Undergraduate Risk Assessment Form
Experiment
Student
Supervisor
Course
Date
Hydrogen-oxygen mini rockets
Year 12 school students (n<20)
Joanne Elliott
Highest Risk Code
Med
Fume cupboard
Gloves
Outreach
17/12/12
N
N
Outline of experimental procedure
The activity is designed to take 2 hours to complete. The activity is laboratory based and will
be supervised throughout and full instructions will be given. The activity is based on a wellknown demonstration: the hydrogen-oxygen combustion reaction.
Stage 1) Testing the effect of the ratio of gases (hydrogen and oxygen) upon combustion:
Pre-prepared hydrogen and oxygen filled balloons attached to a thick glass conical flask with a
ground glass neck will be supplied. The conical flasks will be sealed with a rubber septum
pierced with a blunted syringe tip attached to a plastic extraction syringe. These hydrogen and
oxygen balloons will be filled beforehand by technical staff and taken to the event location.
~5-10 ml of soap solution is placed in a plastic well using a plastic pipette. A small plastic
syringe (2.5 ml volume) is filled with varying ratios of hydrogen and oxygen (from controlled
sources) to give a total volume of ~2 ml. Students will be shown how to fill the syringe with
small volumes of hydrogen and oxygen by a demonstration at the start of the session. The
syringe containing the mixture of hydrogen and oxygen is emptied into the soap solution to
create a raft of bubbles. Using a lit match the raft of bubbles is ignited. The activity is repeated
to correlate the ratio of gases with how loud the sound is upon ignition. The sound is expected
to vary from small pops to loud cracks.
Stage 2) Preparing and launching the mini rocket:
Pre-prepared hydrogen and oxygen filled balloons attached to a thick glass conical flask with a
ground glass neck will be supplied. The conical flasks will be sealed with a rubber septum
pierced with a blunted syringe tip attached to a plastic extraction syringe. These hydrogen and
oxygen balloons will be filled beforehand by technical staff and taken to the event location.
A pre-prepared launcher (an inverted small plastic lid with a copper ignition wire and fixed
syringe for gas extraction) is filled with a liquid, baby oil or custard (this is the ejector liquid);
the launcher is attached to a metal retort stand for stability. A plastic pipette is cut with
scissors to leave just the pipette bulb and a short stem (this is the rocket). A small plastic
syringe is filled with varying ratios of hydrogen and oxygen to give a total volume of 5 ml and
the gas mixture (this is the fuel) is transferred to the rocket. Students will be shown how to fill
the syringe with small volumes of hydrogen and oxygen by a demonstration at the start of the
session. The rocket is then inserted into the launcher. A small amount of fuel is then extracted
from the rocket causing the ejector liquid to seep inside the base of the rocket forming a gas
tight seal.
The rocket is launched by taking the metal stand and the launcher to a designated launch area
(an area taped off from other parts of the lab where the floor is covered with absorbent material
(bench coat for example). The launcher is angled and directed along the designated flight path
and crocodile clips are used to connect the ignition wires to a piezoelectric gas lighter, pressing
the ignition button will launch the mini rocket. The spark from the gas lighter will ignite the
gas mixture propelling the rocket forwards, as the rocket is propelled forwards the ejector liquid
will be expelled from the rocket. The sound associated with rocket launch is expected to vary
from small pops to loud cracks; the rocket is expected to travel up to 8 m.
Undergraduate Risk Assessment Form
Substance
Soap solution
Oxygen source (small balloon prefilled with oxygen) attached to a
conical flask via a rubber septum, with
a plastic extraction syringe in place
Hydrogen source (small balloon prefilled with hydrogen) attached to a
conical flask via a rubber septum with
a plastic extraction syringe in place
Quantity
100 mL
1000 ml
Hazard description
Irritant
Oxidising
Risk code
Low
Low
1000 ml
Medium
Hydrogen oxygen mixtures contained
in a syringe/mini rocket
6 ml
Custard
Baby oil
10 ml
10 ml
Extremely flammable,
ignition may result in
explosion with oxygen in
air causing burns and a
very loud noise
Explosive mixtures may
cause burns and a loud
noise upon ignition
No chemical hazard
No chemical hazard
Low
Low
Low
Precautions and control measures
Students, demonstrators and staff at the event may be affected by the following:
Hazard: Burns caused by matches
Control measures: It is expected that students will be familiar with the use of matches however
the lighting of matches and their subsequent disposal will also form part of the initial
demonstration. Matches are considered to be the safest choice of ignition source (short lived).
Matches to be disposed of in a small glass beaker containing a small volume of water on the
bench.
