Qualitative and Quantitative Analysis
In qualitative research you look at the quality of a substance. At how it looks compared to other cases. You do an in-depth analysis of a specific case, and then make an informed decision about similar cases. For example, a qualitative study of the study habits ...
Qualitative analysis
In qualitative research you look at the quality of a substance. At how it looks compared to other cases. You do an in-depth analysis of a specific case, and then make an informed decision about similar cases.
For example, a qualitative study of the study habits of university students could include only a few people, or over twenty. Each person would be asked in-depth questions about how they study, and what works for them, and a general, informed assertion can then be made about these study habits.
Quantitative Analysis
In quantitative research you look at specific numbers. You study a large group (data sample) and do statistical analyses of the group, with experimental controls, manipulation of variables, and the modelling and analysis of your data.
For example, a quantitative study of those same study habits of university students would include a large number of people, for statistical relevance. The questions asked would include raw data of actual studying hours, and the most productive study times. These data points would then be analysed using graphical models.
Experiment: Boiling Points and Rate of Evaporation Part 2
This is the second part of the boiling points and rate of evaporation experiment in the lesson on Performing Experiments.
Results
Now that you remember how to plot graphs, go back to the data you obtained during the previous experiment.
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On the same set of axes, plot a graph of the volume (ml) versus the time (min) for each substance.
Analysis of results or discussion
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Analyse the results plotted on the graphs and the table.
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Which substance has the fastest decrease in volume? Which has the slowest decrease?
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Discuss if there are any relationships between your independent (time) and dependent (volume) variables (what type of graph did you plot?).
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It is important to look for patterns/trends in your graphs or tables and describe these clearly in words.
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Compare the different graphs and the different rates of evaporation to the boiling points of the substances.
Evaluation of results
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This is where you answer the question Is the rate of evaporation of a substance related to its boiling point?
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You need to carefully consider the results:
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Were there any unusual results? If so then these should be discussed and possible reasons given for them.
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Discuss how you ensured the validity and reliability of the investigation. Was it a fair test (validity) and if the experiment were to be repeated would the results obtained be similar (reliability)? The best way to ensure reliability is to repeat the experiment several times and obtain an average.
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Discuss any experimental errors that may have occurred during the experiment. These can include errors in the methods and apparatus. Make suggestions on what could be done differently next time.
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Did this experiment yield qualitative or quantitative results?
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Help
Results
You should record their results in a table like the one given. You should then plot a graph of all four liquids on the same set of axes. An example of how the drop in nail polish remover might look is given below.
Discussion and conclusion
You should find that water takes the longest time to evaporate and so has the shallowest drop on their graph. Water has strong intermolecular forces (hydrogen bonds). Ethanol (\(\text{CH}_{3}\text{CH}_{2}\text{OH}\)) and methylated spirits (mainly ethanol (\(\text{CH}_{3}\text{CH}_{2}\text{OH}\)) with some methanol (\(\text{CH}_{3}\text{OH}\))) both have hydrogen bonds but these are slightly weaker than the hydrogen bonds in water. Nail polish remover (acetone (\(\text{CH}_{3}\text{COCH}_{3}\))) has dipole-dipole forces only and so evaporates quickly and will have the sharpest decrease on their graph.
The graph should be exponential and as time increases the dependent variable (volume) decreases.
This lesson is part of:
Skills for Science