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O-Level The Particulate Nature of Matter
kinetic particle theory and the structure of the atom
What the syllabus expects
- Outline the solid, liquid and gaseous states and account for changes between them using kinetic particle theory together with the energy changes involved.
- Present and account for evidence showing that particles move within liquids and gases.
Scope: Brownian motion is not examined. - Use particle ideas to explain common examples of diffusion, such as tea and coffee grains colouring water or scents and cooking aromas spreading.
- Describe qualitatively how molecular mass influences diffusion speed, and explain why the rate of diffusion depends on temperature.
- Give the approximate relative masses and the relative charges carried by a proton, a neutron and an electron.
- Using diagrams, set out how an atom is built, with nucleons (protons and neutrons) in the central nucleus surrounded by electrons occupying shells (energy levels).
Scope: Students are not expected to know the s, p, d or f sub-shell scheme; Papers 1 and 2 come with a Periodic Table. - Give definitions for proton (atomic) number and nucleon (mass) number.
- Read and apply nuclide notation, for example the carbon-12 form written as superscript 12 and subscript 6 before C.
- Define what isotopes are.
- Work out how many protons, neutrons and electrons are present in atoms and ions when the proton and nucleon numbers are provided.
How it's examined
Questions on this topic most often ask you to explain, name. About 11% of the past-paper style questions in Rae's bank for this subject sit in this topic.
Worked examples
Example 1 (2 marks)
Using the kinetic particle theory, explain why the temperature of the gases must be held constant during this experiment. [2]
Show the worked answer
By kinetic particle theory the temperature of a gas fixes the average kinetic energy (and hence average speed) of its particles. If the temperature were allowed to change, the particles' average speed would change, so they would strike the container walls with a different frequency and force, altering the pressure independently of the quantity actually being investigated. Holding the temperature constant keeps the average kinetic energy, and therefore the collision frequency and force, constant, so the measured relationship (e.g. pressure against volume) depends only on the variable being changed.
Example 2 (2 marks)
An ion of a copper isotope has the formula 65/29 Cu2+. Fill in the table with the details of this ion. sub-atomic particle | number in 65/29 Cu2+ electron | proton | neutron |
Show the worked answer
For 65/29 Cu2+: the lower number 29 is the proton (atomic) number and the upper number 65 is the nucleon (mass) number. Protons = 29. Electrons = 29 - 2 = 27 (the 2+ charge means two electrons have been lost). Neutrons = 65 - 29 = 36.
Example 3 (2 marks)
A sample of X is made up of three substances, A, B and C. During an experiment, a student accidentally let a drop of sample X fall into the solvent, and noticed that the colour of X gradually spread out through the solvent. Name this process and explain why it happens.
Show the worked answer
The coloured particles of X spread out through the solvent on their own. This process is diffusion. It happens because particles are in constant random motion; the particles of X move from a region of higher concentration (where the drop landed) to regions of lower concentration until they are evenly spread throughout the solvent.
More worked questions on this topic
- [Past-paper practical, O-level Chemistry, Paper 3] The water of crystallisation in anhydrous so (2 marks)
- Complete the table for the ions 39/19 K+ and 16/8 O2-, giving the number of protons, neutrons a (3 marks)
More O-Level Pure Chemistry topics
Experimental Chemistry · Chemical Bonding and Structure · Chemical Calculations · Acid-Base Chemistry · Qualitative Analysis · Redox Chemistry · all of O-Level Pure Chemistry