Hazard: Ear damage caused by explosion of hydrogen-oxygen mixtures, soap bubbles and
mini rocket
Control measures - The controlled combustion of mixtures of hydrogen and oxygen will only be
performed on a small scale < 5 cm3 total volume. The explosion of larger volumes is hazardous
and can lead to damage, however small volumes should only give rise to a loud crack. 2.5 ml
syringes to be supplied for this activity thus limiting the amount of combustible gas available.
Hazard: Eye damage caused by explosion of hydrogen-oxygen mixtures, soap bubbles and
mini rocket
Control measures - Eye protection will be worn throughout. The controlled combustion of
mixtures of hydrogen and oxygen is only to be performed on a small scale < 5 cm3 total
volume.
Hazard: Physical damage caused by explosion of hydrogen-oxygen mixtures, soap bubbles
and mini rocket
Control measures - The controlled combustion of mixtures of hydrogen and oxygen is only to
be performed on a small scale < 6 cm3 total volume. Soap bubble mixture is to be ignited with
a match; Care to be taken when handling lit matches and with their disposal. Mini rocket
ignition is to be performed in a separate, well defined area, ignition to be carried out remotely
by use of a piezoelectric lighter; Help is to be provided with the mini-rocket ignition,
designated demonstrator to be in position for this part of the activity.
Hazard: Skin damage caused by syringe or broken glassware
Control measure – syringe tips will be pre-blunted. Syringe needle already piercing the rubber
septum to avoid risk associated with piercing rubber with fine needles. Glassware will only
break if significant impact occurs; this is unlikely to occur as there is no need to move
Undergraduate Risk Assessment Form
glassware around. If glassware does break the gases will dissipate and the broken glass can be
swept up using a dust pan and brush or other suitable cleaning equipment.
Hazard: Ear, eye and physical damage caused by exploding hydrogen balloon
The hydrogen containing balloon will explode with oxygen in the air if ignited, causing a very
loud bang (~4 to 75% hydrogen in air is explosive).
Control measure: To minimise the risk of this happening the hydrogen balloon will be kept at
least 1-2 m away from the ignition source (matches, piezoelectric lighter) and only a small
volume of hydrogen (< 1 dm3) per student team will be available. Eye protection will be worn
throughout.
Hazard: Nearby combustibles igniting
Control measure: Area to be kept clean from likely combustibles (tissue for example), only
small volumes of gas to be ignited limited by size of syringe. Fire fighting equipment is on hand
as are trained operatives.
Hazard: Physical damage caused by carrying the launch stage
Control measure: No sharps on launch stage. The stage is easy to carry being a standard
laboratory retort stand.
Hazard: Slippage on wet floor by mini rocket launch area
Local floor will be covered with absorbent material (e.g. bench coating) to minimize hazard.
Hazard: Physical damage due to being hit by a mini rocket
Control measure – The launch area and flight path will be clearly defined (~2 m wide and ~12
m long); the person launching the rocket will be made aware of the hazard and will note a clear
flight path prior to launch. Mini rocket is light weight and unlikely to cause physical damage.
Eye protection will be worn throughout.
Technical staff may be affected by the following:
Hazard: Physical damage caused by hydrogen and oxygen compressed gas cylinders used
to pre-fill the balloon systems.
Control measure: Gas cylinders provided by BOC. Appropriate regulators used, fitted and
controlled by staff trained in gas cylinder/gas regulator handling. Gas cylinders to be held in
safety stands. Trained staff to oversee storage and use of cylinders at all times. MSDS to be
checked beforehand.
Hazard: Physical damage caused by transportation of equipment
Control measure: Trolleys to be used to transport equipment. Two people per trolley, one to
ensure a clear travel path and one to push the trolley.
Students may be affected by the following:
Hazard: Physical damage caused by attempts to repeat the activity at home
Control measure: Students advised against this during the session. Unlikely to occur as access
to suitable gas supplies is not obvious.
The above hazards have been noted and all necessary precautions to control and limit
these hazards have been taken. The experiment has been tested a number of times ‘inhouse’ and all staff and student demonstrators have conducted the complete experiment
at least once. All students, participants and staff to wear lab glasses throughout.
Waste Disposal
The waste from all experiments will be collected by the staff after the day’s activities and
disposed of accordingly.
Undergraduate Risk Assessment Form
Data For High Hazard category chemicals when > 1g and used in an open system or > 100 g
Substance
Quantity
Hazard
Category
Activity
Exposure Scores
A
B
C total
Exposure
potential
Risk Code
No High Hazard
chemicals used
Additional Notes
Activity is to be supervised throughout (~3 staff and ~2 student helpers will be present), an introductory talk highlighting the hazards will be given at the
beginning, and the activity will also be demonstrated at the start of the event.