Investigating Heat Loss in Model Animals

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Biology Coursework :

Investigating Heat Loss in Model Animals

PLANNING

Intentions

This experiment is being conducted to investigate the relationship between insulation (e.g. an animal’s fat and fur), and (body) temperature using water, test tubes and foam insulation.

Variables

There are various variables that need to be taken into account during the experiment:

                        Water volume;

                        External factors, e.g. room temperature, wind strength.

                        Type of insulation;

Number of layers of insulation;

Different test tube sizes, e.g.        Width;

                                Height;

                                Glass thickness;

(all affect surface area or insulation).

Scientific Background

We know that in the natural world, body temperature is a very important factor in the ability to survive.  This is demonstrated throughout the world in a variety of different climates.

For example, to survive the severe cold, animals in the Arctic generally have more body fat and thicker, longer fur than those of a hotter climate such as Africa.  This is a demonstration of Bergman's Rule, which states that animals tend to be larger in colder regions for reasons of thermoregulation.  The larger an animal is, the greater its volume, thus the lower its surface area to volume ratio and hence the lower its heat loss.

The two factors that most affect an animal’s body heat retention or loss are its volume to surface area ratio as mentioned above(the ratio of the volume of the animal compared to its surface area), and the amount of insulation it carries around with it.  This insulation is in the form of fat, feathers or fur (e.g. hairs in humans).  The extra bulk greatly reduces heat loss and can make the difference between survival and extinction.

Heat  works by slowing down the  at which energy moves from a warm thing to its cooler surroundings.  A good heat insulator will:

  • stop the flow of air which allows convection to happen
  • be made of a material which is a bad conductor of heat
  • reflect heat radiation back where it is wanted.

Heat loss is a result of energy transfer by heat where the moving molecules of one material increase the energy of the molecules in another.  This occurs in three different ways:

Conduction

Conduction is when heat energy is passed from one particle to another, close by particle. It is most effective if the particles are close together which is why most good conductors are solids.  Conduction is also improved if the molecules have free electrons, which is why metals are such good conductors.

Insulation reduces conduction because it is a bad conductor of heat itself, and it traps layers of still air.  Stationary air is a bad conductor of heat because air has particles that are spread out and have very few free electrons, meaning that heat can only travel through it very slowly.

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Convection

Convection is when heat is transferred in a liquid or gas due to the particles moving.  As the particles warm up, the spaces between them expand, making them less dense and thus making them rise.  The cooler particles are more dense and sink, replacing the warmer particles.  This is known as a convection current.

Insulation reduces convection because the air cannot pass through the layers to convect.

Radiation

Radiation is when a warm object emits infrared electromagnetic radiation, which can be absorbed by other objects, heating them up.  

Radiation is usually reduced by ...

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