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Lesson vi.five

A Catalyst and the Rate of Reaction

Cardinal Concepts

• A goad is a substance that tin can help the reactants in a chemical reaction react with each other faster.
• A catalyst does not really get function of the products of the reaction.

Summary

Students scout a video and exercise a quick activity to see that a catalyst can increase the rate of the breakdown (decomposition) of hydrogen peroxide. Students will and so utilise salt every bit a catalyst in a reaction betwixt aluminum foil and a solution of copper II sulfate. Students will be introduced to the concept that a catalyst increases the rate of a chemical reaction but is not incorporated into the products of the reaction.

Objective

Students will be able to define a catalyst every bit a substance that increases the rate of a chemical reaction but is not incorporated into the products of the reaction.

Evaluation

Download the educatee activity sheet, and distribute one per educatee when specified in the activeness. The activity sheet will serve as the "Evaluate" component of each five-East lesson plan.

Safety

Be sure you lot and the students wear properly fitting goggles. When using hydrogen peroxide, follow all warnings on the label. After students have conducted the activity with the copper II sulfate solution and aluminum foil, allow the contents of the cup to evaporate. Put the small-scale amount of solid in a paper towel and dispose in the trash or use a disposal method required by local regulations.

Materials for Each Group

• Graduated cylinder (50 mL or 100 mL)
• Hydrogen peroxide (3%)
• Yeast
• two Popsicle sticks
• Detergent solution
• Dropper
• Small cup
• Clear plastic cup
• Copper Ii sulfate solution (in cup)
• Salt
• Aluminum foil (v cm × 5 cm)
• Thermometer

Notes virtually the Materials

Copper II sulfate is available from diverse chemical suppliers including Sargent Welch, Product #WLC94770-06 or Flinn Scientific, Product #C0110.

1. Show students two demonstrations and have them look for evidence that a gas is produced in the chemical reactions.

   Tell students that you will show them video of two demonstrations where water vapor and oxygen gas are produced in the exact aforementioned chemic reaction. Because gases are invisible, ask students to watch closely for evidence that a gas is produced.

   Project the video Elephant'south Toothpaste.

   The foaming shows that gases (oxygen and water vapor) are being produced very chop-chop. The corporeality of foam produced in a period of time is a way of measuring the rate of the reaction.

   Project the video Genie in a Bottle.

   The steam coming out of the bottle is h2o vapor that is condensing as it leaves the bottle. Oxygen is also leaving the canteen but it is invisible.

   Inquire students:

   How could yous tell that a gas is produced in the chemic reaction?

   The foaming in the elephant toothpaste sit-in ways that a gas is produced. Production of a gas is a clue that a chemical reaction has occurred. The water vapor in the genie-in-a-canteen sit-in besides shows the production of a gas.

   Tell students that this lesson is about speeding upward chemic reactions. Some reactions occur very slowly, but chemicals called catalysts can be added in gild to make them happen faster. Both of these demonstrations relied on a catalyst.

2. Depict how the decomposition of hydrogen peroxide produced oxygen gas in both of the videos.

   Tell students that both of the demonstrations use a thirty% hydrogen peroxide solution. Typically the hydrogen peroxide y'all can by at the store is only 3% hydrogen peroxide. Explain to students that the chemical formula for hydrogen peroxide is H₂O₂. Indicate out that hydrogen peroxide is not very stable and breaks down into water and oxygen on its own. This kind of change is a chemic reaction called decomposition. The decomposition of hydrogen peroxide is ho-hum and is not usually noticeable.

   Project the image Decomposition of Hydrogen Peroxide.

   Explain that hydrogen peroxide decomposes to course water and oxygen according to this chemic equation:

   Tell students that this chemical reaction happens on its own, and that even the energy from the light in a room can cause hydrogen peroxide to decompose faster. This is why hydrogen peroxide is sold in opaque containers.

   Tell students that in the video, a substance (potassium permanganate or manganese dioxide) was used to brand the decomposition of hydrogen peroxide happen a lot faster. Fifty-fifty though it fabricated the reaction become faster, the substance itself didn't modify during the reaction. A substance that increases the rate of a reaction but does not become office of the products of the reaction is called a catalyst.

