Unit 2- Practical Scientific Procedures and Techniques
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PEARSON (PEARSON)
Unit 2 assignment, it contains part A of assignment unit 2 Practical Scientific Procedures and Techniques of BTEC applied science. i gained a DISTINCTION for this assignment, the assignment includes: Preparing a standard solution of sodium carbonate solution, a titration experiment, and also colori...
Unit 2- Practical Scientific Procedures and Techniques
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Calibration of a balance
Here are instructions on how to calibrate a balance, we should calibrate the balance
regularly using standard weights to ensure our measurements are precise which is
important when conducting an experiment in the laboratory.
Equipment
Top pan balance- to calibrate and weigh.
Tweezers- to pick up standard weights.
Cloth if needed to wipe scale.
Standard weights – to place on balance and weigh.
Preparation
Make sure balance is clean weight a dry cloth to remove any particles and get
accurate measuring.
Prepare the weight you will be using for calibration and make sure they are clean
too with a cloth to remove any particles that may affect reading of weight.
Ensure your setup area is away from draughts as it may affect the reading, a way
to do this is by using a balance with screen slides around it this stops this stops
draughts affecting the measurements. Another way is closing windows and doors
if it is a windy day to have reliable results at it excludes any possible draughts.
Avoid wearing or having anything magnetic around the balance as it can affect
the balance precious.
Ensure the balance is in an area where there are no vibrations for example
people walking around in laboratory. This is another factor that may affect the
precision of the balance, which you would want to exclude to have reliable results
when calibrating.
Procedure
1) Turn1 on the balance. Make sure it is not at the edge of the table to prevent it
from falling.
2) Allow for its ‘warm up' time if needed.
3) Make sure the surface is flat and levelled, this in ensures your measuring
accurately.
4) On the balance there should be a bottom saying CAL (this is calibration mode).
1
Philip Harris https://www.philipharris.co.uk/blog/secondary/how-to-calibrate-an-electronic-balance/
1
, 5) Once pressed on the screen should appear CAL on screen.
6) Next press the on/off zero button – this will zero the balance and will display ‘C’
on the screen.
7) The screen will then display a number of grams on the screen ‘C 200’
200g is the maximum you can weigh up to. If you go over it can damage the
balance which will not make your measurements reliable.
8) This will ensure you that it’s on the right mode and ready to start.
9) Using a tweezers place your first weight (as selected) at the centre on the
balance making sure it’s stable and ensure it reads what it weighs correctly. The
use of tweezers will prevent particles from your hand to the weights. This enables
you to have accurate measurements.
10)Use the tweezers to remove weight off the balance. When it is removed is should
read zero grams. Once you see this add the same weight back on, to ensure
correct and accurate reading.
11)Continue to add more mass of weights until you have done a range of weights
that will cover the amount you will be measuring in the experiment.
12)Ensure you record your results.
Making a standard solution
Here are the equipment’s I used for this practical including its uses , I had to ensure I
had these before starting the practical.
Equipment for standard solution
Glass2 stirring rod- this is used to stir a solution for it to dissolve. A limitation is
that its fragile as it is made from glass so it’s easy to break. To overcome this
limitation, students should be aware that it if fragile, so to handle it with care.
2
(No author ) practical chemistry
https://practical-chemistry.com/practical-work/chemistry/quantitative-chemistry/making-a-standard-solution/
2
, Balance- this is used to weigh the solute or substance. A limitation is that if it is
not calibrated it may not give accurate measurements. To overcome this
limitation ensure you calibrate the balance first.
Safety goggles- this is for the safety of participants undertaking this experiment
but can be taken off when measuring the meniscus for accuracy.
250 cm3 and 100 cm3 beaker- this has a multi-purpose usage as it can be used to
measure a volume if you do not want to be too precise, so it’s not accurate which
can be seen as a limitation. However, it is mainly used to mix substances and
dissolve solutions.
250 cm3 Volumetric3 flask with stopper – this is highly accurate as it has a fixed
volume of a substance, therefore great used for measuring. It also has a narrow
neck which is useful when you want to shake the solution. A way to use this is by
pouring your solution inside the volumetric flask until you get close to the marked
line. This is where you will make sure you are eye levelled and close to the
volumetric flask and observe the meniscus and use a pipette to slowly add the
solution until the meniscus reaches the marked line. One limitation is that it has
a fixed volume so you cannot use it to measure any other volume.
Teat pipette – to use this place the teat pipette in the solution and squeeze the
top of the pipette to collect and measure. These have a fixed volume, it’s also
inexpensive and disposable. One limitation is that it’s not accurate for
measurement.
Small spatula – the use of this is to transfer solutes from one place to another.
This prevents the substance from making direct contact with you hand or skin.
However, one limitation is that it could spill while transferring substance. A way to
prevent this is keeping the containers in a proximity so that you are not traveling
far.
De-ionised water- used to dissolve the solute.
Filter funnel – this is used to pour and filter solutions into a flask, which in this
case would be a volumetric flask. A limitation is that some of the solution may be
3
Cole Parmer
https://www.coleparmer.com/blog/2018/08/10/use-volumetric-flask/
3
, left on the funnel. However, a way to overcome this is by rinsing the funnel with
water to get all the excess off it.
Calibration sheet
The values4 for calibrating a balance is that it helps to give accurate measurements
when weighing substances.
In the laboratory you may be conducting an experiment that requires accurate
measurements, so calibrating will be crucial in this matter.
If you do not calibrate your balance regularly, overtime it becomes unreliable as it may
produce inaccurate measurements which could affect your experiment.
Some advantages of calibrating are:
Maintains precise measurements.
Saves money- by not having to buy a new balance.
Maintenance a good efficiency
Reduces error
Calibration of a balance
Here are instructions on how to calibrate a balance, we should calibrate the balance
regularly using standard weights to ensure our measurements are precise which is
important when conducting an experiment in the laboratory.
Equipment
Top pan balance- to calibrate and weigh.
Tweezers- to pick up standard weights.
Cloth if needed to wipe scale.
Standard weights – to place on balance and weigh.
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