The Environment and Safety With Everything!
Miri Kesner, Science Teaching Department, The Weizmann Institute of Science
At a teacher’s workshop held at the Weizmann Institute of Science during the 1996-1997
academic year, the participants discussed inter alia two issues that are closely connected:
the environment and safety.
These issues are central and important in the chapters on the chemical industry, but they
can also be combined in the course of other chapters. The subjects of the environment
and safety can be employed to reinforce various concepts and subjects learned in the
chapters on energy, acids and bases, oxidation reduction and so on (see continuation),
and demonstrate their application by means of examples from both everyday life and the
chemical industry. These subjects are also of prime importance in school laboratory work
and in their practical application in everyday life.
Each chapter should be followed up with appropriate experiments that present the new
material learned in it, from the viewpoint that emphasizes its effects on the subjects of the
environment and safety. The gain here is in varying the teaching, combined with the
industrial and applicatory aspects of the chemistry syllabus and the inculcation of basic
concepts and principles regarding the environment and safety precautions at work.
We recommend dealing with this subject by first relating to the student’s close
environment and only later moving on to industry which is, of course, less familiar.
The following is a proposal for a discussion in class and also questions that may be raised
at each stage.
A.
What do we need to do in order to protect the environment and ensure safety
in the school laboratory?
Stage 1: Presentation of the problems
The teacher puts the following general question: What environmental and safety problems
arise during work in the school laboratory?
The following is an example of a list of problems that might arise in the laboratory:
How to store chemicals.
How to treat chemicals during experiments.
How to treat chemicals after the experiment.
What rules should be adopted to ensure safety at work?
What protective methods should be used?
How can we recognize the dangers?
Stage 2: Finding solutions to the problems
The central problem in a discussion in class is how to protect the environment and ensure
safety in the school laboratory.
A list of procedures or rules of conduct can be made up that can be classified according
to the different problems presented. Alternatively, either an official document from the
laboratory safety instructions or the school rules can be used, provided that the latter
relates to these subjects.
The following is an example of a list of procedures or rules of conduct that relates to
safety problems and protecting the environment:
 Food must not be brought into the laboratory and it is forbidden to taste or smell
substances in it.
 It is forbidden to touch substances and equipment without permission and the
appropriate knowledge.
 Wearing suitable clothing is compulsory: protective glasses, gloves, coveralls, etc.
 It is compulsory to store substances safely (examples: volatile substances must be
kept away from open flames, oxidizing substances must be kept away from reducing
substances, acids from bases, etc.)
 In the event of a mishap, the teacher or laboratory assistant must be called.
 It is compulsory to install faucets for eye washing and emergency showers in the
laboratory.
 Work with hazardous substances will only be done under a fume hood.
 Hazardous substances must not be poured down the sink.
 Different (non-hazardous) substances must not be poured down the sink together as
they are liable to react with one another and thus create high-risk situations, such as
overheating, explosion, and so forth.
 It is compulsory to take the appropriate steps for the collection and disposal of
substance waste; separate containers containing sand for the collection of different
types of solutions/liquids (examples: acids, bases, etc.) The full containers are then
taken to an authorized dump.
 It is compulsory to collect used batteries and dispose of them at an authorized
dump.
 Training: posters, clear guidelines for handling substances during experiments and
in the event of accidents, current training.
 It is compulsory to equip the laboratory with:
fire-fighting equipment: extinguishers, a sprinkler system, sand etc.
neutralizing agents: water, specific neutralizing solutions.
first-aid: equipment, procedures, appointment of a person responsible.
Stage 3: Examples of application
Work with press cuttings that discuss laboratory accidents. The students can be given
various cuttings and guiding questions, or one of them can be asked to present questions
connected with the cuttings and these can be answered in groups.
Questions like, “What do you do if a certain substance is spilt?” or calculation exercises
on the quantity of a substance required to neutralize a “dose” of another substance can
be presented.
B.
Can the problems presented in the laboratory be projected onto the
problems in an industrial plant?
The answer is, of course, affirmative, but the problems are on a much larger scale!
It is important to note that in both industry and the laboratory, the first stage is
familiarization with the risks (safety information sheets, data banks), and then to make an
assessment of the size of the risks and finally to take action to prevent and control
them.
C.
What must be done to protect the environment and ensure safety in
industry?
You can begin with an associative list (a full list or in the form of a sunburst chart) of
subjects relevant to industry, such as waste, sludge, emission of substances into the air,
water sources and the soil, safety, worker health hazards, and so on.
FACILITY DURABILITYUNDER
PRESSURE, ACIDS, TEMPRATURES ETC.
STORAGE RULES
WASTE DISPOSAL
EMERGENCY
PROCEDURES
PROTECTIVE AND
SAFETY EQUIPMENT
PROTECTING THE
ENVIRONMENT
AND ENSURING
SAFETY
EMERGENCY AND SAFETY
EQUIPMENT
SPOT CHECKS
PRODUCTION
INSTRUCTIONS
TRAINING AND
REFRESHER
COURSES
PERIODIC MEDICALS
In the discussion it is advisable to focus on the main considerations that must be taken
into account in protecting the environment and ensuring safety in industry (without going
into detail on specific methods).
The following are subjects that can be raised for discussion:
How to store.
How to manufacture.
How to handle products.
How to market.
How to dispose of waste.
How to deal with faults.
How to protect workers’ health.
The class can be divided into groups. Each group is given an article or a press clipping
relating to a different question and analyzes it in accordance with the guideline questions.
The use of data banks to obtain information on various substances may also be
recommended.
