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C2.10 · Plan and conduct a single-displacement inquiry

Learn to plan and conduct a single-displacement inquiry through clear examples and targeted practice.

Ontario Grade 11 Chemistry

Chemical Reactions

SCH3U study topic C2.10

A clean metal strip placed in a solution may become coated with a different solid. The solution may also change in appearance. These observations can be evidence that a chemical change has occurred. In this lesson, you will use a particle model and an activity series to plan an investigation of this kind. A plan is not the same as a completed experiment: observations must be recorded only after the investigation is actually carried out.

What you will learn

Describe the observable evidence that may indicate a single-displacement reaction.
Use an activity series to predict whether a metal will displace another metal from a compound.
Plan a fair, safe inquiry with a question, prediction, variables, procedure, and observations.
Represent a possible single-displacement reaction with a balanced chemical equation and state symbols.

1. From visible change to particle model

A single-displacement reaction is a reaction in which one element takes the place of another element in a compound. In this lesson, focus on a metal reacting with a compound that contains a different metal. For example, a metal strip placed in a solution containing dissolved metal ions may develop a coating. That coating can be a new solid metal.

A compound is made from two or more elements chemically joined. An ion is an atom or group of atoms with an electrical charge. In a solution of an ionic compound, some of its ions are separated and spread through the water. A particle-level model for a metal-displacement reaction is that atoms of the added metal become ions, while ions of the other metal become atoms. Those atoms may form a solid coating.

The visible coating is useful evidence, but one observation alone may not identify every product. Compare the strip and solution before and after the procedure, and record what you actually see. Do not write an expected result as though it were an observation.

A single-displacement reaction has an element and a compound as reactants.
A metal may replace a different metal in a compound if it is more reactive.
An observation is a record of what happened, not what you predicted.

2. Use the activity series to make a prediction

An activity series is a course reference list that ranks metals by their tendency to react. Use the Ontario SCH3U activity series supplied for your course. If the added metal is above the metal in the compound, the added metal can displace it. If it is below, the expected prediction is no single-displacement reaction.

For example, zinc is above copper in the usual course activity series. Zinc is therefore predicted to displace copper from copper(II) sulfate solution. The compound name tells you that its positive ion is copper(II), with a charge of

2+

. Sulfate has a charge of

2-

, so the formula unit is electrically neutral.

Write the product formulas using the ion charges and the course formula table. Zinc forms a

2+

ion, and sulfate remains a

2-

ion, so the dissolved product is zinc sulfate. Copper ions form copper metal. Check that the number of each kind of atom is the same on both sides. In this case, each is already present once on each side.

State symbols tell the reader the physical state of each substance: solid, aqueous (dissolved in water), liquid, or gas. They help describe the investigation conditions. The equation below represents the predicted reaction, not experimental evidence.

\mathrm{Zn(s) + CuSO_4(aq) \rightarrow ZnSO_4(aq) + Cu(s)}

Check the activity series before writing a prediction.
Use ion charges to write correct formulas; do not change subscripts to balance an equation.
A balanced equation has the same number of each type of atom on both sides.

3. Plan a fair and safe inquiry

A useful inquiry question is focused and testable. For example: “Does a zinc strip displace copper from copper(II) sulfate solution?” A prediction answers the question before testing and gives a reason. Here, the activity series supports predicting that a copper-coloured solid may form on the zinc. This is a prediction only; it is not a recorded result.

A fair test changes one factor while keeping other important conditions the same. The independent variable is the factor you choose to change. The dependent variable is the evidence you observe or record. Controlled variables are conditions you keep the same. For a comparison of two metal strips in the same solution, the independent variable could be the metal-strip identity. The dependent variable could be whether a visible coating forms. Keep the solution volume and concentration, the strip size, and the observation time the same.

Plan the procedure before starting. Label the containers clearly. Measure the same volume of solution into each container and use strips with comparable exposed surface areas. Clean and handle strips as directed by the teacher. Place each strip in its assigned solution, start timing in the same way, and record the initial appearance. At the chosen observation times, record changes to the strip and solution using words or a labelled sketch. Include a comparison that can show whether a change occurs without the proposed reacting metal, as directed by the teacher.

Safety is part of the plan. Follow the teacher’s instructions and the safety information for the chemicals. Wear required eye protection and other protective equipment. Avoid skin or eye contact, do not taste chemicals, and wash hands after the activity. Use only the quantities and disposal method approved by the teacher. Do not pour solutions into a drain unless instructed.

After carrying out the procedure, organize observations in a table. Keep observations separate from interpretations. For instance, “a reddish-brown coating appeared” is an observation; “copper formed” is an interpretation supported by the prediction and other evidence. If there is no visible change, record that accurately rather than changing the result to fit the prediction.

State the question, prediction, variables, procedure, and safety steps before beginning.
Keep conditions consistent when comparing trials.
Record actual observations and distinguish them from explanations.

4. Conduct, record, and interpret

During the investigation, follow the planned steps and note any necessary change to the procedure. Record the change and the reason for it. Do not treat an unplanned change as though the original conditions were maintained.

