Particles | OCR GCSE Combined Science Chemistry, Higher tier (J250)
Particles
- 68 questions
- 5 subtopics
- Paper 9 (Chemistry)
- Paper 9 (Chemistry)
Particles is examined in Paper 9 (Chemistry).
It covers the particle model and changes of state, limitations of the particle model, how the atomic model changed, and the structure of the atom, the size of atoms, and the subatomic particles and calculating protons, neutrons and electrons.
Sample questions from Particles
Answer each one closed book first, then open the answer.
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The particle model and changes of state
Name the change of state in which a liquid becomes a gas, and the reverse change.
Show the answer
A liquid becoming a gas is boiling or evaporating, and a gas becoming a liquid is condensing. -
The particle model and changes of state
Explain why burning magnesium in air is a chemical change.
Show the answer
The magnesium atoms join with oxygen atoms to form a new substance, magnesium oxide, which has different properties from the magnesium. -
Limitations of the particle model
Explain why leaving out the forces between particles makes the model poor at explaining boiling points.
Show the answer
Boiling requires enough energy to overcome the attraction between the particles, so a model with no forces cannot explain why different substances boil at different temperatures. -
Limitations of the particle model
Explain why real particles cannot be solid spheres.
Show the answer
An atom is mostly empty space, with a tiny nucleus and electrons in the space around it, so it is not solid throughout. -
How the atomic model changed, and the structure of the atom
Explain how Rutherford interpreted the results of the alpha scattering experiment.
Show the answer
He concluded that an atom is mostly empty space with its positive charge and nearly all its mass concentrated in a tiny nucleus at the centre. -
How the atomic model changed, and the structure of the atom
How does the radius of the nucleus compare with the radius of the whole atom?
Show the answer
The nucleus is very much smaller, with a radius of the order of ten thousand times less than that of the atom. -
The size of atoms, and the subatomic particles
Put a nucleus, a whole atom and a small molecule in order of increasing size.
Show the answer
The nucleus is smallest, then the atom, then the small molecule. -
The size of atoms, and the subatomic particles
Explain why the mass of the electrons is ignored when the mass of an atom is worked out.
Show the answer
An electron has a mass of about one two-thousandth that of a proton, so its contribution to the total is negligible.
The 5 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| The particle model and changes of state | What the particle model assumes, the arrangement and movement of particles in solids, liquids and gases, melting, freezing, boiling, condensing and sublimation, why melting needs energy and gases compress, what physical and chemical changes are and how to tell them apart, why melting, freezing and dissolving salt are physical while burning magnesium is chemical, and why physical changes reverse easily. | 17 |
| Limitations of the particle model | How the simple model pictures particles as solid spheres, the forces, size differences and spacing it leaves out, why real atoms are not solid, why it cannot explain condensing, and why it is still useful. | 8 |
| How the atomic model changed, and the structure of the atom | How the model of the atom developed from Dalton's solid sphere through Thomson's electron and plum pudding model, Geiger and Marsden's alpha scattering experiment and Rutherford's nucleus to Bohr's shells and Chadwick's neutron, why models change with new evidence, and the structure of the atom: its charged nucleus, its tiny size, where its mass lies, and why it is neutral and mostly empty space. | 16 |
| The size of atoms, and the subatomic particles | The typical radius of an atom and length of a bond, writing sizes in standard form, comparing a nucleus, an atom and a small molecule, the relative charges and masses of protons, neutrons and electrons, where each is found, why electron mass is ignored and atoms are neutral, and the symbols ~, <, >, << and >>. | 18 |
| Calculating protons, neutrons and electrons | What atomic number and mass number are, working out the number of neutrons, what isotopes and ions are, where the two numbers are written beside a symbol, and counting the protons, neutrons and electrons in an atom and in chloride and magnesium ions. | 9 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby topics
OCR GCSE Combined Science Chemistry, Higher tier Active Recall Guide
Every topic, not just this one. 916 questions with their answers.