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C1.1 · Analyse industrial reactions that affect community health and safety

Learn to analyse industrial reactions that affect community health and safety through clear examples and targeted practice.

Ontario Grade 11 Chemistry

Chemical Reactions

Reading a reaction as both a chemical change and a community concern

A community near an industrial site may notice a strong odour, a visible plume, or dust settling on surfaces. These observations can raise questions about health and safety. Chemistry helps us identify substances involved and describe how they form. An equation alone cannot tell us how much of a substance is released or whether a particular person has been exposed. A careful analysis combines the reaction model with information about the substance, the release, and the people who could be affected.

What you will learn

Identify the reactants and products in an industrial reaction.
Use a balanced chemical equation to describe what is produced.
Connect an industrial product or emission to possible effects on community health and safety.
Distinguish what an equation shows from what it does not show.

1. Bridge from chemical equations to community questions

A chemical reaction changes starting substances into new substances. The starting substances are called reactants. The new substances are called products. In a chemical equation, reactants appear on the left and products appear on the right.

A balanced equation has the same number of each kind of atom on both sides. This reflects that atoms are rearranged rather than created or destroyed in the reaction. Coefficients are numbers placed in front of formulas to balance an equation. They do not change the substances’ formulas.

Industrial reactions take place as part of making or processing materials. To analyse one for community health and safety, first identify its products. Then ask whether a product can leave the process, how people or the environment could encounter it, and what information is still needed to judge the concern.

\text{reactants} \rightarrow \text{products}

Reactants are starting substances; products are substances formed.
Balance equations by changing coefficients, not subscripts.
An industrial process can make useful products and also create substances that need careful handling.

2. From an observable release to a particle model

Consider a metal-processing plant that heats a sulfide ore in air. A plume or an odour downwind could prompt questions about air emissions. The observation is a reason to investigate; it is not, by itself, proof of which substance is present or of a health effect.

At the particle level, the atoms in the ore and oxygen are rearranged. In the example below, zinc sulfide and oxygen form zinc oxide and sulfur dioxide. Sulfur dioxide is a gas. If it escapes into the air, people may breathe it. Exposure to sulfur dioxide can irritate the respiratory system, so a release can matter for community health, especially for people with breathing conditions.

The chemical equation identifies substances and shows their relative particle counts. It does not show the amount released, the concentration in air, wind direction, exposure time, or the health outcome for a specific person. These require other evidence, such as reliable monitoring and information about the release and location.

2\mathrm{ZnS(s)} + 3\mathrm{O_2(g)} \rightarrow 2\mathrm{ZnO(s)} + 2\mathrm{SO_2(g)}

A visible plume or odour can signal a question, but does not identify a chemical on its own.
Sulfur dioxide is a product in the example and a possible inhalation concern if it is released.
A chemical equation describes a reaction, not the size or severity of a community exposure.

3. Building a balanced equation and interpreting it

Read each formula carefully. The reactants are solid zinc sulfide and oxygen gas. The products are solid zinc oxide and sulfur dioxide gas. State symbols give the physical state: (s) means solid and (g) means gas.

To balance the equation, count each kind of atom on both sides. Zinc sulfide contains one zinc atom and one sulfur atom. Zinc oxide contains one zinc atom and one oxygen atom. Sulfur dioxide contains one sulfur atom and two oxygen atoms. Choosing coefficients of two for zinc sulfide, zinc oxide, and sulfur dioxide gives two zinc atoms and two sulfur atoms on each side. Three oxygen molecules provide six oxygen atoms, matching the two in zinc oxide plus four in sulfur dioxide.

The balanced equation says that two formula units of zinc sulfide react with three molecules of oxygen to form two formula units of zinc oxide and two molecules of sulfur dioxide. This is a ratio in the reaction model. Without a stated sample amount, it does not give a mass released or a concentration in air.

\mathrm{Zn}: 2=2,\quad \mathrm{S}: 2=2,\quad \mathrm{O}: 6=6

Count atoms of each element on both sides.
Coefficients balance atom counts; subscripts describe the substances and must stay unchanged.
The equation gives a particle ratio, not an exposure measurement.

4. A clear framework for industrial analysis

A useful analysis links the reaction to people and place. Start with the industrial activity and the observable concern. Identify the reactants and products from a reliable description of the process. Use a balanced equation, when the reaction is known, to make the chemical change clear.

