H.
BTEC L3 EXTENDED DIPLOMA IN APPLIED SCIENCES
Unit 2: Practical Scientific Procedures and
Techniques
Assignment 2A: Concentrate on keeping up your
standards
Laboratory equipment and its calibration
What is calibration?
Calibration is the scientific process of making comparisons between
measurements, by determining the relationship between values through
measurements and indications on a measuring instrument. This process is
performed in order to decrease any measurement uncertainty by guaranteeing
the accuracy of equipment.
Method to calibrate pH probe
Firstly, turn on the pH probe and thoroughly wash the pH probe with distilled
water in a sink.
Next, you must set up buffers to calibrate the pH probe. The first buffer solution
should be a neutral pH of 7, the second buffer solution should be close to the
estimated sample pH, e.g. pH 4 or 9po, depending on the whether the sample is
a base/acid and the third buffer solution should be one lower than the estimated
sample pH. For example, the buffer solutions I used for the calibration of the pH
probe was 6.86, 9.18 and 4.01. Once set up, leave the buffers to arrive at the
same temperature as the pH probe because pH changes with temperature,
therefore is temperature-dependent. Add the buffers into separate beakers in
order to calibrate the pH probe.
Following on from the last step, put the pH probe in the first beaker with the
neutral pH, and start the reading. To start the reading, push the
‘measure’/’calibrate’ button when the pH probe is placed in the beaker. Leave
the pH reading to settle before allowing it to set for around 1-2 minutes.
After attaining a stable reading, set the pH probe to the buffer’s pH by pushing
the ‘measure’ button again. Once this is done, wash the pH probe thoroughly
with distilled water, as done in the first step.
Put the pH probe in the next beaker and follow the same steps as the first
beaker, washing the pH probe when done.
Method to calibrate a burette/pipette
Firstly, to calibrate a pipette, ensure that it is completely clean and dry, as well
as empty, before calibration.
Following on to the next step, it involves using distilled water and you will need
to accurately measure the temperature of the distilled water using a
thermometer. To make sure the temperature obtained is accurate, leave the
thermometer in the water for at least 10 minutes.
1
, H.
BTEC L3 EXTENDED DIPLOMA IN APPLIED SCIENCES
Unit 2: Practical Scientific Procedures and
Techniques
Once the temperature is obtained, weigh a clean and dry beaker with a balance
(should be calibrated before). Then, use a pipette filler to extract the distilled
water until the 25ml graduation mark and transfer it to the beaker you have
weighed carefully. Next, record the mass of the beaker with the water using the
balance and repeat this step twice to obtain an average of the masses recorded.
Following on from the last step, you need to calculate the volume released by
the pipette using the formula volume = mass/density. The temperature obtained
from the distilled water is used to find the density of the water. For example, in
my calibration of the pipette, the temperature was 25 degrees Celsius which
meant the density was 0.996262. Once you have attained the density of the
water, you can use this with the average mass of all the readings you took on the
balance with the beaker of water. You will need to divide the average mass of
water by the density of the water and this value will be the volume released by
the pipette. For example, I calculated the average mass to be 26.0g and divided
this by the density of water – 26.0/0.996262 = 26.097 = 26.1 cm 3
Method to calibrate a balance
Firstly, place the balance on a flat surface and turn on the balance Figure 2 – Image of a
by pushing the ‘on/off’ button. balance being calibrated
with weights
Secondly, press and hold the ‘cal’ button on the balance in order to
calibrate the balance. When the balance display shows ‘cal 0’, let go of
the ’cal’ button. Then add 1-5 100g weight(s) onto the balance, and
wait for a reading on the balance display (as shown in Figure 2). If the
reading display shows the correct balance of the weight(s), e.g.2 x
100g weights should show 200g, press the ‘cal’ button again to confirm
the weight, allowing the balance to calibrate. If the weight shown on
the display is not correct, repeat the steps above until the weight
shown is correct.
Importance of calibrating equipment before undertaking an investigation
It is important to calibrate equipment beforehand as it determines the accuracy
and quality of results produced by equipment. As equipment is used over long
periods of time, the accuracy of results may shift especially when using
technologies, hence why calibration is necessary for equipment. To make sure
that the results we are producing are both accurate and reliable, we need to
continuously calibrate equipment before we carry out experiments.
The use of calibration is to reduce any uncertainties in measurements by
establishing the accuracy of equipment used. Therefore, calibration is important
as it allows us to control any errors/uncertainties that may be present within
measurements.
