rubber tube in the beaker.
  7. Observe the rate at which bubbles of hydrogen gas are escaping from the end of the rubber tube.
  8. As soon as the rate slows down to the point where it is possible to count each bubble as it rises to the surface, begin taking data. While one person keeps track of time, another counts bubbles released.

Count the number of bubbles released in 30 seconds. Repeat this process, counting the number of bubbles released in 30 second intervals, for a total of at least eight, 30 second time segments, or until the number of bubbles released during a 30 second interval has dropped to about 4. Record all data.