Investigate how the material of a cup affects the time it takes for the liquid to cool down.

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                Which coffee stays the hottest?

Aim:

To investigate how the material of a cup affects the time it takes for the liquid to cool down.

Prediction:

The factors that will affect this investigation are:

  • The Material  of the cup
  • Colour of the cup
  • Surface area
  • Amount of water the cup contains
  • Whether its got a lid or not
  • Room temperature (temperature of its surroundings)
  • Thickness of cup
  • Type of liquid it contains
  • Air movement surrounding the cup.

I will be investigating what effect the material of the cup has on the rate at which the watercools down.

I predict that the polystyrene cup would keep the water hotter for longer, the paper cup would be the second, the ceramic would come third and the water in the metal cup would cool down the quickest. This is because polystyrene is a better insulator than paper, paper is better than ceramic etc.                  

Reasons:

A material that prevents heat loss is called an insulator. Insulators have to prevent these three types of heat loss:

  • Conduction
  • Convection
  • Radiation

Conduction:

Conduction is the flow of heat through matter, from places of higher temperature, to places of lower temperature without movement of the matter as a whole. Conduction of heat occurs mainly in solids. This process is where vibrating particles pass their extra vibration energy to neighbouring particles.

Most metals are good conductors of heat, these are used whenever heat is required to travel quickly through something. Saucepans, boilers and radiators are made of metals such as aluminium, iron and copper.

 The inside of a motorbike engine is hot. The burning of the fuel provides a continuous supply of energy. Some of the energy pushes the pistons and turns the wheels. Some just pushes up the temperature. The engine would over heat if the energy could not flow safely away. It flows through the metal of the engine block, out into the air. Cooling fins provide large surface where the cool air and hot metal meet. They increase the rate of the engine flow. The metal must conduct the energy.

As one part of a metal gets hotter, its particles move with more energy. Its atoms vibrate more and more violently, and some of its electrons move more energetically. So the energy spreads through the metal, this process is called conduction.

Thermal conduction does not only happen in metals. In other solids energy moves from particle to particle, but much more slowly than in metals. Metals are good thermal conductors while most other substances are good thermal insulators.

All substances have electrons. However, it is only in metals that electrons can easily move from atom to atom. In other substances, electrons are trapped inside atoms. These trapped electrons cannot carry energy from atom to atom. This is the main reason why these substances conduct energy slowly.

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Materials such as wood, glass, cork, plastics and fabrics are bad conductors, the handles of some saucepans are made of wood or plastic. Cork is used for tablemats.

Metal objects below body temperature feel colder than those made of bad conductors because they carry heat away faster from the hand – even if all the objects are exactly the same temperatures.

Also in liquids like water, the forces between the particles are generally weaker than in solids. So particles do not push and pull each other so much – they simply have less to do with ...

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