   Ask students:

   Your instructor showed you a sit-in where a catalyst is added to hydrogen peroxide and a great deal of oxygen gas is produced. If the catalyst is involved in the chemical reaction, why isn't it included as a product in the chemical equation?

   A catalyst does not cease up in the products and so is non included in the chemical reaction.

   What does a catalyst exercise in a chemic reaction?

   Catalysts assist a reaction happen faster only practise not change themselves during the reaction.

   Give Each Student an Activity Canvas.

   Students will record their observations and reply questions about the action on the activity canvass. The Explain It with Atoms & Molecules and Take It Further sections of the activity canvas will either be completed as a class, in groups, or individually, depending on your instructions. Await at the teacher version of the action canvas to find the questions and answers.

3. Have students use yeast to catalyze the decomposition of hydrogen peroxide.

   Question to Investigate

   Can another substance catalyze the decomposition of hydrogen peroxide?

   Materials for Each Group

   • Graduated cylinder
   • Hydrogen peroxide (3%)
   • Yeast
   • Popsicle stick
   • Detergent solution
   • Dropper

   Teacher Preparation

   Make a detergent solution past adding 1 teaspoon of liquid dish detergent to 2 tablespoons of h2o. Divide this detergent solution every bit into one modest cup for each group.

   Procedure

   1. Add x mL of hydrogen peroxide to a graduated cylinder. Add i drop of detergent solution. Swirl gently and lookout the solution for any bubbles.

      Explain to students that the detergent is added but to make bubbles if whatsoever gas is produced. Since the breakdown of hydrogen peroxide produces oxygen gas, bubbles shows that the hydrogen peroxide is breaking down or decomposing. The lack of bubbling shows that not much oxygen gas is being produced.

   2. Use the cease of a popsicle stick to add a pocket-size amount of yeast to the hydrogen peroxide in the graduated cylinder and swirl.

      
   3. Identify the graduated cylinder on the tabular array and lookout man for whatever bubbling.
   4. Hold the graduated cylinder to come across if at that place seems to exist whatsoever change in temperature.

   Expected Results

   Before the yeast is added, there is no observable bubbling. Afterward the yeast is added, bubbles will cause foam to move up the graduated cylinder. Also, the graduated cylinder should feel a little warmer because the decomposition of hydrogen peroxide releases free energy. Energy changes in chemic reactions will exist investigated in more detail in Affiliate half-dozen, Lesson vii.

4. Discuss student observations.

   Ask students:

   What clues did you have that a chemic reaction occurred in this activity?

   Bubbles. Tell students that a change in temperature is also a sign that a chemic reaction may be occurring. Endothermic and exothermic chemical reactions will be addressed in Chapter half dozen, Lesson seven.

   What is the catalyst in this activity?

   A substance in yeast.

   What bear witness do you have that hydrogen peroxide decomposed faster when y'all added yeast?

   Bubbles of oxygen gas were produced afterward the yeast was added.

   When you write the chemic equation for this reaction, should yeast be included on the production side of the chemical equation?

   Explicate to students that the catalyst in the yeast does not end up in the products but is a substance that helps the decomposition happen faster. Sometimes a catalyst is written above or below the pointer in a chemic equation, simply it is never included with the reactants or products.

   In full general, catalysts work by providing a place where reactants can come together to react. Explain to students that cells in yeast and other organisms comprise a catalyst called catalase. Through normal cell processes, living things produce hydrogen peroxide in their cells. But hydrogen peroxide is a poison so the cells need a way to break it down very quickly. Cells incorporate catalase, which breaks down hydrogen peroxide at a very fast charge per unit. A unmarried molecule of catalase tin can catalyze the breakdown of millions of hydrogen peroxide molecules every second.

   Students may go on to explore the issue of catalase on hydrogen peroxide by adding a piece of raw fresh potato to a pocket-size amount of hydrogen peroxide.

