Key Concepts

The ion or molecules in two solutions can react to kind a solid.A solid created from two options is called a precipitate.

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Students will combine two clean colorless solutions (baking soda solution and also calcium chloride solution) and see the formation of a solid and a gas. Students will analyze the chemical equation for the reaction and see the all atom in the reactants end up in the products. They will certainly make the connection in between the chemistry equation and also the real substances and also see that the solid and also gas produced in the really reaction are also in the assets of the equation.


Students will be able to explain that for a chemistry reaction to take place, the reaction interact, bond between details atoms in the reactants space broken, the atom rearrange, and brand-new bonds between the atoms are developed to make the products. Students will also be able to describe that this an interpretation applies to the production of a solid called a precipitate.


Download the student activity sheet, and also distribute one per student when specified in the activity. The activity sheet will serve together the “Evaluate” ingredient of each 5-E lesson plan.


Copper II sulfate is obtainable from miscellaneous chemical suppliers, including Sargent Welch, Product #WLC94770-06 or Flinn Scientific, Product #C0110. Follow all safety precautions concerning use, storage, and disposal that copper II sulfate and sodium carbonate. Salt carbonate is Product #WLC94291-06 or #S0052.

Materials because that the Demonstrations

Sodium carbonateEpsom salt (magnesium sulfate)2 clear plastic cupsTest tubeWaterCopper II sulfateHousehold ammoniaHydrogen peroxide (3%)Graduated cylinder2 droppers

Materials because that Each Group

Baking sodaCalcium chloride WaterGraduated cylinder measure spoon (½ teaspoon) or balance2 clear plastic cupsMasking tapePen

About the Materials

Copper II sulfate is obtainable from assorted chemical suppliers, consisting of Sargent Welch, Product #WLC94770-06 or Flinn Scientific, Product #C0110. Monitor all safety and security precautions regarding use, storage, and also disposal of copper II sulfate.


Do a demonstration by combining two clear colorless remedies that produce a white solid and also introduce the hatchet precipitate.

Materials because that the Demonstration

Magnesium sulfate (Epsom salt)Sodium carbonateWater2 clean plastic cups1 tablespoon1 teaspoon

Teacher Preparation

Pour 100 mL of water in one clean plastic cup and include 10 g (about 1 tablespoon) the magnesium sulfate. Stir till the equipment is clear. To water 50 mL the water in an additional clear plastic cup and add 5 g (about 1 teaspoon) of sodium carbonate. Stir until the solution is clear.



Have students combine two liquids come observe another precipitate.

Question come Investigate

How do you understand when a precipitate is developed in a chemical reaction?

Materials for Each Group

Baking sodaCalcium chloride WaterGraduated cylinder measuring spoon (½ teaspoon) or balance2 clean plastic cupsMasking tapePen

Note: If girlfriend would prefer students to exercise using a balance to sweet grams, have them weigh 2 grams each of baking soda and also calcium chloride.


Use masking tape and a pen to label 2 plastic cup baking soda solution and also calcium chloride solution. Use a i graduated cylinder to add 20 mL of water to every cup. Include 2 g (about ½ teaspoon) the calcium chloride come the water in its labeled cup. Swirl till as much of the calcium chloride dissolves as possible. Include 2 g (about ½ teaspoon) that baking soda to the water in its labeled cup. Swirl till as much of the baking soda dissolves together possible. There may be some undissolved baking soda staying in the bottom of the cup.

Carefully pour the baking soda solution right into the calcium chloride solution. Try not to pour in any undissolved baking soda. Observe.


Expected Results

Bubbling and also a white precipitate appear.

Discuss student observations.

Ask students:

What did friend observe once you mixed the baking soda solution and also the calcium chloride solution?The remedies bubbled and small white corpuscle of heavy formed. Did you watch a precipitate? Yes. The white particles showed up after the two solutions were combined.Do friend think this to be a chemical reaction? Yes. Why?The two substances the were an unified were liquids and also the substances the were produced were a solid and a gas. These products seem come be different from the reactants.Explore

Separate the commodities to present that the precipitate is a solid.

Ask students:

How perform you think we could separate the precipitate from the various other products?

Question come Investigate

Can you different the calcium lead carbonate from the remainder of the products?

Materials because that Each Group

Coffee filter or record towelTall clean plastic cup


Use a large enough coffee filter (or paper towel) so the you can push it about ⅓ that the method into the cup and also still have enough left to hold it about the external of the cup.

While hold the coffee filter in place, to water the commodities into the facility of the coffee filter.

