The Effect of Temperature on Reaction Time

The Effect of Temperature on Reaction Time
Investigation I was given the task too investigate how the temperature (heat) can effect the reaction time of two chemicals. The two chemicals that I am going to use throughout my investigation are: Ÿ Sodium Thiosulphate Solution which are colourless crystals. Ÿ Hydrochloric Acid which is a colourless substance. Sodium Thiosulphate + Hydrochloric Acid Na2S2O3 +2HCl The only part of my investigation that I shall change during this experiment is the temperature. Everything else that I shall be doing during the investigation shall be kept exactly the same. Things such as: Ÿ The units of time that it takes for two chemicals to react and form a compound. Ÿ The units of measurement that I shall use to pour out the chemicals, cm3 or g/l (grams per litre). Ÿ I shall use the same amount of chemicals during each experiment, to make it a fair test. In order for my findings to be valid the experiment must be a fair one. I will use the same standard each time for judging when the X has disappeared. I will make sure that the measuring cylinders for the Hydrochloric Acid and Thiosulphate will not be mixed up. The amount of Hydrochloric Acid will be 15 cm3 each time, and the amount of Thiosulphate will be fixed at 20 cm3. During the heating stage of the experiment, a water bath will be used to heat up the acid and thiosulphate to the necessary temperature (the water bath will be heated up in units of 5/oC, as this is known to be the most effective and accurate way of reaching an exact temperature.Prediction I predict that as the temperature is increased the rate of reaction will increase. When the temperature is increased the particles will have more energy and thus move faster. Therefore they will collide more often and with more energy. Particles with more energy are more likely to overcome the activation energy barrier to reaction and thus react successfully. All this can be understood better with full understanding. Lets think of the experiment from a different angle. 1. Think in your mind of a large gym hall. 2. In the gym hall there are 20 Year 7 pupils walking about. 3. When a Year 7 pupil touches a wall in the gym; then they are told to walk in a different direction. Also if they coiled with another Year 7 pupil then both of them have too walk in an opposite direction. 4. Then 15 Year 11 pupils were told to walk round the gym hall. They were told if they walk into a wall they had to also walk in a different direction. But if they collide with a Year 7 pupil, then they had to hold hands a produce a bond (compound). 5. Then they did it all over again, this time though the Year 11 pupils were told too sprint round the hall; When the Year 11pupils sprint they are filled with energy (heat). When the Year 11 pupils sprinted they took a shorter time, thus a shorter reaction time. When the Year 11 pupils walked they took a longer period of time, thus a slower reaction time. For a reaction to occur particles have to collide with each other. Only particles with enough energy to overcome the barrier will react after colliding. The minimum energy that a particle must have to overcome the barrier is called the activation energy, or Ea. The size of this activation energy is different for different reactions. If the frequency of collisions is increased the rate of reaction will increase. However the percent of successful collisions remains the same. An increase in the frequency of collisions can be achieved by increasing the concentration, pressure, or surface area. Below is a graph of my prediction; graph goes here Safety Precautions [image] Whilst doing my experiment I must use all safety precautions. Safety precautions such as: Ÿ I will ware safety goggles at all times. Ÿ My chair shall be left under the bench and I shall not sit down. Ÿ I will not eat or drink whilst I am doing my experiment. Ÿ I shall not run or do any horseplay. Ÿ Wash my hands before starting and after I have finished my experiment. Ÿ I shall always use care whilst carrying substances. Ÿ I will always report any accident to my teacher immediately. Ÿ I will work only in a clean environment. No unwanted items shall be left on the table. Equipment [image] The water bath is a peace of a equipment that I shall heat the chemicals up in units of 5/oC. The water bath is known too be one of the most accurate ways of reaching a certain temperature. [image] Test tubes are used for containing chemicals. Wise using chemicals you usually place them in test tubes, they come in all different shapes and sizes. The most common test tube that people use are the ones shown in the picture above. I am going too use a wider/thicker test tube, in my experiment. During the investigation I shall observe and recorded the time needed before I can no longer see the X beneath the two solutions. To do this I shall use a stopwatch. 1. I shall test my reaction time, by starting the stopwatch and quickly stopping it. (the time read on the screen shall be my reaction time) 2. Then I do the excrement. I start the stopwatch as I pore the chemicals into each other, when I no longer can see the X beneath the two substances I stop the stopwatch. 3. Finally I subtract my reaction time away from the chemicals reaction time. Thus I shall be left with the reaction time between both chemicals. My reaction time ? The reaction time of the two chemicals. All of the data that I observe shall be recorded on scatter/line graphs. Effects on my investigation The main effects on my experiment are: Ÿ The room temperature. As I do my investigation, the room temperature shall rise and fall. This could effect the reaction time between the two chemicals. I am unable too control this effect. Ÿ The temperature. (wise heating) As I heat the two chemicals, I can not be certain that it reached the exact temperature needed. I can shorten this problem with a water bath. It still may not reach the needed temperature, but it should be much more accurate. Analysis In this experiment I have found that as the temperature and concentration is increased the time taken for the reaction to take place decreases. This means the rate of reaction increasers as it takes less time for a reaction to take place, so more take place per second. In the temperature experiment the time taken for a reaction to take place decreased by roughly 10 to 15 seconds for every 10�C increase in temperature, with the one anomaly being the 30�C reading. There is also a trend in the increase in rate of reaction as the temperature increases. Using the graphs, with lines of best fit, (that plot temperature and concentration against time taken for the reaction to take place) the graphs have negative correlation in both cases, meaning that as the temperature\concentration increased the time taken for the reaction to take place decreases. The time graph for the temperature experiment has a much steeper curve than the one for the concentration experiment, meaning that the decrease in time taken for the reaction was far more rapid. For this to fully make sense it is necessary to recap the collision theory briefly: For a reaction to occur particles have to collide with each other. Only a small percent result in a reaction. This is due to the energy barrier to overcome. Only particles with enough energy to overcome the barrier will react after colliding. The minimum energy that a particle must have to overcome the barrier is called the activation energy, or Ea. The size of this activation energy is different for different reactions. If the frequency of collisions is increased the rate of reaction will increase. However the percent of successful collisions remains the same. An increase in the frequency of collisions can be achieved by increasing the concentration, pressure, or surface area.

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