In cases in which accidents occurred, press cuttings should be used to show how they
were dealt with (both successfully and erroneously) and then the students should be
asked to suggest suitable and safe measures. The suggestions raised should be
compared and then judged by criteria like, what is safer? What is simpler? What costs
less? etc.
In conclusion, we recommend showing the safety information sheets (MSDS cards) of the
substances discussed. These cards contain details of the substances’ properties and
dangers and also the accepted treatment methods for them in the event of a leak or other
accident.
D.
Can the solutions presented in the laboratory be projected onto solutions in
an industrial plant?
Every solution presented with regard to work in the laboratory can be translated into
industrial terms, but in some senses industry has problems that do not exist in the
laboratory. The best example of this is cost, which is of decisive importance when dealing
with large amounts of materials and substances.
E.
Combining the subjects of the environment and safety with other subjects
studied.
The following are a number of examples of a combination of the subject with the various
other chapters:
Metals
 The processing of toxic metals and safeguarding the worker’s health. Examples: lead,
cadmium, mercury, beryllium, etc.
Ionic compounds
 Treatment of effluents containing metallic ions by means of precipitation reactions of
insoluble sulfides or hydroxides.
Acids and bases
 Storage of acids and bases.
 Handling acids and bases (H2SO4, HCl, NaOH, NH3).
 Handling acid and base residues (neutralizing agents).
In any event, the various possibilities of neutralization can be compared according to the
criteria derived from the substances’ properties and the type of process. For example:
substance volatility, toxicity, cost, process exothermicity, etc.
 Acid rain: the sources of acid rain and ways of preventing it.
Oxidation reduction
 Storage of oxidizing and reducing agents.
 Neutralization of oxidizing and reducing agents.
Energy
 Exothermic reactions and their dangers.
 The relationship between the amount of energy in a process and the amounts of the
substances in it.
 The effects of the state of matter of the substances on the enthalpy of the reaction.
Carbon Compounds
 Combustion processes and fire extinguishing methods.
 How do you handle volatile and flammable materials?
 What do you do with organic material waste?
F.
Proposals for laboratory experiments
All the experiments and demonstrations should be conducted while observing the
appropriate safety regulations!
You can begin with the reaction between solid sodium hydroxide and a solution of
hydrogen chloride in water. The students are usually familiar with this process from
previous chapters, however an experiment can be planned that emphasizes the subject of
safety precautions (for details of this experiment see in the article " Is a reaction between a
base and an acid likely to be dangerous" by Miri Kesner and Nurit Arad.
In this context, appropriate press cuttings can be found that deal with accidents illustrating
the possible dangers when handling familiar and apparently “innocent” substances the
wrong way.
After the completion of the experiment, questions like “Why did the accident occur?” or
“What should have been done to prevent it?” can be presented.
1.
A demonstration of the action of strong acids like H2SO4 and HCl on cloth, paper, metals
etc.
This experiment illustrates the damage that might be cause as a result of careless
use of substances like these.
2.
A demonstration of the actions of various neutralizing agents:
 Neutralizing an acid using an alkali (and vice versa), for instance:
H3O+(aq) + Cl-(aq) + Na+(aq) + OH-(aq)  2H2O(1) + Na+(aq) + Cl-(aq)
2H3O+(aq) + SO42-(aq) + Ca2+(aq) + 2OH-(aq)  4H2O(1) + CaSO4(s)
 Neutralizing an oxidizing agent by use of a reduction agent (and vice versa), for
instance:
3Br2(1) + 8NH3(g)  6NH4Br(s) + N2(g)
Br2(1) + 2S2O32-(aq)  2Br-(aq) + S4O62-(aq)
3Br2(1) + 3Ca(OH)2(s)  3Ca2+(aq) + 5Br-(aq) + BrO3-(aq) + 3H2O(1)
These alternative reactions can be discussed and compared with the neutralization of
bromine according to the state of matter of the neutralizing agents, the amount of energy
released, the results obtained, etc.
3.
(a)
The precipitation reactions of heavy metals such as Cu 2+, Fe3+ and Ni2+ as hydroxides or
sulfides, for instance:
Cu2+(aq) + 2Cl-(aq) + 2Na+(aq) + S2-(aq) 
CuS(s) + 2Na+(aq) + 2Cl-(aq)
Cu2+(aq) + 2Cl-(aq) + 2Na+(aq) + 2OH-(aq) 
Cu(OH)2(s) + 2Na+(aq) + 2Cl-(aq)
After demonstrating the actions of various neutralizing agents, a general discussion on
the following subjects is recommended:
Various risk factors, such as:
(b)
 The rise in temperature in exothermic reactions.
 Obtaining flammable gases.
 The rise in pressure resulting from gas emission.
 Corrosive materials.
The properties required of neutralizing agents:
 Do not react with an excessive exothermic reaction.
 Non-volatile.
 Non-flammable
 Gases are not produced during the reaction.
 Non-corrosive.
 Non-toxic.
 Relatively inexpensive.
In any event, the various possibilities of neutralizing a specific substance can be
compared according to criteria derived from the above-mentioned requirements, such as:
Which process is more exothermic? In which process are substances of greater
flammability, or which are more dangerous, produced? Which treatment method is the
most inexpensive? and so forth.
When analyzing the various methods of extinguishing fires, it is important to note that
adapting the means of fire fighting to the burning substances is mandatory. For example,
extinguishing the burning of magnesium alloys with CO2(g), H2O(1), or carbonates that
release CO2(g) during their decomposition is prohibited.
The introduction of appropriate enrichment articles and movies according to the level of
the students is recommended