Class Results
My results show a clear correlation between temperature increase and
the height achieved when bounced. So this means that heating the ball does give it more energy than it originally had. The sort of energy must be kinetic energy, in the molecules of the rubber and air. Heat energy is also present.
Intermolecular forces of attraction hold solid matter together. These
forces can be described to be like springs holding the elastic
material together. When a squash ball hits a surface these springs are
compressed and stretched. The stretching and compressing of the
springs stores the kinetic energy (k.e.) of the ball as potential elastic
energy (p.e.e). When all the kinetic energy has been stored the spring
will release the p.e.e. back into k.e. by returning to their original
shape. Some of the kinetic energy is lost during this transition and
it becomes heat energy (warming up the springs). So the ball doesn’t
bounce back to its original height.
The higher the temperature of the rubber the greater the vibration of the springs and if the temperature becomes hot enough the material melts or leaves as a gas and the springs are broken and the material is no longer elastic but becomes a fluid or gas. Also many elastic materials such as rubber become very brittle at extremely cold temperatures and loose their elasticity and will shatter like glass if they are dropped. This means that the behaviour of the springs holding the matter together is strongly affected by temperature.
Matter in a gas is not held together by intermolecular forces of
attraction but is the opposite. The molecules are whizzing about at
speed, because they have so much energy that they have broken the
intermolecular forces of attraction. In gases the hotter they are the
more kinetic energy they have in the form of the molecules moving with
more speed.
When a gas is moving at high speed there are more opportunities for it
to collide with other molecules. Also as a result of going faster the
collisions will have more force. Heating a gas has a dramatic effect
on the pressure.
Conclusion
My results show a clear correlation between temperature increase and the height achieved when bounced (refer to graph of mean results). This is in accordance with my prediction, which stated that the bounce height would increase with temperature. So this means that heating the ball does give it more energy than it originally had. The sort of energy must be kinetic energy, in the molecules of the rubber and air. Heat energy is also present.
Intermolecular forces of attraction hold solid matter together. These forces can be described to be like springs holding the elastic material together. When a squash ball hits a surface these springs are compressed and stretched. The stretching and compressing of the springs stores the kinetic energy (k.e) of the ball as potential elastic energy (p.e.e). When all the kinetic energy has been stored the spring will release the p.e.e. back into k.e. by returning to their original shape. Some of the kinetic energy is lost during this transition and it becomes heat energy (warming up the springs). So the ball doesn’t bounce back to its original height.
The higher the temperature of the rubber the greater the vibration of the springs and if the temperature becomes hot enough the material melts or leaves as a gas and the springs are broken and the material is no longer elastic but becomes a fluid or gas. Also many elastic materials such as rubber become very brittle at extremely cold temperatures and lose their elasticity and will shatter like glass if they are dropped. This means that the behaviour of the springs holding the matter together is strongly affected by temperature.
Matter in a gas is not held together by intermolecular forces of attraction but is the opposite. The molecules are whizzing about at speed, because they have so much energy that they have broken the intermolecular forces of attraction. In gases the hotter they are the more kinetic energy they have in the form of the molecules moving with more speed.
When a gas is moving at high speed there are more opportunities for it to collide with other molecules. Also as a result of going faster the collisions will have more force. Heating a gas has a dramatic effect on the pressure; in fact there is a law, which states that, in a container of constant volume, Pressure is proportional to Temperature. So if you up the temp you up the pressure.
I conclude that it is mainly the increased pressure of the air within the ball that leads to an increase in bounce efficiency. I can assume that the ball is a container of constant volume, as it is sealed, so the pressure would increase if the temperature were increased. The increase in pressure means that the air molecules inside the ball will be hitting the internal surface more often, which will give the ball more kinetic energy. When the ball deforms it is pushed back into shape by the air. As the air has more kinetic energy the ball will be pushed back into shape faster than it otherwise would. A faster recovery of the original shape means that the ball will push itself off the surface faster and with more force than it otherwise would. Such an occurrence means that the bounce height of the ball will be increased.
The rubber itself also has more energy, which can be found in the molecules making it up. The energy is expressed by the greater vibration of the molecules, stretching and compressing the springs holding it together (felt as heat). When the ball impacts with the surface the springs are stretched and compressed. So the heat of the ball must augment the rebound in the sense that the molecules already have kinetic energy. This also increases bounce efficiency.
EVALUATION
The experiment on the whole was a success in the sense that I obtained
a large range of results. The repeat results were very close together,
which is good because I can assume there were no other significant
variables involved. The results are reliable because I took such a large
range of readings. My evidence easily supports the conclusion I have
come to. Still there are some improvements I would make if I were to
repeat the experiment.
There are a few anomalous results in the experiment (outliers), which is
immediately obvious when you look at the graph of mean results.
The result cannot be ignored, however, for I got the
same reading three times. If I had the result after that reading then
I would be able to see if the curve went back down or if it continued
on that steepness or balanced out there after. For know all I can say
is that it could be a mistake of the reading on my part. Or it could
be a strange property of the ball that at a certain temperature and
bounce height its bounce efficiency suddenly increases dramatically
(which I doubt). I am going to put the result down to human error
because the other two bounce heights don’t display the same property
at that temperature.
Even though there were divertive results (outliers) as this doesn’t undermine my conclusion because it still follows the same pattern of bounce increasing with temperature. It does put the effectiveness of my method and the reliability of my experiment.
Improvements:
There are some improvements I would like to make to my method to
improve the reliability of my results:
- Firstly, after taking the first reading I would place the ball back in the beaker (hot water or cold water) for a minute to ensure that the temperature stays fixed for each height.
- Secondly, I would do some higher and lower temperatures to see if there is a maximum bounce height or if the bounce height gets higher and higher until the ball melts.
-
I would also like to repeat the whole experiment at least three
times to ensure maximum reliability.