When interpreting results, compare the evidence with the prediction. A new solid on the added metal is consistent with displacement, but explain the result using the activity series and the particle model. In the zinc and copper(II) sulfate example, the model predicts that zinc atoms become zinc ions and copper ions become copper atoms. The equation summarizes this predicted change.

A useful conclusion answers the inquiry question and refers to the recorded evidence. If the results do not match the prediction, report that honestly. Check whether the procedure was followed and whether observations were clear. A conclusion should not claim more than the evidence supports.

Chemical equations do not include measured quantities unless the inquiry measures them. For this expectation, focus on planning the comparison, observing evidence, and using a balanced equation to represent the possible reaction. If you record a measurement, include its unit and the precision provided by the measuring tool.

Use the results you recorded, even when they differ from the prediction.
Connect evidence to the activity series and particle model.
Keep the conclusion limited to what the inquiry supports.

Worked example

Plan an inquiry using zinc and copper(II) sulfate

A class wants to investigate whether zinc displaces copper from copper(II) sulfate solution. Develop a prediction, identify the variables, and state what should be recorded. Do not report imagined observations.

Check the reaction prediction
Consult the course activity series. Zinc is above copper, so predict that zinc can displace copper from the solution. The prediction is not a result; the class must carry out the procedure to obtain evidence.
Write the symbolic representation
Use the formulas for zinc, copper(II) sulfate, zinc sulfate, and copper. Include states for the planned conditions. Count each type of atom to confirm that the equation is balanced.
$\mathrm{Zn(s) + CuSO_4(aq) \rightarrow ZnSO_4(aq) + Cu(s)}$
Choose variables and observations
For a comparison, change the identity of the metal strip and keep the solution volume, concentration, strip size, and observation time consistent. Record the initial and later appearance of each strip and solution. Note whether a coating appears, but do not identify it as copper until interpreting the evidence.
Complete the inquiry plan
Write the question, prediction, procedure, and safety steps before starting. Use teacher-approved equipment and disposal instructions. After conducting the inquiry, use only the recorded observations to decide whether the evidence supports the prediction.

Answer: The prediction is that zinc can displace copper. The balanced equation represents that possible reaction. The inquiry should compare a chosen metal strip under consistent conditions and record actual changes to the strip and solution.

Check: The equation has one zinc atom, one copper atom, one sulfur atom, and four oxygen atoms on each side. Both sides are neutral overall.

Common mistakes and how to avoid them

Predicting displacement because two substances are mixed.

Correction: Check the activity series. The added metal must be above the metal it is predicted to replace.

Changing a formula subscript to balance an equation.

Correction: Keep each chemical formula intact. Balance by changing coefficients only when needed.

Writing the predicted coating as an observed result before the experiment.

Correction: Label it as a prediction. Record observations only after carrying out the procedure.

Changing several conditions at once in a comparison.

Correction: Change the chosen independent variable and keep other important conditions consistent.

Lesson summary

A single-displacement reaction occurs when one element replaces another element in a compound.
Use the activity series to decide whether a metal is predicted to displace another metal.
Plan a focused question, prediction, variables, procedure, and safety steps.
Record observations honestly, then interpret them using the particle model and a balanced equation.

Check your understanding

Question 1

In the usual course activity series, zinc is above copper. What is the prediction when zinc is placed in copper(II) sulfate solution?

Zinc is predicted to displace copper.
Copper is predicted to displace zinc.
The activity series predicts no displacement.
correctIndex

Show answer and explanation

Zinc is predicted to displace copper.

The metal higher in the activity series can displace the metal lower in the series from its compound.

Question 2

Which statement is an observation rather than an interpretation?

A reddish-brown coating appeared on the strip.
Copper ions changed into copper atoms.
The reaction proves the activity series is always correct.
correctIndex

Show answer and explanation

A reddish-brown coating appeared on the strip.

The first statement describes something directly seen. The second explains a particle-level change, and the third makes a broad claim.

Question 3

For a fair comparison of two metal strips in the same solution, which plan is best?

Use different solution volumes and different observation times.
Change the strip identity while keeping key conditions consistent.
Change the strip identity, solution concentration, and strip size together.
correctIndex

Show answer and explanation

Change the strip identity while keeping key conditions consistent.

Keeping important conditions consistent helps make the strip identity the factor being compared.

Key terms

Single-displacement reaction: A reaction in which one element takes the place of another element in a compound.
Activity series: A course reference list that ranks metals by their tendency to react.
Ion: An atom or group of atoms with an electrical charge.
Independent variable: The factor deliberately changed in an inquiry.
Dependent variable: The evidence or outcome observed or recorded in response to a change.
Controlled variable: A condition kept the same to support a fair comparison.

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About this lesson and its review

Published by DoAssignment. This AI-assisted lesson follows Ontario Grade 11 Chemistry (SCH3U), expectation C2.10. It is a study resource, not an official curriculum publication.

Before publication, the draft is checked for structure, mathematical or chemical notation, calculations, course boundaries, and readability, and then requires administrator approval. Errors can still occur, so corrections are welcomed.

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