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Investigate the effect of changing the sugar concentration on the rate of respiration of yeast.

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AIM: Investigate the effect of changing the sugar concentration on the rate of respiration of yeast. I am trying to find out about the products of alcoholic fermentation. I will plan a safe procedure that will let me find out about the effect of changing the sugar concentration on the rate of respiration of yeast. I will plan a fair test by keeping all the equipment the same because some may have a different rate of performance than others, which would make my experiment unfair. I will keep the concentration of yeast the same each time, because the same concentration of yeast will make sure it is fair. The concentration of yeast matters, as if more yeast is added; the quicker respiration will take place. Yeast contains an enzyme, and as the quantity of the yeast is increased, the enzyme would increase. As more yeast enzymes are present, it would result in more enzymes available for reaction. I will also use the same type of yeast each time as other species of yeast may act differently under the same conditions. The volume of yeast must be kept to a constant amount for each test because if the volume of yeast was not fairly measured out it could result in more or less reaction taking place with the sugar concentration. I will keep the same temperature of the water the same, as I know temperature is a factor that affects the rate of respiration. Temperature-if the temperature is too high, the enzymes die, but if the temperature is too low, then the enzymes react more slowly. Particles move faster when heated which would result in two things: (a) Particles travel greater distance, resulting in more collisions. (b) Particles moving faster-large proportion of collisions will exceed activation energy, concluding in an increase in the rate of reaction. The molecules start to move around slowly but as the heat level rises the molecules race around quickly. ...read more.


My concentrations: > 20% is 10ml sugar solution and 0ml water > 15% is 7.5ml sugar solution and 2.5ml water > 10% is 5ml sugar solution and 5ml water > 5% is 2.5ml sugar solution and 7.5ml water > 0% is 0ml sugar solution and 10ml water I used my equipment with precision and when measuring out the concentrations in ml inside a measuring cylinder I was careful and accurate. Also while I measured the height of gas produced in the measuring cylinder with a ruler, I measured accurately to the nearest millimetre to make sure my measurements were correct in order to have accurate calculations to find the average volume later on. By using a ruler to measure in centimetres and the nearest millimetre, it was an advantage on using the measuring cylinder's scale in ml that was actually collecting the gas because mm are more accurate than ml. Furthermore, while carrying out the repeat measurements, I noticed that they weren't that far apart, which suggests my results were consistent and reliable due to the accurate measuring. My table of results: Timed in 2 minutes Height of Carbon Dioxide gas produced in cm Concentration Try 1 Try 2 Try 3 20% 2cm 2.7cm 2cm 15% 1.5cm 1cm 2cm 10% 1.5cm 1cm 1cm 5% 1cm 0.8cm 0.7cm 0% 0cm 0.2cm 0.1cm Now I will calculate these results to find the volume of the carbon dioxide produced in the measuring cylinder by using the volume of a cylinder formula below: I measured the radius of the measuring cylinder with a ruler and it was 1.75cm. (r(h e.g. ( x 1.75( x 2 =19.24cm( Once I have worked out the volumes I will take averages for each concentration by adding up all of the 3 tries and then dividing the number by 3. Calculations: 20% concentration try 1- ( x 1.75( x 2 = 19.24cm( try 2- ( x 1.75( x 2.7 = 25.98cm( try 3- ( x 1.75( x 2 = 19.24cm( 19.24+25.98+19.24 = 21.49cm( ...read more.


I would also have to keep the same species, concentration and volume of yeast. The variable I would change would be the temperature and my range of values could be 0(, 10(, 20(, 30(, 40(, 50(. My equipment would include: * 2 x 250cm( beakers * 2 x 10ml measuring cylinders * Rubber tubing * Rubber bung * Boiling tube * Delivery tube * 10ml Sugar solution * Stop clock * Thermometer * 100mm/10cm ruler * Hot supply of water My prediction for this experiment is that the volume of the measuring cylinder will increase according to the temperature. As the temperature gets hotter the volume in the measuring cylinder will increase. But as the temperature reaches 40'c to 45'c we will see that the volume in the cylinder has started to fall as it is starting to denature. After looking at all the experiments data collection you will see a gradual incline in the volume of the measuring cylinder. Scientific reason: Increasing the temperature of the substrate can increase the number of collisions. The Collision Theory In order for a reaction to take place, the reacting substances must collide and energy, called the activation energy, must be reached. If the collision between the particles can produce a lot of energy, then a reaction can take place. For the collision to take place, the particles must collide fast enough and in the right direction. The higher the number of collisions, the faster the rate of reaction. The effect of the temperature upon the rate of reaction can be predicted by using the collision theory. I predict that increasing the temperature would speed up the reaction. This is because when the mixture of glucose and yeast is heated, the molecules would gain energy and move faster and travel a greater distance, which would result in more collisions. Also, the particles are moving faster therefore a large proportion of the collisions would exceed the activation energy, thus speeding the rate of reaction. I must be careful while handling the hot water in the aspect of my own safety. ...read more.

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