Instructions for completing the redo/make-up for the Trifold Display for the Science Fair Project.

Transcription

1 Instructions for completing the redo/make-up for the Trifold Display for the Science Fair Project. On a piece of standard sized poster board (22 in x 28 in), you will copy the information from the back of his page exactly as it appears. You may print the pages that follow the template to put on your board. This is due by 3/5/18.

2 ph Abstract In this investigation, the effects of heating distilled water on the water s ph are shown. Water dissociates, or breaks apart, at a higher rate when heated. This causes the concentration of hydrogen ions to increase. An increase in the concentration of hydrogen ions is what is being measured as ph. Research Question How does the temperature of water affect the ph of water? Background Research Investigating how temperature impacts ph is essential for anyone who studies the environment. It is important to study ph for many reasons. Dr. Perlman states that ph levels below 5 cause major problems in aquatic environments. He puts forth that ph determines the solubility of nutrients and heavy metals. Dr. Perlman said that ph affects whether organisms can use the nutrients that are dissolved in water. As well, he says that since metals are more soluble in low ph solutions, heavy metals become more toxic when the water becomes more acidic. According to Dr. McGann, low ph destroys ecosystems by killing the organisms that are lower on the food chain. This damages the entire environment. While knowing why studying ph is important, knowing what ph actually measures is essential. In the article, Temperature Dependence of the ph of pure Water, Dr. Clark tells us that ph is a measure of the concentration of excess hydrogen ions. He states that as temperature increases, the ph of the solution decreases. The article, ph Water properties, says that a ph of 7 is neutral. It also states that below 7 you get an acidic solution, while above 7 you get an alkaline, or basic, solution. Both conditions are impact the abiotic components of the environment which will directly impact the biotic components of the environment. This investigation of ph will show its relationship to temperature. Variables Independent Variable: temperature in C Dependent Variable: ph Controlled Variables, or Constants: 500-mL of distilled water, Celsius thermometer, 1000-mL beaker, ph meter, heat source, stirring rod Control Group: Water at 20 C (room temperature) Experimental Group: Water being heated from 0 C to 60 C The Effect of Temperature on ph Hypothesis If temperature increases, then ph decreases because according to the article Temperature Dependence of the ph of Pure Water by Dr. Clark, the concentration of hydrogen ions will increase with an increase of temperature which results in a lower ph. Materials 500-mL distilled water, ph meter, Celsius thermometer, 1000-mL beaker, heat source, stirring rod, thermal gloves, goggles, data table, pencil Procedure 1. Place 500-mL of distilled water at 0 C in a 1000-mL beaker with thermometer and ph meter. Record the ph of the water in the data table. 2. Using thermal gloves, slowly heat the water recording the ph of the water at 10 C, 20 C, 30 C, 40 C, 50 C, and 60 C. 3. Repeat steps 1 and 2 for a total of 3 trials. 4. Place 500-mL of distilled water at 20 C in a 1000-mL beaker with thermometer and ph meter. Measure the temperature of this sample of distilled water and record it as your control group. 5. Clean up Data Graph Temperature Trial 1 Trial 2 Trial 3 ( C) ph ph ph Control Group Experimental Group ph-temperature Graph Temperature ( C) Trial 1 ph Trial 2 ph Trial 3 ph Average of Trials 1, 2, and 3 ph Control Group ph The bar graph best shows the relationship that exists between the independent variable, temperature ( C), on the x-axis, and the dependent variable, ph, on the y-axis. The bar graph shows the average of the three experimental trials, which helps with drawing conclusions regarding the relationship between ph and temperature. The bar graph best shows the control group as compared to the line graph, since the line graph would plot the control group as 1 data point, which would not be clearly identifiable because it would be under a point on one of the other lines. Analysis The results show that as the temperature increases, the ph of the solution decreases. The data indicates that for every 10 C increase in temperature, there is approximately a 0.15 decrease in ph. This trend is only for distilled water, since that is what was used as the control group in this investigation. As shown on the board, and discussed at the beginning of this investigation, H 2O H + + OH -. This means that as temperature increases, the dissociation of water molecules into hydrogen ions and oxygen ions increases. The increase in hydrogen ions is what causes the ph to decrease. There is no data that seems to be outliers, so there is no need to eliminate data. This data shows that increases in temperature cause changes in ph that may in fact influence other systems. Conclusion The data collected supported the hypothesis. The data showed that as temperature increases, the ph of distilled water decreases. This data fits with what current research states about the relationship between temperature and ph. Since ph is decreasing, you can infer that the concentration of hydrogen ions is increasing. Using an ion detector for oxygen ions might give supporting evidence that water is dissociating with increases in temperature. The effect of temperature on the actual probe of the ph meter is unknown and could be a source of weakness and result in error. Not calibrating the ph meter before the experiment could have been another source of weakness and result in error. As well, not having fresh buffering solution to calibrate the ph meter is an issue. To improve this investigation, make certain that you are using a calibrated thermometer and calibrated ph meter. Ensure that the buffer solution is fresh and that the water you are using is laboratory grade distilled water. How does adding a solute, such as salt or sugar, to the water affect the ph? How does temperature affect the ph of these solutions? Should measurements of free oxygen ions and free hydroxide ions be measured along with ph?

