Starter quiz
- What happens to the particles in a liquid when its temperature increases?
- They expand to take up more space.
- They contract and take up less space.
- Their size does not change. ✓
- Their average speed increases. ✓
- Their average speed decreases.
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- What is the smallest component of an element?
- a gas
- a molecule
- an atom ✓
- a crystal
- a mole
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- Which of these are elements?
- gold (Au) ✓
- carbon dioxide (CO)
- oxygen (O) ✓
- hydrochloric acid (HSO)
- uranium (U) ✓
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- In which state are the particles in a substance most free to move around?
- solution
- solid
- liquid
- gas ✓
- crystal
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- Match the particles to their descriptions.
- electron⇔negatively charged particle found outside a nucleus ✓
- proton⇔positively charges particle found in a nucleus ✓
- neutron⇔particle with no charge found in a nucleus ✓
- atom⇔neutral particle ✓
- Starting with the largest, put these objects in order of mass.
- 1⇔a 1 kg block of gold
- 2⇔a gold ring
- 3⇔a single gold atom
- 4⇔a single proton
- 5⇔a single electron
Exit quiz
- Match each of the following terms used in nuclear physics to the correct definitions.
- background radiation⇔the radiation in the surroundings at a particular place ✓
- alpha particle⇔a positively charged particle that is a type of radiation ✓
- alpha scattering experiment⇔an investigation to explore the structure of atoms ✓
- nucleus⇔the part in the middle of an atom which contains most of its mass ✓
- Which of the following are properties of an alpha particle?
- It has positive electrical charge. ✓
- It has negative electrical charge.
- It is uncharged (neutral).
- It is a particle with a mass similar to a helium atom. ✓
- It is high frequency electromagnetic radiation.
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- Which of the following are classified as artificial sources of background radiation?
- rocks
- nuclear fallout from weapons tests ✓
- cosmic rays
- brazil nuts
- nuclear waste from power stations ✓
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- Match the results of the alpha particle scattering experiment (where a beam of alpha particles is fired at gold foil) to the corresponding conclusions made.
- most pass straight through⇔most of an atom is empty space ✓
- some are deflected by large angles⇔there is a nucleus with a positive charge ✓
- a small number ‘bounce back’⇔the nucleus contains most of the mass of the atom ✓
- Starting with the earliest, sort the following into date order.
- 1⇔model of atoms as small, solid spheres
- 2⇔discovery of the electron and use of ‘plum pudding’ atomic model (Thomson)
- 3⇔discovery of the nucleus using alpha particle scattering experiment (Rutherford)
- 4⇔electron shell model developed (Bohr)
- 5⇔discovery of neutrons in nucleus (Chadwick)
- Henri Becquerel discovered radiation in 1896 when investigating uranium salts. What properties did the radiation have that lead to the discovery?
- It was an artificial substance.
- It could pass through paper. ✓
- It caused objects to glow in the dark.
- Exposed photographic film was made darker. ✓
- It made him ill.
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Worksheet
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Lesson Details
Key learning points
- Background radiation is caused by unstable nuclei that are around us all of the time.
- Atoms are very small with a radius of about 1 × 10⁻¹⁰ m.
- The alpha particle scattering experiment (Rutherford, 1909) provides evidence for the size and nature of atomic nuclei.
- An atomic nucleus has a radius about 10 000 times smaller than that of an atom.
- Most of the mass of an atom is in its nucleus.
Common misconception
Atoms are visible under powerful optical microscopes.
Emphasise that atoms are far too small to see and our descriptions of atoms are models, based on evidence, that help us understand how they behave.
Keywords
Background radiation - the radiation in the surroundings of a particular place
Alpha particle - a small, positively charged particle which was used to discover the nucleus
Alpha scattering experiment - the experiment used to discover the atomic nucleus from the deflection of alpha particles fired at it
Nucleus - the central part of an atom which contains most of the mass and all of the positive charge
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