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The Factors which Affect Radiation in Small and Large Beakers.

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Introduction

Bilal Ali          Human Physiology and Health          March 2003

Human Physiology and Health Coursework –

The Factors which Affect Radiation in Small and Large Beakers

          By Bilal Ali

THE FACTORS THAT AFFECT RADIATION OF HEAT THROUGH WATER IN DIFFERENT SIZE BEAKERS

AIM

        My aim in this investigation is to investigate the factors that affect radiation (heat loss) of heat of water in different size beakers. Therefore, my aim is to find out how different surface area and volume ratios in organisms lead to variations in heat loss  (and factors which affect it).

INTRODUCTION

Large animals have the ability to retain heat more easily than smaller animals because they have a larger surface area to volume ratio. This is what I am trying to prove in the experiment. There are examples of this in nature. In winter the robin fluffs its wings up in order to retain more heat. When it does this, it forms a more spherical shape and this also gives better heat retention. But as I am unable to use live animals in the experiment I am using beakers full of hot water. The reason that an animal with a lower surface area to volume ratio retains heat more efficiently is because there is a greater volume to keep the heat and a smaller surface area that is open to outside elements.

        In order to reach this objective, I will carry out a number of experiments using a safe and practical procedure. I will carry out four experiments.

...read more.

Middle

Land & sea breezes are due to convection. Atmospheric winds. Hot water systems.

RADIATION

The big difference between radiation and convention and conduction is that radiation does not need a medium to travel through; therefore radiation can happen through a vacuum.  Radiation takes place by the transmission of electromagnetic waves (EM waves) from a hot object to any other object. If the rays from a hot object hit another object then some of the rays are reflected and some of the rays are absorbed therefore causing a rise in temperature. The rate as which a body/surface radiates depends on its temperature and the actual nature of the surface. A black surface absorbs more heat than a white surface and therefore radiates more heat. The reason why a white surface radiates less heat is that a white surface reflects all heat and therefore does not retain as much heat hence the inability to radiate as much heat as a black surface.  

EXAMPLES OF RADIATION:

  • Heat from the Sun travels to other planets and the rest of the solar system via a vacuum by radiation.
  • Grills use radiation to give out heat and thereby cooking food.

VOLUME TO SURFACE AREA RELATIONSHIP

        An organism (or in this case a beaker) that has a large volume in comparison to its surface area (i.e. an elephant) will lose heat less quickly than an organism that has a smaller volume in comparison to its surface area (i.e. a mouse), therefore in theory an elephant loses less heat for its size than a mouse. This is because an organism that has a large surface area compared to its volume will lose heat quicker as it has more surface area to lose the heat and has less heat to lose.  This concept can be used in this investigation to predict and to explain why certain sized beakers lose heat more quickly than others.

PREDICTION

        With reference to my theory, I predict that the small beaker will lose heat via radiation the fastest and I also predict that largest beaker will lose heat the slowest. This is because the small beaker as a small volume to surface area ratio meaning it has more surface area to lose heat and it has less heat to lose hence greatest heat loss (through radiation). The large beaker, however, will lose heat (via radiation) at a slower rate because it a large surface area to volume ratio meaning it has a less surface area to lose heat and it has more heat to lose. I also predict that the beakers that have a insulation to reduce radiation will lose heat more slowly. More specifically, the beaker that will have a black insulation will lose heat more quickly than the beaker that will have a white insulation. This is because black surfaces absorb more heat and therefore radiate more heat and white surface reflect more heat hence radiate little heat.  

METHOD

  1. Firstly, I got all the apparatus that were needed.
  2. I placed some bubble wrap on the workbench and placed the beakers on top of it.
  3. I boiled the water in the kettle and then carefully poured it in the beaker to the right amount that was needed for the experiment.
  4. Foil was then used to cover the top of the beaker. Using a scalpel a small hole was cut for the thermometer to be placed in the beaker.
  5. An insulating material (wither white or black bag) was wrapped around the beaker to reduce radiation.
  6. The temperature started to drop and at a certain temperature (which would remain constant throughout each of the experiments) the stop clock was started.
  7. Each experiment lasted one hour and every 12 minutes for an hour the temperature readings were taken (therefore five readings in total).
  8. The same method was used for each of the other experiment.

APPARATUS

In this experiment the following apparatus were used:

  • Kettle – to boil the water
  • 2x 175ml beakers
  • 2x 125ml beakers
  • Thermometer – to measure the temperature of the water.
  • Foil – placed on top of beaker (as a lid) to stop convection.
  • Bubble Wrap – placed on the bottom of the beaker to stop conduction.
  • Stop clock – to measure the time for the experiment (and time to take readings at).  
  • Foil – used on top of the beaker (as lid) to stop convection.
  • Bubble Wrap – placed beneath beaker to strop conduction.
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Conclusion

TIME/ mins

TEMPERATURE/oC

0

78

20

63

40

54

60

47

I carried out the same the same experiments as my preliminairy experiment. I did this because it provided me with an adequate perception of the results that I was going to obtain from my actual experiment. Therefore, from this I had a sufficient concept on how to carry the experiment out more accurately. The results I gathered from my preliminary experiment are shown below:

EXPERIMENT                                                        CONTROL

TIME/ mins

TEMPERATURE/oC

0

82

20

58

40

48

60

41

In this experiment, a smaller time scale was used than in the main experiments. This is because I only wanted to test my prediction to see if it was right and to gain an insight into the results that were going to be gained.

        The results that as time went on the temperature of the water in the beakers of both experiments went down. The temperature of the control beaker decreased more significantly than the temperature in the experimental beaker. This is because the control did not have any cover to stop radiation.  The graph on the following page shows the trend more clearly. The graph shows that time and temperature (temperature loss) have an inverse relationship because as time increases the temperature decreases.

Modification of Preliminary Experiment to Main Experiment

When carrying out the preliminary experiment, there were some flaws in the experiment that were noticed. The main flaws (and the only ones) in the preliminary experiment was that the volume of water in the experimental beaker and the control beaker were different. The initial temperature of the experimental beaker and control were different. The other fault in the preliminary experiment was that both experiments were started at different times.

In order to gain sufficient and consistent results these flaws in the preliminary experiments were rectified in the main experiment.  

...read more.

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