Key Concepts

Substances react chemically in characteristic waysA set of reactions deserve to be used to determine an unwell-known substance


Students will usage test liquids on various known powders and also observe their reactions. Then students will use these characteristic chemical changes to aid them identify an unrecognized powder.


Students will have the ability to identify and regulate variables to construct a test to recognize an unrecognized powder. Students will have the ability to define that a substance reacts chemically in characteristic ways and that these features deserve to be used to determine an unrecognized substance.

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Download the student task sheet, and distribute one per student when stated in the task. The activity sheet will certainly serve as the “Evaluate” component of each 5-E lesson plan.


Be certain you and the students wear properly fitting goggles. When utilizing tincture of iodine, follow all warnings on the label.

Materials for the Demonstrations

Baking sodaCornstarchCream of tartarTincture of iodineVinegarWater Universal indicatorGraduated cylinder or beaker2 droppers¼ teaspoon5 clear plastic cups3 Popsicle sticks

Materials for Each Group

Baking soda Baking powder Cream of tartar Cornstarch Water Vinegar Tincture of iodine Universal indicator 10 tiny plastic cups4 droppers8 Popsicle sticksTesting chart (laminated or spanned with wax paper)

Add iodine solution to baking soda and cornstarch to introduce the principle that various substances react chemically in characteristic means.

Materials for the Demonstration

Tincture of iodineBaking sodaCornstarchWaterGraduated cylinder or beaker2 Popsicle sticksDropper¼ teaspoon3 clear plastic cups

Teacher Preparation

Make a dilute tincture of iodine solution by including around 10 drops of tincture of iodine to 100 mL of water. Pour 50 mL of this solution into a clear plastic cup for this demonstration. Set the various other 50 mL aside for the student activity. Instructions for preparing the rest of the products for the student task are in the Explore section of this lesson. Place ¼ teaspoon corn starch in a clear plastic cup and also ¼ teaspoon baking soda in an additional cup. Do not tell students which powder is in each cup.


Tell students that you have a different powder in each cup. Both are white and also look aprefer, yet they are chemically various. Explore

Introduce the activity and also ask students exactly how they might test and also compare the 4 different powders through 4 different test solutions.

Tell students that in this task they will certainly test 4 various similar-looking powders with 4 different test options. The 4 powders are baking soda, baking powder, cream of tartar, and also cornstarch. The 4 test services are water, vinegar, iodine solution, and universal indicator. Explain that each powder will certainly react in a details way through each solution offered to test it. Each powder and also solution pair is one set of reactants. Let students understand that in some cases, no chemical reaction will certainly occur.

Students will certainly have to observe and also document the reactions the liquids have actually through each powder.

Have students look at the trial and error chart. Point out that the names of the four test services are on the left and the names of the different powders are on the optimal.

There is likewise one column for an unwell-known powder. Exsimple that after experimentation all four known powders and also recording their monitorings, you will certainly provide students an unrecognized powder to determine.

Ask students questions like the complying with to help them setup just how they will organize and also conduct their tests:

Do we need even more than one pile of each powder put on the chart? Yes. Each powder will be tested with each of the 4 options so there requirements to be four piles of each powder in the squares under its name.Should all the squares on the whole chart have actually samples of powder on them before you begin testing?It is finest if students place the 4 samples of one certain powder in its column on the testing sheet. Then students need to test that powder through each of the four solutions. Students should test a single powder via each of the test liquids prior to moving on to the next powder. Do the piles have to be around the same size?The size of the piles is not particularly important as long as sufficient powder is used to view a reactivity, if tbelow is one. When experimentation the unrecognized, try to make the piles of unrecognized around the exact same size as the piles of the various other powders.Should the variety of drops put on each pile be the same?The specific number of drops is not specifically important, although enough liquid must be added to watch if there is a reaction. When experimentation the unwell-known, be sure that the variety of drops used on the unrecognized is the very same as the number offered on the various other powders.How will certainly you remember your monitorings for each reaction? Students should record their monitorings automatically after a solitary test solution is added to a powder. These will certainly be recorded in a chart in the corresponding box on the activity sheet.

As an instance, overview the class as they test baking soda via water, vinegar, iodine solution, and universal indicator.

Question to Investigate

Can you use the characteristic means substances react to tell similar-looking substances apart?

Materials for Each Group

Baking soda in cupBaking powder in cupCream of tartar in cupCornstarch in cupWater in cupVinegar in cupTincture of iodine solution in cupUniversal indicator solution in cup4 Popsicle sticksTesting chart, either laminated or through a piece of wax paper over it4 droppers

Teacher Preparation

Each team will certainly need 5 labeled cups each containing among the powders and also four labeled cups each containing one of the four test remedies to complete all 3 of the activities in this leskid.

Prepare the powdersLabel 5 tiny cups Baking Soda, Baking Powder, Cream of Tartar, Cornstarch and Unknown.Place about ½ teaspoon of each powder right into its labeled cup. These powders will be tested in this activity.Place about ½ teaspoon of baking powder in the cup labeled unrecognized. Place the unknown cups aside. Students will certainly test this unwell-known powder after they have tested each of the “known” powders and also videotaped their observations.Prepare the Test SolutionsLabel 4 cups Water, Vinegar, Iodine, and Indicator. Use the iodine solution left over from the demonstration or make a new solution by including 5 drops of tincture of iodine to 50 mL of water. Place around 5 mL iodine solution in a small labeled cup for each team.Make a global indicator solution by including 5 mL of global indicator to 100 mL of water. Place about 5 mL (or 1 teaspoon) indicator solution in a little labeled cup for each team. Some indicator solution will be left over for the demonstration at the end of the leschild.Place about 5 mL of water and vinegar into their tiny labeled cups.


