7.2Reactivity 3 — What are the mechanisms of chemical change?

Tool 2: Technology — IB Chemistry SL Revision Notes & Topical Questions

5 min read 10 parts Lesson 6 of 12 Unit quiz

📚 IB Chemistry SL Hub / Topical Revision

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Lesson summary

7.2 Tool 2: Technology — IB SL Notes — IB CHEMISTRY SL notes: Use data loggers, sensors, databases, models, simulations and spreadsheets to collect and process data in chemistry.Computational chemistry — uses computer simulations and mathematics to study chemicals and how they re…

Sources of large data sets
Processing
Measurements
Advantages
Definition
Temperature probe

Part 1 of 8Computational chemistry and data

Computational chemistry and data

Computational chemistry

Computational chemistry uses computer simulations and mathematics to study chemicals and how they react.

Purpose

Purpose it helps scientists spot trends and make predictions, such as reactivity or properties of substances.

Sources of large data sets

Sources of large data sets experiments, sensors, existing databases, and computer models and simulations.

Part 2 of 8Data loggers

1Function

Function a data logger collects data quickly and accurately and stores it in a computer, often as a table.

2Processing

Processing the computer can calculate averages, draw graphs and find gradients more precisely than a person.
- (rates of change)

3Measurements

Measurements temperature, pressure, pH or conductivity through connected sensors.

4Display

Display results appear on a screen in real time.

5Advantages

Advantages many readings in a short time, less human reaction-time and parallax error, and several variables logged at once.

Part 3 of 8Sensors

Definition

Definition an input device that detects a specific change in its surroundings and converts it into an electrical signal stored by the data logger.

Benefit

Benefit lets chemists collect large data sets in a short time.

Temperature probe

Temperature probe replaces a thermometer in calorimetry and monitors exothermic and endothermic reactions.

Pressure sensor

Pressure sensor measures gas or liquid pressure, in gas law experiments or reactions that change pressure.

Conductivity sensor

Conductivity sensor relates conductivity to ion concentration, studies electrolytes and follows reaction rate when ions are made or used.

Part 4 of 8pH meters

Construction

Construction a reference electrode that gives a constant reading and a glass-membrane electrode that responds to H⁺ ions.

Operation

Operation the meter compares the two electrodes and displays the pH.

Uses

Uses finding the end point of acid-base titrations, studying acids, bases and salts, and testing how well buffers resist pH change.

Calibration

Calibration a pH meter is calibrated with buffer solutions before use.

Part 5 of 8Databases

Databases

Definition

Definition a structured collection of data that can be searched, sorted, filtered and analysed quickly.

Types of data

Types of data formulae of polyatomic ions, melting and boiling points, enthalpies, entropies and Gibbs energies, rate constants, equilibrium constants, NMR and IR spectra, structures, bond lengths and organic synthesis conditions.

Database	Content
Spectral Database for Organic Compounds	Formula, mass, structure and ¹³C NMR, ¹H NMR and IR spectra
MolCalc	3D molecules with enthalpy, heat capacity, entropy, vibrational frequencies, orbitals and polarity
PubChem	Structures, names, chemical and physical properties of a very large number of chemicals
ChemSpider	Chemical properties and spectra
NIST WebBook	Formulae, properties and reaction searches

Part 6 of 8Models and simulations

Model

Model a simplified version of reality, such as the ball-and-stick model of bonds and angles.

Approximation

Approximation every model involves some simplification and loss of accuracy, however powerful.

Simulation

Simulation uses models based on chemical principles to predict the behaviour of atoms, molecules and systems.

Value

Value explores scenarios that are unsafe or impractical,
- such as the violent reactions of heavy Group 1 metals with water, predicted from lighter ones.

Variable control

Variable control users alter variables, e.g. temperature, pressure and volume of a gas, and collect data from the predictions.

Reliability

Reliability depends on the quality of the models and assumptions.

Online resources

PhET has simulations of molecular shapes, the pH scale and states of matter.

Part 7 of 8Processing data with spreadsheets and graphs

Organisation

Organisation enter raw data and arrange it by parameter in rows and columns.

Manipulation

Manipulation perform calculations, statistics and mathematical operations on data sets.

Visualisation

Visualisation built-in functions produce graphs that reveal trends,
- such as first ionisation energy against atomic number or pH against volume of acid.

Graph types

Graph types line graphs and scatter plots show trends and correlations, while bar graphs and pie charts compare data.

Direct recording

Direct recording output from a digital pH probe can be fed straight into a spreadsheet to plot a graph.

Calibration curve

Calibration curve a line graph of absorbance against known concentrations lets the concentration of an unknown be read from its absorbance.

Part 8 of 8Modelling and visualisation tools

1Computational models

Computational models give insight into complex processes while saving time and resources compared with experiments alone.

2Molview

Molview free software that builds structures and shows them in 3D.

3Visualisation

Visualisation interactive 3D tools help in exploring structures and behaviour.

4Reaction pathways

Reaction pathways graphs of pathways and kinetic data help elucidate mechanisms.

5Use in assessment

Use in assessment look for chances to use spreadsheets, graphs and modelling in practical work.

Key terms

Term	Meaning
Data logger	A device that records and stores data from sensors, usually on a computer.
Sensor	An input device that converts a physical or chemical change into an electrical signal.
Database	A structured collection of data that can be searched and analysed.
Model	A simplified version of reality used to explain or predict behaviour.
Simulation	A model-based prediction of how a system behaves when variables are changed.
Calibration curve	A graph of absorbance against known concentrations.

Avoid these mistakes

Treating a simulation as exact — all models simplify reality.

Using an uncalibrated pH meter — calibrate with buffers first.

Assuming a data logger removes all error — sensor calibration and response time still matter.

Using a graph type that hides the trend — choose line or scatter graphs for relationships.

Last updated: 12 October 2026