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20 October 2014
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Royal Institution Christmas Lectures 2010

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Royal Institution Christmas Lectures: melting chocolate experiment

Why chocolate melts and jet planes don’t

As we zoom into the microscopically small realm beneath our fingertips to explore the tiny world we have created inside mobile phones, jet planes and chocolate, curious things start to happen. Gravity becomes less and less important, while stickiness and quantum mechanics start to dominate.

This is the wild west of science, where anything and everything seems possible, but is it? Can we create invisibility cloaks, self-healing phones and super-strong jet planes just by controlling the scale of things?

Journey into the inner space of the things around us to find out how the very small affects the very large. Mark shows that even the taste of chocolate depends on the size of extraordinary crystals which are designed to only melt in your mouth.

Lesson 4: Surface area and fireworks

Suitable for: 14–16

Curriculum and learning links: Rates of reaction, alkali metals and flame tests

Learning objectives:

  • Describe how to perform a flame test to identify metal ions in mystery compounds.
  • Explain why powders react more quickly than lumps using ideas about collisions between particles.

Lesson 5: How strong is Velcro?

Suitable for: 11–16

Curriculum and learning links: Forces and gravity, mass and weight, designer polymers

Learning objectives:

  • Explain how Velcro works.
  • Investigate the relationship between area of Velcro and mass needed to pull it apart.

Lesson 6: Smart phones and car safety

Suitable for: 14–16

Curriculum and learning links: Forces and gravity, energy transfers, car safety features

Learning objectives:

  • Know how accelerometers are used in smart phones and car safety features.
  • Understand why airbags, seatbelts and crumple zones help to prevent injuries.
  • Investigate the relationship between collision time and force of impact.

Lesson 7: Invisibility cloaks

Suitable for: 11–14

Curriculum and learning links: Refraction of light

Learning objectives:

  • Describe how light changes direction at the boundary between two different substances.
  • Explain why this happens.

Lesson 8: Crystals and chocolate

Suitable for: 11–16

Curriculum and learning links: Cooking chemistry, composite materials, changes of state, latent heat

Learning objectives:

  • Describe melting and freezing as endothermic and exothermic respectively.
  • Describe the structure of chocolate as a composite matrix of crystals arranged in cocoa butter.
  • Explain how the microstructure of a material (in this case cocoa butter) can affect its properties.

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