Examples of where calibration is important:
2
BTEC L3 EXTENDED DIPLOMA IN APPLIED SCIENCES
Unit 2: Practical Scientific Procedures and
Techniques
Assignment 2A: Concentrate on keeping up your
standards
Laboratory equipment and its calibration
What is calibration?
Calibration is the scientific process of making comparisons between
measurements, by determining the relationship between values through
measurements and indications on a measuring instrument. This process is
performed in order to decrease any measurement uncertainty by guaranteeing
the accuracy of equipment.
Method to calibrate pH probe
Firstly, turn on the pH probe and thoroughly wash the pH probe with distilled
water in a sink.
Next, you must set up buffers to calibrate the pH probe. The first buffer solution
should be a neutral pH of 7, the second buffer solution should be close to the
estimated sample pH, e.g. pH 4 or 9po, depending on the whether the sample is
a base/acid and the third buffer solution should be one lower than the estimated
sample pH. For example, the buffer solutions I used for the calibration of the pH
probe was 6.86, 9.18 and 4.01. Once set up, leave the buffers to arrive at the
same temperature as the pH probe because pH changes with temperature,
therefore is temperature-dependent. Add the buffers into separate beakers in
order to calibrate the pH probe.
Following on from the last step, put the pH probe in the first beaker with the
neutral pH, and start the reading. To start the reading, push the
‘measure’/’calibrate’ button when the pH probe is placed in the beaker. Leave
the pH reading to settle before allowing it to set for around 1-2 minutes.
After attaining a stable reading, set the pH probe to the buffer’s pH by pushing
the ‘measure’ button again. Once this is done, wash the pH probe thoroughly
with distilled water, as done in the first step.
Put the pH probe in the next beaker and follow the same steps as the first
beaker, washing the pH probe when done.
Method to calibrate a burette/pipette
Firstly, to calibrate a pipette, ensure that it is completely clean and dry, as well
as empty, before calibration.
Following on to the next step, it involves using distilled water and you will need
to accurately measure the temperature of the distilled water using a
thermometer. To make sure the temperature obtained is accurate, leave the
thermometer in the water for at least 10 minutes.
1
, H.
BTEC L3 EXTENDED DIPLOMA IN APPLIED SCIENCES
Unit 2: Practical Scientific Procedures and
Techniques
Once the temperature is obtained, weigh a clean and dry beaker with a balance
(should be calibrated before). Then, use a pipette filler to extract the distilled
water until the 25ml graduation mark and transfer it to the beaker you have
weighed carefully. Next, record the mass of the beaker with the water using the
balance and repeat this step twice to obtain an average of the masses recorded.
Following on from the last step, you need to calculate the volume released by
the pipette using the formula volume = mass/density. The temperature obtained
from the distilled water is used to find the density of the water. For example, in
my calibration of the pipette, the temperature was 25 degrees Celsius which
meant the density was 0.996262. Once you have attained the density of the
water, you can use this with the average mass of all the readings you took on the
balance with the beaker of water. You will need to divide the average mass of
water by the density of the water and this value will be the volume released by
the pipette. For example, I calculated the average mass to be 26.0g and divided
this by the density of water – 26.0/0.996262 = 26.097 = 26.1 cm 3
Method to calibrate a balance
Firstly, place the balance on a flat surface and turn on the balance Figure 2 – Image of a
by pushing the ‘on/off’ button. balance being calibrated
with weights
Secondly, press and hold the ‘cal’ button on the balance in order to
calibrate the balance. When the balance display shows ‘cal 0’, let go of
the ’cal’ button. Then add 1-5 100g weight(s) onto the balance, and
wait for a reading on the balance display (as shown in Figure 2). If the
reading display shows the correct balance of the weight(s), e.g.2 x
100g weights should show 200g, press the ‘cal’ button again to confirm
the weight, allowing the balance to calibrate. If the weight shown on
the display is not correct, repeat the steps above until the weight
shown is correct.
Importance of calibrating equipment before undertaking an investigation
It is important to calibrate equipment beforehand as it determines the accuracy
and quality of results produced by equipment. As equipment is used over long
periods of time, the accuracy of results may shift especially when using
technologies, hence why calibration is necessary for equipment. To make sure
that the results we are producing are both accurate and reliable, we need to
continuously calibrate equipment before we carry out experiments.
The use of calibration is to reduce any uncertainties in measurements by
establishing the accuracy of equipment used. Therefore, calibration is important
as it allows us to control any errors/uncertainties that may be present within
measurements.
Examples of where calibration is important:
2
