Lab Report free essay sample

Heat it to 90 C and hold this temperature for 10 minutes. 2. Cool it to 50 C in a bath of ice water. 3. Shake the culture bacteria to free it from lumps and add to the milk. 4. Transfer the inoculated milk into the beaker or jar. Cover. 5. Incubate the milk for 4 hours at 43 to 46 degrees until clotted. Clotting of milk indicates the bacteria utilized the sugars and underwent fermentation. 6. Chill for 1 – 2 hours 7. Stir the yogurt to make the texture smooth. 8. Package and consume III. Results and Discussion Kind of Milk| Taste| Color| Texture| Smell| Low- fat milk| Yogurt-like| Beige| Smooth| Sour| Full-cream milk| Very Sour| Beige| Thick| Very sour| In the table above, the reason why there were only 2 kinds of milk is because 2 groups used low fat milk and the other 2 used full-cream milk. As being compared from the table above, using full-cream milk caused the taste and the smell of the product (yogurt) to be extra sour. We will write a custom essay sample on Lab Report or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page Yogurt is naturally sour because of the acid present in it. Also, the full-cream milk caused the texture to be thicker compared to the yogurt used with low-fat milk. Even though different kinds of milk were used, the color of the yogurt was the same, which was Beige. IV. Conclusion Based on the given results and discussion of the data, the characteristics (taste, color, texture, and smell) of the yogurt will depend on what kind of milk will be used for the yogurt making process. V. Recommended If one were to do the same experiment above, the group would recommend that they use low-fat milk to make their own yoghurt. Lab Report free essay sample While observing the information in table 4, it appears that the number of fish changes from time to time and the oxygen increases and / or decreases when this occurs. 2. Develop a hypothesis relating to the amount of dissolved oxygen measured in the water sample and the number of fish observed in the body of water? According to my hypothesis, once there is more dissolved oxygen in the water, there is an increase to the amount of fish present in the area where the water sample is obtained. 3. What would your experimental approach be to test this hypothesis? First, I would take a sample from different areas of the water to test the amount of dissolved oxygen in the water. Then after completing this test, I would check to see if there is† of course â€Å"an increase in the fish present in the water. This observation would help keep track of the fish present in different areas of the water and furthermore, I would be able to compare results. We will write a custom essay sample on Lab Report or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page 4. What would be the independent and dependent variables? Independent= Dissolved Oxygen Dependent= fish 5. What would be your control? I would have control in conducting a hypothesis during my testing. Otherwise, I have no control. 6. What type of graph would you appropriate for this data set? Why? A line graph would be appropriate for this data set. The line graph would not only support the hypothesis but will also present clear results. . Graph the data table from table 4: Water Quality vs. Fish Population. Describe what your graph looks like. (X-axis)= fish and the (y-axis)= dissolved oxygen. 8. This graph would show the fish population increase positioned at the y-axis and the dissolved oxygen increase would be positioned at the x- axis. In the line graph, for example, if there is an oxygen level of 2(ppm) there would be 1 fish present in the water Lab Report free essay sample Joe Schmoe Period 3 March 8, 2013 Lab Report: Empirical Formula of Zinc Chloride (ZnCl) * Purpose The purpose of this experiment was to learn how to determine the empirical formula. Empirical means â€Å"based on experimental evidence. † * Experimental Design The reaction that occurred was the reaction of the elements Zinc (Zn) and Chloride (Cl) by mixing a piece(s) of Zinc and 50mL of Hydrochloric Acid (HCl). The amount of Zinc was determined to be between 1. 00g and 1. 25g. As the reaction occurred there was still water left in the beaker. In order to remove the water we heated the beaker to evaporate it. The Zinc Chloride then formed as a solid white substance. * Observations As the Zinc and Hydrochloric Acid reacted, bubbling and fizzing occurred. The water became cloudy as the Zinc began to decompose and break apart. The Hydrogen in the Hydrochloric Acid was being released as vapors. * Data amp; Evaluation The mass of our beaker was 58. We will write a custom essay sample on Lab Report or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page 78g. Our piece of Zinc was massed at 1. 24g. Therefore, the combined mass of the beaker and Zinc was 60. 02g. After the reaction and heating, the combined mass of the Zinc Chloride and the beaker was 61. 39g. We heated the substance again to remove any excess water. The combined mass of the beaker and Zinc Chloride was then 61. 36g. To find the mass of the reacted Zinc Chloride we subtracted the mass of the beaker (58. 78g) from the total and the mass of the Zinc Chloride came out to be 2. 58g. Subtracting the mass of the Zinc (1. 24g) from the Zinc Chloride mass, we found the mass of just the Chloride was 1. 34g. * Conclusion To find the Empirical formula we first needed to find the number of moles of each element per the mass of each element. You must divide the obtained mass of an element by the atomic weight of that element. 1. 24g Zn ? 1 mol Zn65. 4g Zn= . 018 mol Zn 65. 4g represents the atomic weight of the Zinc on the periodic table 1. 34g Cl ? 1 mol Cl35. 5g Cl= . 037 mol Cl .018 mol Zn. 018 mol Zn=1 . 037molCl. 018molZn=2. 05 The empirical formula of Zinc Chloride is ZnCl2. 