FLAME TEST PRACTICAL TASK
(DCP)
Background Knowledge
(Refer to task sheet)
Aim
To identify each of the unknown samples presented as a specific salt through the observation of
flame colours.
Hypothesis
N/A
Apparatus
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Bunsen burner
Gauze mat
Rubber tube
Matches
HCl solution
Salt samples
Small beaker (with water)
Nichrome wire
Watch glasses
Spatula
Safety
In order to conduct a safe experiment, certain precautions must be taken into account. These are:
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Wearing a lab coat, important to avoid damage to skin and clothes if acid is split
Tying long hair back, important to lower the risk of hair catching fire while using the
Bunsen burner
Placing the Bunsen burner on a gauze mat, important to avoid burning the desk
Firmly push the rubber tube (from the Bunsen burner) into the gas outlet, important to avoid
gas leaks and fire risk
Ensure that the air port is closed when lighting the Bunsen burner, important to ensure that
the flame is a ‘safe flame’ and is clearly visible (lower fire risk)
Place the Bunsen burner flat in the centre of the bench (on the gauze mat), important to
ensure that the Bunsen burner does not slide off the edge of the bench
Clear the area of any books, papers or other objects that aren’t needed for the experiment,
this is important to avoid fire risks
Ensure that neither the Bunsen burner or the rubber tube have any cracks or holes, important
to lower the fire hazard
Do not leave open flames unattended, important to lower the risk of an accident and a fire
Turn off the gas when the experiment is complete, important to avoid gas leaks and fire risk
Allow the Bunsen burner to cool down before handling, important to avoid burns
Wear safety glasses, important to avoid contact between the acid and the experimenter’s
eyes
Light the match before turning on the gas, important as to avoid a large flame because of
excessive gas
Method
Independent Variable: Salt being tested
Dependent Variable: Flame colour
Controlled Variables: N/A
Control Sample: N/A
1. Clean a nichrome wire by dipping into HCl solution. Heat the wire in the heating flame of a
Bunsen until no more colour is produced.
2. Mix a little of the salt to be tested with the acid solution on a watch glass and dip the
end of the clean wire in the solution.
3. Hold this end of the wire in the outer blue part of the flame and note any flashes of colour
that may appear and the intensity. Note that these may fade quickly.
4. Test subsequent salts in the same manner, cleaning the wire between each test as described
in #1.
5. Tabulate your results making sure to include qualitative and quantitative data.
6. Use the information you have collected to identify the cations in each of the unknown
samples provided to you.
Results
Sample Name
Colour Produced
Intensity
NaCl
Bright orange
Very intense
CuCl₂
Strong blue and
green, sharp
stream of white
in centre
Bright white
Very intense
MgCl₂
White sparks at
beginning, then
blue and green
Moderately
Intense
KCl
Pink/ Orange/
Purple
Blood Orange
Moderately
Intense
Very Intense
Predominantly
pink, some red
Very Intense
FeCl₃
CaCl
LiCl
Very intense
Time the colour
lasted for
Lasted for a very
long time (2
minutes+)
All colours lasted a
short amount of time
(15 seconds)
Other Notes/
Observations
Cloudy texture
Lasted a short
amount of time (10
seconds)
Lasted a short
amount of time (10
seconds)
Harsh sparks
Lasted a long time
(2 minutes+)
Lasted a long time
(2 minutes+)
Lasted a long time
(2 minutes+)
Began green and
blue, white stream
appeared
Formed white
powder/ salt on
wire, sparks not
very intense
A little cloudy
BaCl₂
Green
Not very
intense
Strontium Cl
Predominantly
red, some pink
Very Intense
Unknown A
Yellow/ Orange
Very Intense
Unknown B
Green
Not very
intense
Lasted a very short
amount of time (2
seconds)
Lasted a short
amount of time (5
seconds)
Lasted a long time
(2 minutes+)
Lasted a very short
amount of time (2
seconds)
Formed a solid
grey salt on the
wire
Formed a solid
grey salt on the
wire
From the observations, it looks as though unknown A is NaCl and unknown B is BaCl2.
