Name(s): ______

Signature(s): ______

Kinetic Theory in Action Lab

Background:

The wordkinetic comes from the Greek work kinetos, meaning “to move”. The energy an object has because of its motion is called kinetic energy. According to the kinetic theory, all matter consists of tiny particles that are in constant motion. The particles in a gas are usually molecules or atoms. Temperature is a measure of average kinetic energy, thus, some particles will have above average kinetic energy and others will have below average kinetic energy. Reactant particles with above average kinetic energy will be most likely to react upon collision.

Objective:

Students will be able to observe color changes in the chemical reactions of gases and interpret these changes in terms of kinetic theory.

Materials:

  • Petri dish
  • Ruler
  • Paper towels
  • Medicine dropper
  • Reaction surface with template
  • Chemicals – HCl, NaHSO3, KI, NaNO2, NH4Cl, and NaOH, BTB

Procedure:

  1. Add small drops of BTB (bromothymol blue) to the small circles in the pattern shown on the template. Be sure the drops do not touch one another.
  2. Mix 2-3 drops of each HCl and NaHSO3 in the center, large circle of the pattern.
  3. Quickly place the Petri dish over the grid to enclose the reaction (this means solid side up).
  4. Observe and record what happens in the data table for reaction 1.
  5. Carefully absorb the center mixture (large circle) of the previous experiment onto a cotton swab.
  6. To the large circle in the pattern, add 2-3 drops of NaOH and 2-3 drops of NH4Cl.
  7. Observe and record what happens in the data table for reaction 2.
  8. Clean off the entire reaction surface with a paper towel.
  9. Repeat the original experiment (steps 2-5) except use KI in place of BTB and mix sodium nitrite (NaNO2) with hydrochloric acid (HCl) at the center.
  10. Observe and record what happens in the data table for reaction 3.

Results:Record your observations in detail for each reaction in the table below. You may use words or images to describe what you see.

Reaction 1 / Reaction 2 / Reaction 3

Analysis:

  1. Translate the following word equation into a balanced equation: Sodium hydrogen sulfite reacts with hydrochloric acid to produce sulfur dioxide gas, water, and sodium chloride.

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  1. Ammonium chloride reacts with sodium hydroxide to produce ammonia gas, water, and sodium chloride. Write and balance a chemical equation to describe this reaction.

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  1. Write and balance an equation: Sodium nitrite reacts with hydrochloric acid to produce nitrogen monoxide gas, water, sodium nitrate and sodium chloride.

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  1. The BTB changed even though you added nothing to it. If the mixture in the center circle produced a gas, would this explain the change in the drops of BTB? Use kinetic theory to explain your answer.
  1. Predict the effect of the size of the BTB drops on the rate at which they change. Explain your results in terms of kinetic theory.
  1. Predict the effect of the temperature of the reactants on the rate at which they change. Explain your results in terms of kinetic theory.