Worksheet for Video #1 - Testing Gases: H2, O2, and CO2
Complete this page after viewing the video and performing the investigation.
1. What is the flame source shown in the video? What other flame source is readily
available in a typical high school lab? What are the advantages and disadvantages of each
source?
A BBQ lighter ignites a candle.
Bunsen burners are readily available in school labs.
Candle: advantages - more accessible for all students; its flame is more easily seen;
disadvantages – easily knocked over in a school lab during a student investigation;
students may need to relight this flame source; drips hot wax.
Bunsen Burner: advantages – does not drip hot wax; usually stays lit until turned off;
disadvantages - not easily accessible for all students; flame may not be easily seen; loose
clothing can easily ignite; build up of gas in lab can occur during student investigation if
students not skilled in lighting Bunsen burner.
2. Consider the following scenario. A class of 25 students use a single candle located at the
teacher’s bench to ignite their wooden splints and return to their work area. What fire
hazard does his scenario pose? How can the risk be minimized?
Students would be required to light the wooden splint at the front of the room and carry
the splint through the room to the workstation. The risk can be minimized by providing
the groups of students with their own candle and the teacher lighting the candles for each
group.
3. What are the fire hazards in this investigation?
Students are working with an open flame, so any material near the flame can ignite. Also,
students may need to relight the flame source, creating more opportunity for an
unexpected event. Keeping the work area clear of clutter is therefore essential to
minimize the risk of accidental combustion.
Calcium metal is highly reactive and only the quantity of calcium required for the
investigation should be brought into the classroom. As hydrogen is explosive, give
student groups small amounts of calcium for their reaction to ensure only small amounts
of the gas are produced.
4. Why is a dry scoopula preferred over paper when transferring calcium?
Calcium reacts vigorously with water, so a dry piece of equipment is necessary. Paper
may not be dry enough for a safe transfer.
5. How can the risk for this activity be reduced?
Although a demonstration of the procedure is a good idea, students are expected to
conduct these tests. Be aware of the student skill level and consider organizing this lab
into stations. Students can move from less risky activities (such as viewing a streaming
video or brainstorming some ideas) to a station with close teacher supervision and small
amounts of chemicals. Each gas test can be conducted on separate days so that there are
fewer materials, less clutter and physical motion and less risk.
6. The video shows the use of a spark lighter or BBQ lighter rather than matches. How do
matches create more risk?
Matches are made of paper or wood and can combust unexpectedly. The spark lighter
only provides a spark; a flame is produced when the fuel is present. A BBQ lighter does
contain fuel and the sparker, but it is safer for lighting a candle.
7. The test tube collecting the gas generated by the calcium metal is only partially filled by
the generated gas.
a) Why is this important to the success of the investigation?
The flame test for hydrogen gas requires that hydrogen combust with oxygen. Leaving
some water in the test tube allows oxygen from the environment to move into the test
tube for the characteristic ‘pop’.
b) How does collecting more gas create more risk?
Excess hydrogen gas in the absence of oxygen will not combust. This creates a situation
where students are unsure of what to do next while they are holding an open flame on
the wooden splint. During this time the splint may burn down to their fingers causing a
mild burn or cause students to drop the wooden splint and create a fire hazard on the
desk or bench surface.
8. What are possible alternatives to manganese (IV) dioxide, MnO2, when generating
oxygen gas?
Raw potatoes are an excellent source of the enzyme catalase, which also catalyses this
decomposition reaction. Prepare potato juice just before using it, because it does denature
quickly.
Worksheet for Video #2 - Reactivity of Metals: Li, Na, and K
Complete this page after viewing the video and performing the investigation.
1. What is the educational purpose of demonstrating the reactivity of the alkali metals?
The reactivity of the alkali metals increases as you descend the group I elements of the
periodic table.
2. Why is it necessary to keep the quantity of alkali metal in the classroom to a minimum?
Alkali metals are light, flammable metals that react vigorously with water to produce
hydrogen gas. A pea-size sample is appropriate for a teacher demonstration but too large
for a student investigation. Do not be tempted to use larger pieces of these metals to
produce larger and more dramatic flames. The reaction, particularly with potassium may
become too unpredictable.
3. Why is it essential for all equipment that comes in contact with the alkali metal samples
to be coated with mineral oil?
Alkali metals react vigorously with water so it is important to ensure that they do not
come into contact with possible sources of water. Cut each metal sample on a tray with
oil to prevent accidental contact with water.
