Unit 4 Assignment 3 Practical techniques

Task 1 (P4) You will need to complete the following experiments. You will need to hand in a portfolio of your results. Calibration of a pH meter and the testing of the pH of several substances Investigate the conductivity of a dissolved solid in water. Calculation of the concentration of copper sulphate solution using colorimetry Determination of the resistance of a wire

Calibration of a pH meter and the testing of the pH of several substances In this practical you will need to calibrate a pH meter, your write up should describe the process that you went through to achieve this. Once you have calibrated the pH meter you will need to use it to test the pH of the substances provided. For each one you will need to take an appropriate number of results to ensure that the results you obtain are accurate.

What you should hand in: Title Aim Equipment list Labelled diagram Method Risk assessment Results table Research pages from the text book: 109

Investigate the conductivity of a dissolved solid in water. Ionic products will conduct electricity in a process called electrolysis. You will investigate this process and see what effect the amount of solid dissolved in the water has on the conductivity of the solution. For the practical you will need to set up the equipment as shown below: You will need to keep the power supply at the same voltage and measure the current in the circuit. You will test 4 solutions each with a different amount of solid added each time. You will need to record your results in an appropriate table, and repeat the tests to obtain an accurate set of results. In your write up you should include a diagram of the equipment that you used as well as a short conclusion from your experiment.

What you should hand in: Title Aim Equipment Diagram Method Risk assessment Results (table and graph) Conclusion Research from the book: page 114

Calculation of the concentration of copper sulphate solution using colorimetry You will need to use colorimetry to calculate the concentration of an unknown sample of copper sulphate. Firstly you will need to decide on the most appropriate filter to use for your results, if you do any test to decide this you should include these results in your write-up. Once you have selected the filter you will need to test several samples of a known concentration and draw a calibration curve. You will then test the sample with an unknown concentration and use your calibration curve to determine the concentration. Your write up should include any relevant results and graphs as well as your calculation of the concentration of the unknown solution.

What you should hand in: Title Aim Equipment list Diagram Method Risk assessment Results (table and graph) Conclusion Research from book: page 549

Determination of the resistance of a wire Determination of the resistance of a wire – You will need to use a practical method to investigate how the resistance of a wire changes with its length. To do this you will need to take several measurements of the same wire but at different lengths. You will need to choose the range and interval of your measurements to ensure that you get enough results to formulate a conclusion. You will also need to repeat the results to obtain an accurate set of results. The circuit for testing the resistance of the wire is shown on the next slide:

What you should hand in: Title Aim Equipment Diagram Risk assessment Method Results (table and graph) Conclusion Research in book: page

Task 2 (M3) For the equipment that you have used in your experiments explain the function of each type of instrument/sensor and justify why each one was a suitable choice for the experiment. See next slide for further help

Merit help – structure your work using the information below Introduction: why instruments and sensors in general are useful for scientific investigations List all the instruments (not all equipment!) used in your practical investigation work. Ammeter Voltmeter Colorimeter pH meter For each one, make a sub-heading and research what it is, what it measures and how it measures it (you will need a bibliography for this work). You may need to describe what things like current, voltage, concentration and pH is, in detail for each piece of equipment. You can then JUSTIFY the use of each piece of equipment by explaining how this was useful for your investigation.

Distinction help Task 3 (D3) For at least two of the experiments you have completed provide details of the evaluation of accuracy of the procedure used, comparing it to an alternative method of measurement. How to set it out: Choose 1 practical that you have completed for unit 4 and write the method in as much detail as possible. Make a subheading for ‘Details of the accuracy of the procedure’. Bullet point how you ensured accurate measurements. Subheading – Comparison to an alternative measurement – look up another method for your practical, write down the procedures needed to carry out the investigation and how it works. What are it’s positive and negative points? Write a final conclusion summing up which method is more accurate.