Use the end of a popsicle stick to place 4 equal piles of baking soda on the testing chart in the baking soda column. Let students recognize that they must not use all of the powder at this time. The remaining powder will be offered in the Extend percent of this leskid.

Add 5 drops of water to the first pile of baking soda. Record your monitorings in the chart on the task sheet.

Continue experimentation each pile of baking soda with a different test solution and also recording your monitorings.

Expected Results

There will certainly be no readjust via water, bubbling through vinegar, and also little bit to no adjust through the iodine or indicator remedies.

Ask students:

What did you observe once each test solution was included to a sample of baking soda?Baking soda bubbles with vinegar. There is no change with water or iodine solution. Students might see a slight shade adjust via the indicator solution. Exsimple to students that their results display them the characteristic set of reactions that baking soda has via these 4 test services. Would you expect each test solution to react through baking powder the very same way as it did with baking soda? No. Each powder need to have actually a different collection of reactions.

Have students conduct the tests on the continuing to be powders and also document their monitorings.


Test each of the powders with the test solutions the method you tested baking soda and document your monitorings.

Expected Results

Table 1. Expected student outcomes from combining test powders via test liquids.Test SolutionBaking SodaBaking PowderCream of TartarCornstarchWaterVinegarIodineIndicator
No changeBubblingNo changeNo change
Lots of bubbling that ends quicklyBubblingNo changeNo change
No changeBubbling, purpleOrangePurple
Greenish-blueBubbling, oarray alters to yellow via some greenDark oarray or pinkBrighter green, may have some orange

Give students the unrecognized powder and have actually them use their test services and monitoring chart to identify it.

Give each group the unknown powder. Explain to students that the unrecognized is one of the four powders they have actually tested and their job is to find out which one.

Ask students:

How can you test the unknown powder so that you might recognize it?Students need to realize that they will must test the unwell-known powder the very same method they tested all of the various other well-known powders and also compare the results. If the unknown powder reacts via each test solution the exact same means one of the well-known powders did, then these 2 powders need to be the same.

Question to Investigate

Can you use the characteristic means substances react to recognize an unwell-known powder?

Materials for each group

Unknown in cup1 Popsicle stickTesting sheet4 test solutions4 droppers

Note: The unwell-known is baking powder.


Place 4 samples of your group’s unrecognized powder in the “Unknown” column on the trial and error chart.Test the unknown through each test solution in the exact same way you tested each of the other powders.Compare the set of reactions for the unknown with those of the various other powders.

Expected Results

The unrecognized will react with each test solution the very same means that baking powder does because the unwell-known is baking powder.


Have students report the identity of the unrecognized and also discuss what evidence led them to their conclusion.

Tell students that they were able to usage their monitorings to identify the unrecognized bereason each powder had actually its very own collection of characteristic chemical reactions through the test options.

Ask students:

What is the identification of the unknown?Baking powder is the unknown.Which observations led you to your conclusion? The unknown reacted with each test solution the same means baking powder did.

Exordinary that each substance is made up of certain molecules which connect via the molecules in each test liquid in a characteristic method. Several of these interactions lead to a chemical reaction and also others carry out not. However before, each observation students made is based on the means the molecules of each powder connect with the molecules of each test solution.


Have students identify the 2 substances in baking powder that make it bubble once water is added.

Remind students that baking powder was the only substance that bubbled when water was included to it. Bubbling in a chemical reactivity is a sign that a gas is just one of the commodities. Tell students that baking powder is a mix of various powders—baking soda, cream of tartar, and also cornstarch. Two of these 3 react via one another and also develop a gas as soon as water is included. Students will need to test every one of the feasible combicountries of two powders with water. This way they deserve to figure out which 2 powders cause baking powder to bubble with water.

Concern to Investigate

Which two substances in baking powder react with one another and also develop a gas once water is added?

Materials for Each Group

Baking soda in a cupCornstarch in a cupCream of tartar in a cup3 Popsicle sticksToothpicksWax paperWaterDropper


Use separate popsicle sticks to area a tiny amount of 2 powders on a piece of wax paper. Use a toothpick to mix the powders.

Use a dropper to include around 5 drops of water to the unified powders and record your observations.

Repeat actions 1 and 2 till you have tested all 3 combicountries.

Expected results

The two linked powders that bubble with water are baking soda and cream of tartar.

Demonstprice that vinegar and also cream of tartar are both acids.

Point out that the mixture of baking soda and cream of tartar reacts with water to create a gas. Baking soda and also vinegar also react to create a gas. Exordinary that carbon dioxide gas is developed in both reactions. Tell students that cream of tartar and vinegar have actually something else in common that they will investigate in the next demonstration.

Question to Investigate

Will vinegar rotate universal indicator solution pink the way that cream of tartar does?

Materials for the Demonstration

Universal indicatorCream of tartarVinegar2 clear plastic cupsPopsicle stickDropper

Teacher Preparation

Use the indicator left over from the leskid. Use vinegar and cream of tartar left over from one of the student teams.


Pour around 25 mL of global indicator solution in 2 separate clear plastic cups. Add 2 or 3 drops of vinegar to one cup.Scoop up a small amount of cream of tartar via the tip of a popsicle stick and also add it to the various other cup. Swirl both cups.

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Expected Results

The indicator in both cups will certainly turn pink.


Tell students that the color changes of indicator solution have the right to tell you whether a substance is an acid or not. Because universal indicator turns pink when acids are added to it, we have the right to say that both vinegar and also cream of tartar are acids. When an acid reacts through baking soda, carbon dioxide gas is created.

Ask students

Why execute you think the baking soda and cream of tartar reaction is comparable to the baking soda and vinegar reaction?Cream of tartar and vinegar are both acids and connect via sodium bicarbonate in a similar method to develop carbon dioxide gas.