3 Abstract In this investigation, the effects of heating distilled water on the water s ph are shown. Water dissociates, or breaks apart, at a higher rate when heated. This causes the concentration of hydrogen ions to increase. An increase in the concentration of hydrogen ions is what is being measured as ph. Research Question How does the temperature of water affect the ph of water? Background Research Investigating how temperature impacts ph is essential for anyone who studies the environment. It is important to study ph for many reasons. Dr. Perlman states that ph levels below 5 cause major problems in aquatic environments. He puts forth that ph determines the solubility of nutrients and heavy metals. Dr. Perlman said that ph affects whether organisms can use the nutrients that are dissolved in water. As well, he says that since metals are more soluble in low ph solutions, heavy metals become more toxic when the water becomes more acidic. According to Dr. McGann, low ph destroys ecosystems by killing the organisms that are lower on the food chain. This damages the entire environment. While knowing why studying ph is important, knowing what ph actually measures is essential.

4 In the article, Temperature Dependence of the ph of pure Water, Dr. Clark tells us that ph is a measure of the concentration of excess hydrogen ions. He states that as temperature increases, the ph of the solution decreases. The article, ph Water properties, says that a ph of 7 is neutral. It also states that below 7 you get an acidic solution, while above 7 you get an alkaline, or basic, solution. Both conditions are impact the abiotic components of the environment which will directly impact the biotic components of the environment. This investigation of ph will show its relationship to temperature. Variables Independent Variable: temperature in C Dependent Variable: ph Controlled Variables, or Constants: 500-mL of distilled water, Celsius thermometer, 1000-mL beaker, ph meter, heat source, stirring rod Control Group: Water at 20 C (room temperature) Experimental Group: Water being heated from 0 C to 60 C Hypothesis If temperature increases, then ph decreases because according to the article Temperature Dependence of the ph of Pure Water by Dr. Clark, the concentration of hydrogen ions will increase with an increase of temperature which results in a lower ph.

5 Materials 500-mL distilled water, ph meter, Celsius thermometer, 1000-mL beaker, heat source stirring rod, thermal glove, goggles, data table, pencil Procedure 1. Place 500-mL of distilled water at 0 C in a 1000-mL beaker with thermometer and ph meter. Record the ph of the water in the data table. 2. Slowly heat the water recording the ph of the water at 10 C, 20 C, 30 C, 40 C, 50 C, and 60 C. 3. Repeat steps 1 and 2 for a total of 3 trials. 4. Place 500-mL of distilled water at 20 C in a 1000-mL beaker with thermometer and ph meter. Measure the temperature of this sample of distilled water and record it as your control group. 5. Clean up.

6 Data Temperature Trial 1 Trial 2 Trial 3 ( C) ph ph ph Control Group Experimental Group

7 ph Graph 7.6 ph-temperature Graph Temperature ( C) Trial 1 ph Trial 2 ph Trial 3 ph Average of Trials 1, 2, and 3 ph Control Group ph The bar graph best shows the relationship that exists between the independent variable, temperature ( C), on the x-axis, and the dependent variable, ph, on the y-axis. The bar graph shows the average of the three experimental trials, which helps with drawing conclusions regarding the relationship between ph and temperature. The bar graph best shows the control group as compared to the line graph, since the line graph would plot the control group as 1 data point, which would not be clearly identifiable because it would be under a point on one of the other lines.

8 Analysis The results show that as the temperature increases, the ph of the solution decreases. The data indicates that for every 10 C increase in temperature, there is approximately a 0.16 decrease in ph. This trend is only for distilled water, since that is what was used as the control group in this investigation. As shown on the board, and discussed at the beginning of this investigation, H2O H + + OH -. This means that as temperature increases, the dissociation of water molecules into hydrogen ions and oxygen ions increases. The increase in hydrogen ions is what causes the ph to decrease. There is no data that seems to be outliers, so there is no need to eliminate data. This data shows that increases in temperature cause changes in ph that may in fact influence other systems.

9 Conclusion The data collected supported the hypothesis. The data showed that as temperature increases, the ph of distilled water decreases. This data fits with what current research states about the relationship between temperature and ph. Since ph is decreasing, you can infer that the concentration of hydrogen ions is increasing. Using an ion detector for oxygen ions might give supporting evidence that water is dissociating with increases in temperature. The effect of temperature on the actual probe of the ph meter is unknown and could be a source of weakness and result in error. Not calibrating the ph meter before the experiment could have been another source of weakness and result in error. As well, not having fresh buffering solution to calibrate the ph meter is an issue. To improve this investigation, make certain that you are using a calibrated thermometer and calibrated ph meter. Ensure that the buffer solution is fresh and that the water you are using is laboratory grade distilled water. How does adding a solute, such as salt or sugar, to the water affect the ph? How does temperature affect the ph of these solutions? Should measurements of free oxygen ions and free hydroxide ions be measured along with ph?