4. Why is lithium safer for students to use than potassium?
Lithium reacts less vigorously with water than either sodium or potassium to produce less
heat energy, so the risk of creating a hydrogen gas explosion is greatly reduced.
5. Why is a safety shield required for the demonstration?
Sodium and potassium react vigorously with water to create a lot of heat energy. As a
result, the risk of hydrogen gas exploding is greater. This means that a small piece of
metal can be raised out of the water from the explosion. Moving as a projectile, these
pieces of metal can land on a person or object and continue to react. Very rarely, glass
can break and the shield offers protection from broken glass.
6. Why is phenolphthalein added to the water?
Phenolphthalein indicator provides a visible trail of the moving metal. In the Grade 11
Chemistry University course this pink trail is also evidence of the formation of a base as a
product of the reaction.
7. How will the activity change if phenolphthalein is not added?
The alkali metal reaction with water will not change, but the trail showing the movement
of the metal will not be visible. As a demonstration, this means that some students may
have more difficulty observing the action of the metal in the water.
8. Why is a wide-mouth container like a beaker preferable to a narrow-mouth container like
an Erlenmeyer flask or test tube for this investigation?
Open beakers allow the hydrogen gas to dissipate more easily. More constrained
containers will concentrate the gas and the heat of reaction is then more likely to cause
the hydrogen gas to combust and possibly lead to a fire or an explosion.
9. Why is a wire mesh placed above the beaker in which the alkali metal reacts with water?
A square wire mesh is placed over the mouth of the beaker to prevent the alkali metals
from being ejected from the beaker.
10. Explain why leftover pieces of metal must NOT be discarded in the trash or the sink.
These metals are flammable materials. They will react with water to release energy that
can lead to a fire or an explosion.
11. What are possible fire hazards when working with the alkali metals?
Alkali metals react vigorously with water to create hydrogen gas. The heat of reaction
with sodium and potassium is high enough to ignite the gas and cause an explosion. A
small explosion can push the metal out of the container so that it can land on a person or
combustible material and continue to react. Keep all samples of the alkali metals in
mineral oil until they are to be used to avoid accidental contact with water.
12. Observation charts can be developed by students or created by teachers. How does each
method reflect different student skill levels for this investigation?
Observation charts created by students require them to understand what they are going to
observe and record. Teacher observation charts help students focus on specific aspects of
the inquiry to build both their observation skills and recording skills. Students should be
exposed to both situations as they reflect different levels of experience and skill
development.
Worksheet for Video #3 - Oxidation of an Alcohol using a Catalyst
Complete this page after viewing the video and performing the investigation.
1.
Why was the stopper removed when the test tube of methanol was placed in the water
bath?
The thermal energy of the water bath readily vaporizes methanol. This would result in
an increase of gas pressure if the test tube was sealed. This increase in pressure could
eject the stopper or break the test tube.
2.
Why was the platinum heated at a safe distance away from the water bath?
Methanol is a very flammable liquid. Consequently, the platinum strip should be heated
a few metres away from the methanol to avoid accidental ignition of methanol vapour.
3.
What are the reactants and products of this reaction when the platinum glows bright
red?
The reactants are methanol and oxygen. The products are carbon dioxide and water and
represent the complete combustion of methanol.
4.
What other product is possible if the oxygen supply is limited? Why should this reaction
be only conducted in a well-ventilated area like in a fume hood?
When the oxygen supply is limited, methanal (formaldehyde) may also be produced.
Since formaldehyde is toxic, the demonstration should only be conducted in a wellventilated area to limit the inhalation of formaldehyde vapours.
5.
What is the role of platinum in this reaction?
Platinum is a catalyst in this reaction and without platinum the reaction is too slow.
When oxygen is not limiting the energy released by the complete combustion of
methanol causes the platinum to glow red. When oxygen is limiting, incomplete
combustion occurs, and the energy released will not cause platinum to heat to red hot.
6.
Methanol is one of the most volatile organic solvents found in a typical high school
laboratory. Why is the high volatility of methanol a fire safety hazard? How can this
risk be minimized?
Since methanol is so volatile, it quickly evaporates into a highly flammable vapour. The
fire hazard of methanol vapour can be minimized by ensuring the methanol stock bottle
is not brought into the lab, keeping the quantities of methanol used to a minimum and
conducting the demonstration in a well ventilated area away from open flames or
devices that could generate an electric spark or discharge.