Discussion
There were no obvious trends in my results. Each of the different salts had a different reaction
and the colours were all quite evenly varied, each appearing two to three times. The intensity of
the flame produced was just as varied as the colours, and so with the amount of time that the
flames lasted for.
Unknown A and NaCl produced very similar results, as with unknown B and BaCl2.
These trends (or lack of trends) are due to the fact that apart from the unknowns, all of the
samples were different, and so produced different results.
Evaluation
My data is moderately reliable. On one hand, all of my data was taken from observation, judgement
and estimation. I observed the flame colours (and in some cases the texture of the flame or the
aftermath), judged whether the flames produced were intense or not, and estimated the amount of
time that each of the colours lasted for. This could make my data somewhat unreliable since it is
personal judgement and may be subjected to human error or bias (random error).
On the other hand, I worked closely with another student (Celene) since we were working next to
each other, and we frequently compared results. Having another opinion and a second set of
observations and judgements significantly reduced the chance of random error. This was because if
Celene and I produced obvious differences in our observations of the same substance, we would
repeat the test and record the results that were constant for both of us.
One strength of my design was the table I created before completing the experiment. Having an in
depth and clear table allowed me to come out of the experiment with thorough observations. This was
very useful when it came to identifying the two unknown substances, since I had recorded
observations for more than just the colour produced. If I had only recorded the colour, I may have
found it more difficult since some of the substances produced the same colour.
A second strength of my design was the safety section. Having not used a Bunsen burner for a while,
I found it very helpful to review the method of using Bunsen burners and safety precautions before
I began the practical. This way, not only did I avoid accidents, but I was able to set up and
complete my practical quickly and thoroughly because I didn’t have to spend any time figuring out
how to use the equipment.
One improvement that could be made to this experimental design would be to use a stopwatch to time
how long the flame colours produced last for. This would allow for more precise results and help to
identify the unknowns.
A second improvement that could be made to this experimental design would be to repeat the tests.
Some groups had trouble recording accurate results because some of the salt samples had fallen
inside of the Bunsen burner and had therefore had an impact on some of the flame colours produced
with subsequent salt samples. If the Bunsen burners were cleaned and the tests repeated twice more,
this would eliminate the problem.
This method was valid, as it allowed me to collect all the data I needed in order to identify
unknown A and B. As mentioned before, timing the flames with a stopwatch could be an improvement,
however, it is not essential, as the observational techniques I used were sufficient.
Having completed this experiment, I am inspired to further investigate how the different flame
colours are produced and if flame colours are produced with other salts (if so, what colours).
Conclusion
A hypothesis was not applicable for this particular experiment. However, through the observation of
flame colours in different salts, I have come to the conclusion that unknown A is NaCl and that
unknown B is BaCl2.
ATOMIC SPECTRA PRACTICAL
TASK (DCP)
Background Knowledge
(Refer to task sheet)
Aim
To calculate frequency and energy values of specific wavelengths by observing and recording the
line spectra of hydrogen gas.
Hypothesis
N/A
Apparatus
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Spectrometer
White light source
Hydrogen gas discharge tube (set up prior to the experiment)
Safety
In order to conduct a safe experiment, certain precautions must be taken into account. These are:

Not touching the hydrogen gas tube, in order to prevent injury or damage to the materials
(There are no more safety requirements for this experiment)
Method
Independent Variable: Type of light being tested
Dependent Variable: Wavelengths produced
Controlled Variables: Spectrometer used
Control Sample: N/A
1. Go to the station where a hydrogen gas discharge tube is set up. Here, an induction coil is
being used to provide energy to “exite” the gas atoms.
2. Using the spectrometer, look at one of the fluorescent light in the room. You will see
coloured lines corresponding to specific wavelengths emitted by the white light.
