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11.3Unit 8: Chemical reactions

Investigating acids and alkalis — Cambridge Checkpoint Science 0893 Revision Notes & Topical Questions

5 min read 7 parts Lesson 3 of 4 1 quiz

📚 Cambridge Checkpoint Science 0893 Hub / Topical Revision
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Lesson summary

11.3 Investigating acids and alkalis — CHECKPOINT (CHEMISTRY) notes: Word a testable question and plan a fair investigation into acids and alkalis.Precise question — "Which is the best remedy?" is not precise, because best could mean cheapest, tastiest or most effectiveTestable v…

  • Testable version
  • Equipment and safety
  • Independent variable
  • Control variables
  • Anomalous result
  • Model — use a beaker of acid, not stomach acid

Section 1 of 7Asking testable questions

Precise question
  • "Which is the best remedy?" is not precise, because best could mean cheapest, tastiest or most effective
Testable version
  • "Which indigestion powder neutralises the acid using the least amount of powder?"

Section 2 of 7Planning an investigation

Model
  • Model use a beaker of acid, not stomach acid
Fair test
  • Fair test change one variable and keep the others the same
Equipment and safety
  • Equipment and safety decide what equipment is needed and how to stay safe
Recording
  • Recording decide how to record the results

Section 3 of 7Variables

Variable
Variable something that can change in an investigation
Independent variable
Independent variable the variable you change (the type of powder)
Dependent variable
Dependent variable the variable you measure (the number of spatulas needed)
Control variables
Control variables the variables kept the same, such as acid volume, concentration and indicator

Section 4 of 7Measuring neutralisation

1
Put the same volume of hydrochloric acid, pH 1, in each beaker.
2
Add a few drops of universal indicator.
3
Add one powder spatula by spatula until the indicator is green.
4
Record the number of spatulas used.

Section 5 of 7Reliable results

Repeats
  • Repeats repeat the investigation and calculate a mean
Anomalous result
  • Anomalous result a result that does not fit the pattern; find the cause and leave it out of the mean
Evidence
  • Evidence more than one set of results gives stronger evidence for a conclusion

Section 6 of 7Key terms

TermMeaning
VariableA factor that can change in an investigation.
Independent variableThe variable that is changed.
Dependent variableThe variable that is measured.
Control variableA variable kept the same.
Anomalous resultA result that does not fit the pattern.
MeanThe average of repeated results.

Section 7 of 7Exam technique

1
Changing more than one variable at once.
2
Including an anomalous result in the mean.
3
Using a question that cannot be tested.
4
Basing a conclusion on one set of results only.

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