Worksheet for Video #4 - Acetylene Production from Calcium Carbide
Complete this page after viewing the video and performing the investigation.
1. What personal safety precautions are necessary prior to conducting an investigation that
involves open flames?
Personal safety precautions should include: safety goggles; insulated gloves for handling
hot glass; ensuring that long hair is tied back, hats removed, and loose clothing and
jewelry is tucked in or removed; extinguishing the source of flame as soon as it is no
longer required; a bucket of sand available to extinguish unexpected flame.
2. Why is it recommended not to bring the stock bottle of a reactive chemical like calcium
carbide into the classroom?
Calcium carbide reacts readily with water to produce flammable acetylene gas.
Minimizing the quantity of calcium carbide in the classroom and keeping it in sealed
vials reduces the risk of accidental water spills reacting with calcium carbide. It also
prevents mischievous students from taking some calcium carbide for unauthorized use.
3. What are some advantages of organizing this investigation using stations around the
room?
Organizing the investigation in stations minimizes the movement of students in the
classroom. This saves time and reduces the risk of spills and accidental falls.
The use of a fixed number of stations also facilitates the control of the amount of
materials and equipment in use during the investigation.
4. Why should the size and quantity of calcium carbide pellets made available at each
station be strictly controlled?
Controlling the quantity of calcium carbide available minimizes the quantity of
flammable acetylene gas generated and helps ensure it is not used for unauthorized
purposes.
5. Why should this investigation only be conducted in a well-ventilated room?
Proper ventilation ensures that excess acetylene gas does not build up in the classroom.
Students should be cautioned to place their reaction mixture in the fume hood if it
generates more acetylene gas than is required.
6. In a related investigation, burning a mixture of 10% acetylene and 90% air produces a
loud and startling popping sound. What precautions do you recommend to maintain
safety and avoid breakage during this investigation?
Warn students to expect a loud pop when burning dilute acetylene mixtures. Instruct
them to hold the test tube securely as they conduct the investigation.
7. What precautions should be taken when storing stock containers of water reactive
chemicals like calcium carbide?
Calcium carbide should be stored in its stock bottle in a water proof container in the stock
room far away from sinks or overhead pipes. It should be stored away from oxidizers,
corrosive liquids, and flammable solids. The label should indicate that it reacts with water
to form flammable substances.
Worksheet for Video #5 - Safely Synthesizing Esters
Complete this page after viewing the video and performing the investigation.
1. Since most organic compounds are combustible, the risk of unintentional combustion is
always present when using these compounds. What are two possible energy sources that
could ignite a volatile organic substance?
Open flames and heat sources.
How can the risk of these sources be minimized?
A water bath is the preferred heat source when warming any flammable liquid. Heat
sources with open flames should not be used because the flame could ignite the
combustible vapour. To prevent the buildup of excess vapours during investigations
involving the heating of organic compounds the water bath should be kept several
degrees below the boiling point of the compound and the lab well ventilated.
2. Identify two pieces of safety equipment that could be used to put out an unintentional fire
in this investigation.
Fire extinguisher and sand bucket.
3. How can the risk involved with handling concentrated acids be minimized?
Stock bottles of concentrated acids should never be brought into the classroom. All
decanting, dilution and/or preparation of concentrated acids should be done in the prep
room fume hood. Small quantities of chemicals should be used so that the volume of
concentrated sulfuric acid required can be kept to a minimum. The teacher should review
the appropriate handling procedures for concentrated acids with students prior to the
investigation and plan to dispense the concentrated acid.
4. (a) What guideline(s) should be used when selecting the temperature of the water bath
used in this investigation?
Methanol is a flammable and volatile liquid. To prevent the build up of excess vapours
during ester synthesis the water bath should be kept several degrees below the boiling
point of the alcohol (boiling point of methanol is 64.7°C) being used.
(b) What document could you consult to find this information?
The MSDS for each reactant and product should be referenced during the planning stages
of the investigation and assessed for safety during use.
5. Why is clamping the test tube containing the ester synthesis mixture in the water bath not
recommended?
A test tube holder is used instead of clamping the test tube in place so that the reactants
can be quickly removed from the water bath if there are any signs of boiling. Also, the
use of a test tube holder provides more flexibility in holding the test tube in the water
bath while ensuring it is pointed away from all other persons in the lab.