3. Record the values for the violet and green lines. These should be 4360 Å and 5460 Å
respectively. Note any error in these readings so that adjustments can be made in subsequent
readings.
4. Turn on the electricity to the hydrogen gas tube (for no more than 30 sec at one time to
prevent burn out).
5. Look through the spectrometer and observe/record the coloured lines that are produced.
6. Tabulate your results, including qualitative and quantitative data.
7. Process your data thoroughly, providing as much information as possible about each line
found including error and uncertainty.
Results
White Light
Hydrogen Gas Tube
Colour of Line
Wavelength (Å ±50)
Dark Purple
Violet
Dark Green
Light Green
Orange
Red
Purple
Green
Yellow
Red
4200
4400
4900
5500
5900
6100
4400
5500
5800
6500
Wavelength (m± 50 x 1010
)
4200 x 10-10
4400 x 10-10
4900 x 10-10
5500 x 10-10
5900 x 10-10
6100 x 10-10
4400 x 10-10
5500 x 10-10
5800 x 10-10
6500 x 10-10
(Qualitative): The lines produced by white light were a lot thicker than those produced by the
hydrogen gas tube, which were sharp and thin.
Calculations:
E = energy (J or kJ)
h = Planck’s constant = 4.00 x 10-13 kJ.s.mol-1
v = frequency (Hz or s-1)
c = speed of light = 3.00 x 108 m.s-1
λ = wavelength (nm, cm, Å)
Frequency
÷λ
c = λv -> v = c
Energy
E = hv
White light
Dark Purple: E = (4.00 x 10-13 kJ.s.mol-1) x (7.14
x 10-14 s-1)
E = 2.86 x 10-26 kJ
Violet: E = (4.00 x 10-13 kJ.s.mol-1) x (6.82 x
10-14 s-1)
E = 2.73 x 10-26 kJ
Dark Green: E = (4.00 x 10-13 kJ.s.mol-1) x (6.12
x 10-14 s-1)
E = 2.45 x 10-26 kJ
Light Green: E = (4.00 x 10-13 kJ.s.mol-1) x (5.45
x 10-14 s-1)
E = 2.18 x 10=26 kJ
Orange: E = (4.00 x 10-13 kJ.s.mol-1) x (5.08 x
10-14 s-1)
E = 2.03 x 10-26 kJ
Red: E = (4.00 x 10-13 kJ.s.mol-1) x (4.92 x 10-14
s-1)
E = 1.98 x 10-26 kJ
Hydrogen Gas Tube
Purple: E = (4.00 x 10-13 kJ.s.mol-1) x (6.82 x
10-14 s-1)
E = 2.73 x 10-26 kJ
Green: E = (4.00 x 10-13 kJ.s.mol-1) x (5.45 x 1014
s-1)
E = 2.18 x 10=26 kJ
Yellow: E = (4.00 x 10-13 kJ.s.mol-1) x (5.17 x
10-14 s-1)
E = 2.07 x 10-26 kJ
Red: E = (4.00 x 10-13 kJ.s.mol-1) x (4.62 x 10-14
s-1)
E = 1.85 x 10-26 kJ
Wavelength (m± 50 x 10-10) Frequency (s-1)
Energy (kJ)
White light
Dark Purple: v = (3.00 x 108 m.s-1) ÷ (4200 x
10-10m)
v = 7.14 x 10-14 s-1
Violet: v = (3.00 x 108 m.s-1) ÷ (4400 x 1010
m)
v = 6.82 x 10-14 s-1
Dark Green: v = (3.00 x 108 m.s-1) ÷ (4900 x
10-10m)
v = 6.12 x 10-14 s-1
Light Green: v = (3.00 x 108 m.s-1) ÷ (5500 x
10-10m)
v = 5.45 x 10-14 s-1
Orange: v = (3.00 x 108 m.s-1) ÷ (5900 x 1010
m)
v = 5.08 x 10-14 s-1
Red: v = (3.00 x 108 m.s-1) ÷ (6100 x 10-10m)
v = 4.92 x 10-14 s-1
Hydrogen Gas Tube
Purple: v = (3.00 x 108 m.s-1) ÷ (4400 x 1010
m)
v = 6.82 x 10-14 s-1
Green: v = (3.00 x 108 m.s-1) ÷ (5500 x 10-10m)
v = 5.45 x 10-14 s-1
