Practical 1: Experimental Design Wednesday 18 th March 2020 65410 - - PowerPoint PPT Presentation

Practical 1: Experimental Design

Wednesday 18th March 2020 65410 Skills for the Professional Chemist

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Lab demonstrators

[insert emails and names]

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Experimental Variables

• Variables are all the quantities that could change in an experiment
• There are different types of variables:

Independent variable Dependent variable Controlled variable

The condition that the scientist changes in the experiment The variable that you measure or observe The variable that does not change in an experiment

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Types of variables: Example

• Magnesium ribbon + dilute acid  hydrogen gas
• An experiment designed to measure the effect of magnesium ribbon

length on the volume of hydrogen gas produced

Independent variable Dependent variable Controlled variable

Magnesium ribbon length Volume of hydrogen gas Volume of HCl solution, Concentration of HCl solution

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Aims of this Practical

• To design and carry out experimentation to fulfil the brief given for

your appointed role, and report your findings in an objective manner

• To develop an understanding of the ideas behind experimental

design and measurement, and perform a valid experiment with consideration to the different types of variables

• To discuss and develop understanding of the use of mean values,

ranges, standard deviations and standard errors in reporting experimental findings

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Roles you will be assigned today

• Pairs of students will be assigned a role by your demonstrator
• This practical will explore experimentation using paper towels from

three different perspectives;

1. A research and development (R&D) chemist employed by Company C 2. A quality control (QC) chemist employed by Company A 3. A quality control (QC) chemist employed by Company B

• The brief for each role is given in the Practical Guide on UTSOnline

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Role 1: R&D Chemist (Company C)

Brief You are employed as an R&D Chemist in Company C (a new company) and have been asked to assist in designing a new paper towel (Paper towel C) that has greater absorbency and strength than other brands from Company A (Paper towel A) and Company B (Paper towel B). Aim To investigate the absorbency and strength of other paper towel brands and suggest ways the new product (Paper towel C) could be improved from the existing brands.

C

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Role 2: QC Chemist (Company A)

Brief You are employed as a QC Chemist in Company A and have been asked to provide information on whether claims that your paper towel (Paper towel A) does in fact soak up 2x more liquid than the rival company’s (Company B’s) product, Paper towel B. Aim To investigate the greater absorbency of Paper towel A compared to Paper towel B.

A

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Role 3: QC Chemist (Company B)

Brief You are employed as a QC Chemist in Company B, and have been asked to provide information on whether claims that your paper towel (Paper towel B) is in fact at least 2x stronger when wet than the rival company’s (Company A’s) product, Paper towel A. Aim To investigate the greater strength of Paper towel B compared to Paper towel A.

B

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Available equipment

• Thermometer
• Stopwatch
• Measuring cylinders

(various sizes)

• Beakers (various sizes)
• Disposable pipettes
• Balances
• Funnels
• Paper towels (A and B)
• Weights
• Sticky tape

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Today’s Task

• Design an experiment (or series of experiments) that fulfils the brief:

– Consider the variables involved

• Are you controlling variables that you are not testing?

– Consider repeating the experiment

• How many repetitions do you need? Why?

– Consider (and document) sources of error

• Systematic and/or random

– Could the method be replicated from your notes?

• Think about what you will need to include in your report

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Laboratory Report 1

• You will write a report detailing your findings, recommendations and

conclusions (with respect to your brief) addressed to your employer.

• Your report will include:

– Title – Project objectives – Materials and methods – Results – Discussion – Conclusion – Appendices (scanned lab notes)

• Further information is in the Practical 1 guide on UTSOnline

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Laboratory Report 1 submission

• Your individual report will be submitted as ONE FILE and must

contain your scanned laboratory notes. – Convert report to pdf – Scan lab notes (as pdf) – Merge pdf files (using a website such as pdfmerge.com or Adobe Acrobat Pro DC) – Submit via the link in UTSOnline Due: Friday 3rd April by 11:59 pm