Prediction
If I double the temperature I would not expect the ball to stay in the air twice as long between the first and second bounce. I think this because as the ball gets hotter the rubber casing will start to become slightly deformed due to the rubber casing being affected by the high temperature. However I do expect the ball to bounce higher and therefore stay in the air longer if I increase the temperature of the ball; this is because the molecules are moving faster, causing the internal pressure to go up which in turn causes the ball to bounce more, because it is inflated.
Preliminary Work
Before I did my experiment I tested my method. I found that the squash ball floated in the water so it needed to be held down for it to be heated up. I also found as I dropped the ball it hit the bottom of the clamp stand so I had to move it so this wouldn’t happen again. Other than these two discoveries I found nothing wrong with my method. It was reliable.
Precise
To make my experiment precise I will time the ball in seconds, tenths and hundredths of a second.
Apparatus
Tri-pod, Bunsen burner, beaker, 1m ruler, stopwatch, squash ball, clamp stand, goggles, matches, 200ml water and tongs.
Method
- Put 250ml of water in the beaker.
- Heat the beaker up until it reaches desired temperature.
- Put the ball in the water.
- Hold it under the water for five minutes at the constant temperature.
- Drop it from 100cm; the top of the 1m ruler.
- Using the stopwatch time how long the ball is in the air for between the first and second bounce.
- Do steps 2 – 5 twice more at the same temperature.
Fair Test
I will ensure my test is fair by dropping the ball on the same surface, from the same height and always use the same ball. The only thing I will change is the temperature.
Accurate
To make the test accurate I will drop the ball from each height three times and then take an average of the three drops, this should eliminate any freak results.
Number and Range
I chose to drop the squash ball at 20°C, 40°C, 60°C, 80°C and 100°C. I thought these were good temperatures at which to drop the ball because they’re evenly spaced out and cover a wide range. I didn’t choose to go up in 10’s because I thought this would be to close together for my experiment.
Safety
To make my experiment as safe as possible I will use tongs to take the ball out of the water. I will also avoid contact between the ball and flame and wear goggles.
Results
Conclusion
I found from my graph and results table that the higher the temperature of the ball the longer the ball stays in the air between the first and second bounce.
The graph clearly shows that the higher the temperature the longer the ball stays in the air for. At 20°C the ball stays in the air for 0.32 seconds compared to 0.46 at 40°C. I predicted that if I doubled the temperature the ball wouldn’t stay in the air for twice as long between the first and second bounce. My prediction was correct because the time in my experiment did not double between 20°C and 40°C, however it almost did.
My experiment proves my theory correct; the ball stays in the air longer between the first and second bounce, this is because the molecules are moving faster, causing the internal pressure to go up which in turn causes the ball to bounce more. This is because the temperature affects the movement of the air molecules (kinetic theory). In other words the higher the temperature the faster molecules will move, and will collide more often with more force.
My results therefore match theory as well.
Evaluation
I think my experiment was a good way of obtaining evidence because it was an accurate and precise way of obtaining the evidence I needed to prove my theory and prediction correct. But it was ever so slightly unreliable; if I pressed the stop watch a moment or two too soon or late then this could produce an inaccurate result. Although I had no odd results I still did an average of the three drops to reduce the chances of an inaccurate result affecting my results graph.
However, I do think my results are accurate; I did each drop three times and took an average. I would be able to tell an inaccurate result by comparing it to the two other drops with that same temperature and seeing if there was a big gap in the time.
The information I fond was useful, it proved my theory correct and allowed me to test my prediction and make my conclusion.
My results were reliable because all my results are close to my average. But however it could have been improved by using a water bath, this would allow the water to be at a constant temperature and I wouldn’t need to keep checking the thermometer. The experiment could also of been made slightly more precise by using pressure pads to time the ball in the air, rather than using a stop watch where there is a slight chance of human error. I could also use a light beam connection to a computer to do the same thing.
The evidence I have collected does support my conclusion. But I could extend my experiment by using a lower temperature such as 0°C. Doing this would prove my theory because the molecules inside the ball would be moving slowly and therefore the ball would bounce very little or not at all.
Another way to extend my findings would be to use different squash balls; they come in different hardness’s. So if a harder ball was heated at 100°C it may bounce higher and stay in the air for longer.
I could prove the kinetic theory right in a different way; I could measure how high the ball bounces on its first bounce, this would confirm my findings.
My evidence is sufficient to support a firm conclusion because it shows the ball stays in the air for longer between the first and second bounce as the temperature goes up, this in turn supports my theory and proves my prediction correct.