Yellow: v = (3.00 x 108 m.s-1) ÷ (5800 x 1010
m)
v = 5.17 x 10-14 s-1
Red: v = (3.00 x 108 m.s-1) ÷ (6500 x 10-10m)
v = 4.62 x 10-14 s-1
White Light
Hydrogen Gas
Tube
Colour of
line
Dark Purple
Violet
Dark Green
Light Green
Orange
Red
Purple
Green
Yellow
Red
4200
4400
4900
5500
5900
6100
4400
5500
5800
6500
x
x
x
x
x
x
x
x
x
x
10-10
10-10
10-10
10-10
10-10
10-10
10-10
10-10
10-10
10-10
Absolute uncertainty = ±50
Percentage uncertainty
White Light: Dark Purple (50 ÷ 4200)
Violet
(50 ÷ 4400)
Dark Green
(50 ÷ 4900)
Light Green (50 ÷ 5500)
Orange
(50 ÷ 5900)
Red
(50 ÷ 6100)
Hydrogen G.T: Purple
(50 ÷ 4400)
x
x
x
x
x
x
x
100%
100%
100%
100%
100%
100%
100%
7.14
6.82
6.12
5.45
5.08
4.92
6.82
5.45
5.17
4.62
=
=
=
=
=
=
=
x
x
x
x
x
x
x
x
x
x
10-14
10-14
10-14
10-14
10-14
10-14
10-14
10-14
10-14
10-14
2.86
2.73
2.45
2.18
2.03
1.98
2.73
2.18
2.07
1.85
x
x
x
x
x
x
x
x
x
x
10-26
10-26
10-26
10=26
10-26
10-26
10-26
10=26
10-26
10-26
1.19%
1.14%
1.02%
0.91% Percentage Error
0.85% White Light:
Violet (4200 – 4000) ÷4000 x 100% =
0.82%
5.00%
1.14%
Red (6100 – 7000) ÷7000 x 100% =
12.86%
Green
Yellow
Red
(50 ÷ 5500) x 100% = 0.91%
(50 ÷ 5800) x 100% = 0.86%
(50 ÷ 6500) x 100% = 0.77%
[A graph is not relevant or necessary for this particular set of data]
Discussion
A trend that I noticed in my results was that the shorter the wavelength of a certain colour, the
greater the amount of energy. This is the same with frequency, shorter wavelengths produced higher
frequencies.
These are both evidence of Planck’s conclusion that the amount of energy is inversely related to
the wavelength of light (the same goes for frequency).
Evaluation
My data may is moderately reliable. On one hand, it followed the general trends that are suggested
by Planck and the results are fairly logical. On the other hand, however, there may have been a
fault at the data collection stage. This is because although the values I collected make sense,
they are quite far from the accepted values.
A strength of my design was the table. Having this already prepared before my prac made it quick
and easy for me to record the measurements while I was doing the prac. An improvement that I could
make would be to familiarise myself with the formulas and conversion a bit more thoroughly before
completing the prac because it would have deepened my knowledge and also cut down the calculation
time.
Having done this experiment, I am inspired to investigate the wavelength, frequency and energy of
light in other ways and using other types of equipment.
Conclusion
A hypothesis was not applicable for this particular experiment. However, I was able to calculate
frequency and energy values of specific wavelengths by observing and recording the line spectra of
hydrogen gas (see calculations above).