5. Accept students identify the changes that occur when copper 2 sulfate reacts with a piece of aluminum foil.

   Note: This is a reaction between copper II sulfate and aluminum. The copper is called "copper II" because copper tin brand dissimilar types of ions. It tin can lose i electron and be just Cu⁺ or information technology can lose 2 electrons and be Cu²⁺. This type of copper ion is called copper II. As well the "sulfate" in copper II sulfate is besides an ion. This ion is made up of more than one atom. It is one of the polyatomic ions discussed in Chapter 4, Lesson three. The sulfate ion is fabricated up of a sulfur atom bonded to four oxygen atoms and is treated every bit one ion (SO_iv ²⁻).

   There are several interesting aspects of the reaction between copper 2 sulfate and aluminum, just information technology is dissimilar from the other reactions students have seen so far. In this reaction, the motility of electrons, rather than unabridged atoms, ions, or molecules, causes the reaction to occur. This blazon of reaction is called an oxidation/reduction reaction. This particular reaction is fun to do because information technology is exothermic, generates a gas, and copper metal appears as aluminum metal disappears.

   Salt can exist considered a catalyst in the reaction but has a different office than most catalysts. Copper Two sulfate and aluminum react very slowly because aluminum is coated with a very thin layer of tarnish (aluminum oxide). This reaction can be sped upward if the layer of aluminum oxide is removed or compromised. Adding salt does this and allows electrons from the aluminum to react with the copper ions in the solution, causing them to go copper metal.

   Question to Investigate

   What is the catalyst in the following activity?

   Materials for Each Group

   • Copper II sulfate solution (in loving cup)
   • Clear plastic cup (empty)
   • Salt
   • Piece of aluminum foil
   • Thermometer
   • Popsicle stick

   Instructor preparation

   Make a copper II sulfate solution past calculation twenty 1000 of copper II sulfate to 200 mL of water. Pour about 25 mL of copper Two sulfate solution into a cup for each group. Cut aluminum foil into pieces big enough to comprehend the bottom of a cup (nigh 5 cm long × 5 cm wide).

   Procedure

   1. Place the piece of aluminum foil in an empty cup. Use your fingers or a Popsicle stick to push the foil firmly downwardly and then that it lays flat and covers the bottom of the cup.
   2. Add all of the copper II sulfate solution to the loving cup with the aluminum foil.
   3. Gently swirl the solution for a few seconds and let it stand up still. Watch the aluminum for any bubbles or color change.

   4. Utilise your Popsicle stick to identify a small amount of salt in the copper II sulfate solution. Gently swirl the solution for a few seconds and allow information technology stand still. Watch for any bubbles or colour change.

      
   5. Carefully place a thermometer in the cup and come across if the temperature changes.

   Expected Results

   Before the common salt is added, at that place is no bubbling or color change. Afterward the common salt is added, the color turns light-green and bubbles begin to form on the aluminum. Presently, brownish fabric (copper) begins to form on the aluminum. The bubbles becomes more than vigorous and the solution loses its blue color equally the aluminum disappears and more than copper is produced. The solution as well gets warmer.

6. Discuss student observations.

   Ask students:

   How do yous know that a chemical reaction occurs when a piece of aluminum foil and sodium chloride is placed in copper II sulfate solution?

   In that location was bubbling, a color change, an increase in temperature, and a different solid was formed.

   What is the catalyst in this action?

   Salt.

   How is adding table salt to the aluminum similar to adding yeast to the hydrogen peroxide?

   Both tin be seen as catalysts. Calculation yeast helps the hydrogen peroxide decompose faster and calculation salt helps the aluminum react with the copper II sulfate.

   Tell students that the blueish solution contains copper ions (Cu2+). Adding salt to the solution helps remove a layer of tarnish from the slice of aluminum that was in the solution. This exposes some aluminum and allows electrons from the aluminum to react with the copper ions. These negative electrons are attracted to the positive copper ions. When the electrons join with the copper ions, the ions become neutral copper atoms and look similar copper metal in the solution. As the aluminum loses its electrons, information technology becomes aluminum ions and goes into the solution and seems to disappear.

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Source: https://www.middleschoolchemistry.com/lessonplans/chapter6/lesson5

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