Key Concepts

The ions or molecule in two solutions have the right to react to kind a solid.A solid formed from two solutions is called a precipitate.

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


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


Download the student activity sheet, and distribute one every student as soon as specified in the activity. The activity sheet will certainly serve together the “Evaluate” ingredient of every 5-E great plan.


Copper II sulfate is available from various chemical suppliers, including Sargent Welch, Product #WLC94770-06 or Flinn Scientific, Product #C0110. Follow all safety and security precautions about use, storage, and disposal of copper II sulfate and also sodium carbonate. Sodium carbonate is Product #WLC94291-06 or #S0052.

Materials because that the Demonstrations

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

Materials for Each Group

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

About the Materials

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


Do a demonstration by combining 2 clear colorless options that develop a white solid and introduce the term precipitate.

Materials because that the Demonstration

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

Teacher Preparation

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



Have students incorporate two liquids come observe another precipitate.

Question to Investigate

How execute you know when a precipitate is developed in a chemistry reaction?

Materials because that Each Group

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

Note: If you would favor students to exercise using a balance to sweet grams, have them weigh two grams every of baking soda and also calcium chloride.


Use masking tape and a pen to label 2 plastic cup baking soda solution and calcium chloride solution. Usage a graduated cylinder to include 20 mL that water to each cup. Add 2 g (about ½ teaspoon) of calcium chloride come the water in its labeled cup. Swirl until as much of the calcium chloride dissolves as possible. Add 2 g (about ½ teaspoon) that baking soda come the water in its labeled cup. Swirl till as lot of the baking soda dissolves together possible. There might be part undissolved baking soda continuing to be in the bottom of the cup.

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


Expected Results

Bubbling and also a white precipitate appear.

Discuss college student observations.

Ask students:

What did you observe once you blended the baking soda solution and also the calcium chloride solution?The solutions bubbled and tiny white corpuscle of hard formed. Go you observe a precipitate? Yes. The white particles appeared after the two remedies were combined.Do you think this to be a chemistry reaction? Yes. Why?The 2 substances the were merged were liquids and also the substances the were produced were a solid and a gas. These products seem to be different from the reactants.Explore

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

Ask students:

How carry out you think we can separate the precipitate from the various other products?

Question come Investigate

Can you different the calcium carbonate from the rest of the products?

Materials because that Each Group

Coffee filter or document towelTall clean plastic cup


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

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

Allow the fluid to drip with the filter. This may take a while. Collection the precipitate next and allow the water to evaporate.

Expected results

A white hard will continue to be in the coffee filter. After ~ the water evaporates, the calcium carbonate will certainly be a white powder.

Note: If you’d like to different the sodium chloride native the water that flowed through the filter, to water the liquid right into a clean north cup and permit the water come evaporate because that a few days. As the water evaporates, college student will begin to watch cubic-shaped salt crystals developing in the solution. Eventually only salt crystals will remain in the cup.

Ask students:

What is the heavy white problem on the paper?Calcium lead carbonate (chalk).Is filtering the end the calcium carbonate and allowing the water to evaporate a chemical readjust or a physical change? physical change. Why? these substances were currently present in the water, therefore no new chemicals are made. What evidence was there the a chemical reaction arisen when you combined baking soda solution and calcium chloride solution? A gas and also a white solid were formed

Confirm the a chemistry reaction took place

Ask students:

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

Question to Investigate

Is the solubility that the precipitate different than the solubility of 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 the water?Yes

Materials because that Each Group

Dry precipitate on record towelBalance3 little plastic cupsGraduated cylinderGraduated cylinderPopsicle rod (optional)Calcium chlorideBaking sodaWater


Label 3 cup sodium bicarbonate, calcium chloride, and precipitateUse a spoon or popsicle stick come scrape the precipitate into a pile.
Scoop increase the precipitate into a ¼ teaspoon till it is as complete as possible. Ar the ¼ teaspoon of precipitate into its labeled cup. Ar ¼ tespoon of salt bicarbonate and calcium chloride into their labeled cups.
Add 25 mL that water to each cup and gently swirl until the solids dissolve as much as possible. Watch to view the amount of hard that stays undissolved in each cup.

Expected results

The sodium bicarbonate and also calcium chloride dissolve but the precipitate go not.

Since the precipitate does not dissolve like either that the reactants, it must be a various substance than the reactants. Therefore, a chemistry reaction must have occurred.


Do a demonstration to show students another example that a precipitate and also a color change.

Tell students that you will display them one more reaction that forms a precipitate and a small something extra.

Materials for the Demonstration

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

Note: The copper compound is called “copper II” since copper have the right to make different varieties of ions. It have the right to lose one electron and be simply Cu+ or it have the right to lose 2 electrons and also be Cu 2+. This form of copper ion is referred to as copper II. The “sulfate” in copper II sulfate is also an ion. This ion is comprised of an ext than one atom. It is one of the polyatomic ions questioned in thing 4, great 3. The sulfate ion is comprised of a sulfur atom bonded to four oxygen atoms and is treated together one ion (SO42−).

Teacher Preparation

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


Pour 15–20 mL the copper II sulfate solution right into a test tube so that is about ½ full. Add around 10–20 drops of ammonia. Add around 10–20 drops of hydrogen peroxide.

Expected results

After adding the ammonia, a whitish precipitate will form at the optimal of the copper II sulfate solution. As more ammonia is added, the color on top of the liquid will adjust to a depths darker blue. Together the hydrogen peroxide is added, the dark blue area at the top of the systems will turn dark green and also a dark precipitate will certainly form.

Note: The details of the chemical reactions that develop the various precipitates and also different color changes are fairly complicated. The key idea because that students is that atoms or teams of atom in the reaction rearranged and bonded in different ways to type different substances in the products.

Let students understand that once they check out the manufacturing of a gas, a precipitate, or a shade change, the this is proof that a chemistry reaction has actually taken place.

Ask students:

How can you tell the something new was made when the copper II sulfate and ammonia reacted?A precipitate to be produced.How deserve to you tell that something brand-new was made when these building materials reacted through hydrogen peroxide?The color adjust 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 tiny objects to represent the atoms in 2 of the 3 reactions they have actually explored so far. Students have the right to tape or glue the objects come poster board and write under the chemistry formula for the reactants and also products.