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Flashcards · J248 · Topic 1
Topic C1 – Particles flashcards
18 cards on Topic 1, subtopics C1.1 to C1.2. Pick a subtopic or study them all.
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C1.1 The Particle Model
- Particle model
- Everything is built from tiny particles, which may be atoms, molecules or ions. Their arrangement, movement and spacing explain the states of matter.
- Particles in a solid, a liquid and a gas: arrangement and movement
- Solid: regular, touching, vibrate in place. Liquid: random, close (mostly touching), slide past each other. Gas: random, far apart, move fast in all directions. The gaps between gas particles are empty space.
- Which changes of state take in energy, and which give it out?
- Taken in: melting, boiling or evaporating, subliming. Given out: freezing, condensing. Mass stays the same, because no particles are gained or lost.
- Physical change
- The particles stay the same. No new substance forms.
- Chemical change
- Atoms are rearranged into new particles. At least one new substance forms.
- Is "it can be reversed" enough to call a change physical?
- No. Some chemical changes can be reversed. The test is whether new particles, and so new substances, form.
- A substance has mp 6 °C and bp 81 °C. What state is it in at 2 °C, 25 °C and 95 °C?
- Below the mp: solid at 2 °C. Between mp and bp: liquid at 25 °C. Above the bp: gas at 95 °C.
- What does the inelastic sphere model of particles not take into account?Higher
- The forces of attraction between particles, the size of the particles, and the space between them (gases are drawn far too crowded).
- A gas takes up 1000 times the volume of the same mass of liquid. How much further apart are its particles?Higher
- About the cube root: ∛1000 = 10 times further apart.
C1.2 Atomic Structure
- Thomson's model of the atom
- Plum pudding: electrons embedded in positive charge.
- Rutherford's model of the atom
- Nuclear model: a small, dense, positive nucleus, with the atom mostly empty space.
- Bohr's contribution to the model of the atom
- Electrons in fixed shells at set distances from the nucleus.
- Chadwick's contribution to the model of the atom
- Discovery of the neutron.
- Alpha scattering: three observations and the conclusion from each
- Most passed straight through → the atom is mostly empty space. Some were deflected → the nucleus is positively charged. A very few bounced back → the nucleus is very small but contains most of the mass.
- Relative mass, charge and location of protons, neutrons and electrons
- Proton: mass 1, charge +1, nucleus. Neutron: mass 1, charge 0, nucleus. Electron: very small mass, charge −1, shells.
- Isotopes, and why they react identically
- Atoms with the same number of protons but different numbers of neutrons. Chemical behaviour depends on the electrons, which are the same.
- Protons, neutrons and electrons in a sodium-23 atom (atomic number 11)
- 11 protons, 23 − 11 = 12 neutrons, 11 electrons.
- Typical radius of an atom
- About 10⁻¹⁰ m (0.1 nm).