Allow the liquid to drip with the filter. This may take a while. Collection the precipitate beside and enable the water come evaporate.

Expected results

A white hard will remain in the coffee filter. After the water evaporates, the calcium carbonate will be a white powder.

Note: If you’d like to separate the sodium chloride from the water that flowed with the filter, pour the liquid into a clean empty cup and allow the water to evaporate because that a couple of days. Together the water evaporates, student will begin to check out cubic-shaped salt crystals creating in the solution. Eventually only salt crystals will stay in the cup.

Ask students:

What is the heavy white problem on the paper?Calcium carbonate (chalk).Is filtering the end the calcium lead carbonate and permitting the water to evaporate a chemical adjust or a physical change? physics change. Why? this substances were already present in the water, so no new chemicals space made. What evidence was there that a chemical reaction emerged when you merged baking soda solution and also calcium chloride solution? A gas and also a white solid to be formed

Confirm that a chemistry reaction take it place

Ask students:

How might we to compare the precipitate come the reaction to be sure that the precipitate is actually different from both of them?Do a solubility check on all 3 substances.

Question to Investigate

Is the solubility of the precipitate different than the solubility that baking soda and also calcium chloride?

Ask students:

How must we set up the solubility test?

Should we usage the exact same amount of each substance?YesShould we use the exact same amount of water?Yes

Materials for Each Group

Dry precipitate on paper towelBalance3 tiny plastic cupsGraduated cylinderGraduated cylinderPopsicle stick (optional)Calcium chlorideBaking sodaWater


Label 3 cup sodium bicarbonate, calcium chloride, and also precipitateUse a spoon or popsicle stick to scrape the precipitate right into a pile.
Scoop up the precipitate right into a ¼ teaspoon till it is as complete as possible. Ar the ¼ tespoon of precipitate into its labeled cup. Ar ¼ teaspoon of sodium bicarbonate and also calcium chloride right into their labeled cups.
Add 25 mL the water to every cup and also gently swirl till the solids dissolve as much as possible. Look to see the lot of hard that stays undissolved in every cup.

Expected results

The salt bicarbonate and also calcium chloride dissolve however the precipitate does not.

Since the precipitate does not dissolve prefer either of the reactants, it must be a different substance 보다 the reactants. Therefore, a chemical reaction must have actually occurred.


Do a demonstration to show students an additional example of a precipitate and also a shade change.

Tell students the you will present them an additional reaction that forms a precipitate and also a tiny something extra.

Materials for the Demonstration

Copper II sulfate household ammoniaHydrogen peroxide (3%)Water i graduated cylinderTest tube2 droppers1 clean plastic cup (empty)

Note: The copper compound is dubbed “copper II” because copper have the right to make different varieties of ions. It can lose one electron and be simply Cu+ or it have the right to lose two electrons and also be Cu 2+. This form of copper ion is called copper II. The “sulfate” in copper II sulfate is also an ion. This ion is comprised of an ext than one atom. It is just one of the polyatomic ions disputed in chapter 4, class 3. The sulfate ion is comprised of a sulfur atom external inspection to four oxygen atoms and also is treated as one ion (SO42−).

Teacher Preparation

Make a copper II sulfate systems by adding 5 g that copper II sulfate to 50 mL of water.


Pour 15–20 mL of copper II sulfate solution into a test pipe so it is about ½ full. Add about 10–20 fall of ammonia. Add around 10–20 autumn of hydrogen peroxide.

Expected outcomes

After including the ammonia, a whitish precipitate will form at the height of the copper II sulfate solution. As an ext ammonia is added, the color on optimal of the liquid will adjust to a deeper darker blue. As the hydrogen peroxide is added, the dark blue area at the top of the systems will rotate dark green and a dark precipitate will form.

Note: The details of the chemical reactions that create the different precipitates and also different color alters are fairly complicated. The key idea for students is the atoms or teams of atoms in the reaction rearranged and bonded in different ways to type different building material in the products.

Let students know that as soon as they check out the production of a gas, a precipitate, or a shade change, that this is evidence that a chemistry reaction has taken place.

Ask students:

How can you tell the something new was made as soon as the copper II sulfate and also ammonia reacted?A precipitate to be produced.How have the right to you tell that something brand-new was made once these substances reacted v hydrogen peroxide?The color readjust and other precipitate are proof of an additional chemical reaction.

In-Class or At-Home Project.

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Have students use objects such together gum drops, beads, M&Ms, Legos, or other small objects to stand for the atoms in 2 of the three reactions they have actually explored therefore far. Students can tape or adhesive the objects come poster board and also write under the chemistry formula for the reactants and products.