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8.9Chapter 8: Pure Substances and Solutions

Investigating temperature and solubility — Alhussan Chemistry - Stage 8 Revision Notes & Topical Questions

5 min read 9 parts Lesson 9 of 10 1 quiz

📚 Alhussan Chemistry - Stage 8 Hub / Topical Revision
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Lesson summary

8.9 Investigating temperature and solubility — Writing Up an Investigation — Alhussan International Academy — Chemistry (Stages 7–9) notes: Present evidence, write conclusions and evaluate an investigation of how temperature affects solubility.Observations — jottings such as "at …

  • Results table
  • Anomalous result
  • Line graph
  • Basic conclusion
  • Detailed conclusion
  • Explanation

Section 1 of 9Recording data

Observations
  • Observations jottings such as "at 0 °C, 7 g dissolved" are organised into a table to make patterns easier to spot and a graph easier to draw.
Results table
  • Results table write the independent variable in the left column and the dependent variable (mass dissolved, g) in the right column.
    • (water temperature, °C)
  • Include units in the column headings.
Repeats
  • Repeats record repeated trials where possible and calculate means.

Section 2 of 9Analysing the evidence

Pattern
  • Pattern as temperature increases, so does the mass of sodium carbonate that dissolves, so the prediction was correct.
Anomalous result
Anomalous result a result that does not fit the pattern.
  • In Hani's data the result at 10 °C was anomalous because the water was hotter than 10 °C when the reading was taken.
  • State whether an anomalous result was included, and ignore it when drawing the line of best fit.

Section 3 of 9Bar chart or line graph

Bar chart
  • Bar chart draw one when the independent variable is categoric or discrete.
  • Categoric variables are described by words.
  • Discrete variables are numbers with no in-between values.
Line graph
  • Line graph draw one when both variables are continuous.
  • A continuous variable can have any numerical value.

Section 4 of 9Drawing a line graph

1
Label the x-axis with the name and units of the independent variable.
2
Label the y-axis with the name and units of the dependent variable.
3
Choose a scale for each axis that uses most of the grid.
4
Write evenly spaced values on the lines of each axis.
5
Plot the points accurately.
6
Draw a line of best fit to show the pattern, which can be a straight line or a smooth curve, ignoring anomalous results.
  • Graph use
    • the graph can be used to predict values between the plotted points, such as the solubility at 35 °C.

Section 5 of 9Writing a conclusion

Basic conclusion
  • Basic conclusion the solubility of sodium carbonate increases with temperature, and the prediction was correct.
Detailed conclusion
  • Detailed conclusion include figures, for example solubility increases steadily from about 7 g/100 g of water at 0 °C to about 50 g/100 g at 50 °C.
Explanation
  • Explanation if a reason for the pattern is known, include it, for example that particles have more energy at higher temperatures and break up the solid more effectively.
Link to the aim
  • Link to the aim the conclusion answers the aim using the evidence and says whether the prediction or hypothesis was supported.

Section 6 of 9Evaluating the investigation

Limitation
  • Hani did not find the solubility at temperatures above 50 °C.
Improvements
  • Improvements increase the range by taking readings at 60 °C and 70 °C.
  • Repeat the anomalous reading at 10 °C.
  • Repeat all readings to make the results more reliable.
Quality of data
  • Quality of data comment on whether repeats were close together, whether there were anomalies and whether the method was fair.
Other limitations
  • Other limitations judging when the solid has just stopped dissolving is subjective, and the temperature falls as the mixture cools in the air.
  • Use a water bath, smaller steps of solute and more temperatures.
Further work
  • Further work test another solute.

Section 7 of 9Report structure and wording

Report structure and wording
Order of a report
  • Order of a report aim, hypothesis, variables, apparatus and method, results, analysis, conclusion and evaluation.
Hypothesis
Hypothesis a testable prediction with a scientific reason.
Method wording
  • Method wording use the passive voice and past tense.
Key words
  • Key words reliable means similar results when repeated, accurate means close to the true value, and precise means finely measured.

Section 8 of 9Key terms

TermMeaning
Hypothesisa testable prediction with a reason.
Variablea factor that can change.
Anomalous resulta result that does not fit the pattern.
Evaluationa judgement of the quality of a method and results.
Reliablegiving similar results when repeated.
Continuous variablea variable that can have any numerical value.

Section 9 of 9Exam technique

1
Writing a conclusion that does not refer to the data — quote figures from the results.
2
Plotting the dependent variable on the x-axis — the independent variable goes on the x-axis.
3
Joining the points of a smooth trend with a ruler — draw a line of best fit.
4
Confusing reliability with accuracy — reliable means repeatable and accurate means close to the true value.

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