6. What is the proper technique of smelling a gas in an investigation?
In scientific investigations the proper way of smelling a gas is to use the technique of
wafting to avoid inhaling the gas. (See page 31 in Safe ON Science for further details).
7. How would you manage the distribution of materials to your students during the ester
synthesis activity to promote safety?
Dropper bottles prepared for each group ensure that no student has large quantities of any
particular reagent.
Have sign in and sign out sheet for equipment
Make only small graduated cylinders or 1 mL pipettes available to your students to
discourage the dispensing of more reactants than is called for in the procedure.
Teachers should plan to dispense the concentrated sulfuric acid catalyst.
8. What are the three important safety considerations that you would discuss with your
students prior to conducting this investigation?
Do not bring lighters or matches into the classroom during this activity as there will be
more volatile fumes than usual in the air
Watch your reaction carefully while it is in the water bath and pull out the test tube at the
first sign of boiling
Do not exceed the recommended temperature of the water bath (review of pertinent
information from MSDS sheets with students)
9. What would you do if one of the student reaction mixtures ignited?
If the vapours in the test tube were to ignite the easiest solution may be to dump the
contents of the test tube into the water bath, diluting the reagents and quenching the
flame. In the case of a larger fire dumping the bucket of sand onto the surface is likely the
next best step. The fire extinguisher can be used for larger fires or those that are not on
flat, horizontal surfaces.
Worksheet for Video #6 - Aseptically Preparing a Bacterial Streak Plate
Complete this page after viewing the video and performing the investigation.
1. Compare the science investigation skills (SIS) codes in the four curriculum expectations
associated with this video. How may the difference in these codes impact your
preparation for student investigations?
SBI3C C2.3 prepare a SBI3C C2.5
SNC4M C2.4 use an
SNC4E D2.2 conduct
laboratory culture of
investigate and
inquiry process to
an investigation,
microorganisms (e.g., analyse the conditions demonstrate the effect using safe practices
acidophilus) on agar, (e.g. optimal
of the use of sterile
and aseptic
using proper aseptic
temperature) needed
techniques (e.g.,
techniques, to
techniques [PR]
by microorganisms
pasteurization, use of compare the
for growth [PR, AI]
an autoclave) on
characteristics and
pathogenesis [IP, PR] growth of different
types of nonpathogenic bacteria
[PR, AI]
The SNC4M C2.4 expectation requires that students be involved in the planning of the
procedure to be used. To ensure safety the teacher should review the students’ plans
paying special attention to concentration and volume of reagents, and the choice of heat
source (if any) that they wish to use.
Classroom management considerations may also change depending on the course and the
number of students enrolled.
2. What are the steps involved in properly lighting a Bunsen burner?
Check rubbing tubing and securely fasten it to the gas outlet.
Check striker to ensure that there is adequate flint to easily produce sparks (or use a BBQ
lighter).
Close the air intake on the Bunsen burner completely.
Turn on the gas to full.
Hit striker (using both hands can make this easier) over the mouth of the Bunsen burner.
Adjust the air intake to get the desired flame. (Note that yellow flames are more easily
seen, but blue flames are more efficient for sterilization.)
3. What should you consider when selecting gloves for an activity?
Allergies of your students (latex allergies are becoming more common).
Permeability of the material to the chemicals being used, and the length of time the
gloves will be worn.
4. Why is a plastic squirt bottle preferred over a beaker as the ethanol container used in this
investigation to disinfect the work surface?
Squirt and spray bottles are preferable, because they will not spill as easily if accidently
knocked over. Additionally, fewer vapours will be released when sealed containers are
used, and the risk of sparks falling onto the flammable liquids and igniting them is
removed.
5. What are the advantages of using bleach and QUAT solutions instead of ethanol as
disinfectants? What are the disadvantages?
Advantages: Working with flammable liquids such as ethanol and an open flame requires
a certain level of student skill and maturity. Bleach and QUAT solutions are more readily
available and are not flammable.
Disadvantages: Bleach is more hazardous if exposed to the skin than ethanol, and also
runs the risk of damaging clothing and plastic ware. QUAT tends not to be as effective
against a broad range of microorganisms, and takes longer to disinfect, without the
addition of an alcohol. When comparing ethanol, 10% bleach and QUAT solutions,
ethanol is the least damaging when it comes into contact with skin or clothing.
6. Why should the work space be disinfected before lighting the Bunsen burner?
To increase the distance, both physically and temporally, between the open flame and any
flammable liquids or their vapours in the classroom.