Next, identify a possible route of contact. A gas released to outdoor air may be inhaled; a liquid spill could contact skin or enter water. Do not assume a route without evidence. Consider who may be nearby and whether some people could be more affected. Keep the wording proportional: say that a substance can pose a concern under exposure, rather than claiming harm occurred without supporting evidence.

Finally, name the limits of the information. A balanced reaction cannot establish how much escaped or whether safety limits were exceeded. Those questions depend on measurements and reliable local information. This distinction helps avoid both dismissing a real concern and making claims that the evidence does not support.

Connect process, product, possible release, route of contact, and people who may be affected.
Separate observed evidence from conclusions and unanswered questions.
Use measurements and reliable information to evaluate the extent of a release.

Worked example

Analysing a possible sulfur dioxide release

A metal-processing facility uses air while heating zinc sulfide ore. A nearby resident reports an unusual odour. Use the reaction model to explain what chemistry may be relevant, what health and safety concern could arise, and what the equation cannot establish.

Identify the reaction
The described process can be represented by the balanced reaction of zinc sulfide with oxygen. The products are zinc oxide and sulfur dioxide. The gas product is relevant to an air-release question.
$2\mathrm{ZnS(s)} + 3\mathrm{O_2(g)} \rightarrow 2\mathrm{ZnO(s)} + 2\mathrm{SO_2(g)}$
Connect product and possible contact
If sulfur dioxide escapes from the process, people nearby could breathe it. Because inhaled sulfur dioxide can irritate the respiratory system, a release could be a community health concern. The odour report alone does not prove that sulfur dioxide caused it.
State what more is needed
The equation gives the substances and their relative amounts in the reaction, but it does not state whether a release occurred or how large it was. Reliable air measurements and information about the time and location of any release would be needed to assess exposure.

Answer: The reaction can produce sulfur dioxide gas, which could pose an inhalation concern if released. The odour report is a reason to investigate, not proof of the gas’s identity or of exposure.

Check: The equation conserves two zinc atoms, two sulfur atoms, and six oxygen atoms on each side. It contains no measurement of air concentration or release amount.

Common mistakes and how to avoid them

Changing a subscript to balance an equation.

Correction: Change coefficients only. A subscript change would describe a different substance.

Treating an odour or visible plume as proof of a particular chemical.

Correction: Treat the observation as a reason to investigate. Chemical identification needs suitable evidence.

Using a balanced equation to claim that a community was exposed to a harmful amount.

Correction: An equation shows the reaction and particle ratio. Exposure claims require information about release and contact.

Lesson summary

Industrial reactions form products that may have health and safety importance if released.
A balanced equation shows the substances and conserves atoms.
Analyse a community concern by linking the process, product, possible release, route of contact, and people affected.
Keep conclusions within the evidence. An equation does not measure exposure.

Check your understanding

Question 1

In the zinc sulfide reaction, which product is a gas that could be relevant to an air-release concern?

Zinc sulfide
Oxygen
Zinc oxide
Sulfur dioxide

Show answer and explanation

Sulfur dioxide

Sulfur dioxide is shown as a gas product. Its presence in the equation does not prove that it was released from a facility.

Question 2

What does balancing a chemical equation establish?

The same number of each kind of atom appears on both sides.
The exact amount of gas released to the community.
That an odour came from a specific product.
That every nearby person was exposed.

Show answer and explanation

The same number of each kind of atom appears on both sides.

Balancing conserves the count of each kind of atom. Release amounts, chemical identification in air, and personal exposure require other evidence.

Question 3

A resident reports an unusual odour near an industrial site. Which conclusion is best supported by that observation alone?

A harmful concentration has been measured.
Sulfur dioxide caused the odour.
The report gives a reason to investigate, but does not identify the substance.
No release could have occurred.

Show answer and explanation

The report gives a reason to investigate, but does not identify the substance.

An odour report is an observation, not a chemical identification or concentration measurement.

Key terms

Reactant: A starting substance in a chemical reaction.
Product: A substance formed in a chemical reaction.
Coefficient: A number placed in front of a chemical formula to balance an equation.
Exposure: Contact between a person and a substance, such as breathing a gas.
State symbol: A symbol in an equation that shows a substance’s physical state, such as (s) for solid or (g) for gas.

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About this lesson and its review

Published by DoAssignment. This AI-assisted lesson follows Ontario Grade 11 Chemistry (SCH3U), expectation C1.1. 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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