05. The accepted formula for Zinc Chloride is ZnCl2. Our answer may be slightly off because of there may be leftover water that was not evaporated. As a result, the mass of the Chlorine would be higher and that would make the moles of Chlorine higher, causing the ratio of Chlorine to Zinc to be slightly higher than 2. Another error that could have been made is if the Zinc Chloride was heated too much and it began to release chlorine. Do so would make the mass of chlorine decrease, which would make the moles of Chlorine decrease and the ration of Chlorine to Zinc be slightly lower than 2. Lab Report free essay sample ABSTRACT This test (ASTM C136-06) determines the grading of materials being used as aggregates using two parameters (coefficient of uniformity and gradation) from particle-size distribution curve. Sieve analysis consists of shaking the sample through a set of sieves that have progressively smaller openings. To conduct a sieve analysis, samples are oven dried for at least 24 hours. The soil is placed and shaken through a stack of sieves with openings of decreasing size from top to bottom. The mass of particles retained in each sieve is determined. Results showed that the particle–size distribution curve of coarse aggregate is characterized by a steep curve. This means the coarse aggregate is poorly or uniformly graded with small variation in size. Particle-size distribution curve of fine aggregate is characterized by an S-curve. It is well graded and has a gradation of particle size that spans evenly the size from coarsest to finest. Conclusions drawn from the interpretation of the particle-size distribution curve is supported by computed coefficients of uniformity and gradation which is 6. We will write a custom essay sample on Lab Report or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page 79 and 1. 03 for (well graded) fine aggregates, and 1. 57 and 1. 05 for (poorly graded) coarse aggregate. Significance of the Experiment Particle size analysis is important because it determines the soil gradation, which is an indicator of other soil properties such as compressibility, shear strength, and hydraulic conductivity. A poorly graded soil will have better drainage because of more void spaces. A well graded soil is able to be compacted more than a poorly graded soil. Standard Reference ASTM C136-06 Standard Test Method for Sieve Analysis of Fine and Coarse Aggregates1. Pennsylvania, US: ASTM International, 2006. I. OBJECTIVES After performing this test, the students are expected to: 1. Determine the percentages of various size fraction on the basis of the total mass of the initial dry sample. 2. Determine effective grain size after plotting particle size distribution curve (percent finer versus particle diameter in millimeter). 3. Calculate coefficient of uniformity and curvature and classify aggregates into well graded or poorly graded aggregates based on given criteria for these two parameters. II. EXPERIMENTAL PROCEDURE A. Materials and Equipment Sieves No. 4, 8, 16, 30, 50, 100, and 200 for fine aggregates Sieves No. 1-in. , 3/4-in. , 1/2-in. , and 3/8-in. for coarse aggregates Balance accurate to 0. 1-g for fine and 0. 5 for coarse aggregates Oven Brush B. Methodology 1. Preparation of the Soil Sample. Minimum of 300-g fine and 5-kg coarse aggregates are obtained. These samples are both oven dried for at least 24 hours. 2. Preparation of Equipment. All mass of sieves including the pan are determined. Then, sieves are nested in order of decreasing size of opening from top to bottom. 3. Sieving. The sample is placed in top sieve. The sieves are agitated by hand in a vertical and lateral motion. 4. For course aggregates, the sample is split into two or more batches, sieving each batch individually. The mass of the several batches retained on a specific sieve are combined before calculating the percentage of the sample on the sieve. 5. Sieving is continued for a sufficient period and in such manner that not more than 1 % by mass of the material retained on any individual sieve will pass that sieve during 1 minute of continuous hand sieving. 6. The mass of each size increment is determined on a balance. The total mass of the material after sieving should check closely with original mass of sample placed on the sieves. NOTE: If the amounts differ by more than 0. 3 %, based on the original dry sample mass, the results should not be used for acceptance purposes. C. Data Analysis 1. The mass of soil retained in each sieve is computed by getting the difference of mass of sieve with the retained soil, and the product of no of batches made and the mass of sieves. 2. The percent retained is computed by getting the ratio of mass of retained soil on each sieve, and the initial mass of the sample. 3. The percent finer is computed by getting the sum of mass of soil retained on smaller sieves, subtracting it from the total mass of sample, and dividing the sum by the total mass times 100. 4. Percent finer is plotted on y-axis while the particle size diameter in logarithmic scale is plotted on x-axis. A curve connecting the points is drawn. Logarithmic scale is used to represent grain size information that typically spans many orders of magnitude. 5. Important parameters in computing coefficient of curvature and uniformity such as effective grain size (D10), D30, and D60 are determined from the particle size distribution curve for fine and coarse aggregates. III. RESULTS OF EXPERIMENT Particle-Size Distribution Curve and Determination of D60, D30, and D10 Figure 1. Particle-Size Distribution Curve (Fine Aggregates) Figure 2. Particle-Size Distribution Curve (Coarse Aggregates) IV. DISCUSSION Effective Grain Size (D10). It represents a grain diameter for which 10% of the sample will be finer than it. It can be used to estimate the permeability. The effective grain sizes in fine and coarse aggregate in this test are 0. 14 mm and 10. 4 mm respectively. These values are obtained from the particle size distribution curve shown in Figures 1 and 2. Coefficient of Gradation (Cc). This parameter (also called as coefficient of curvature) can be expressed as: where; D10, D30, and D60 = the particle-size diameters corresponding to 10, 30, and 60 %, respectively, passing on the cumulative particle-size distribution curve. Fine and coarse aggregates are thought to be well graded if their coefficient of curvature (Cc) is between 1 and 3. The calculated coefficient of gradation is 1. 03 for fine and 1. 05 for coarse aggregates. Coefficient of gradation is only one criterion in grading aggregates. Gradation also considers uniformity coefficient which will be discussed in next section. Uniformity Coefficient (Cu). This is defined as ratio of the diameter of a particle of a size that is retained in sieve that allows 60% of the material to pass through, to the diameter of a particle of a size that is retained in a sieve that allows 10% of the material to pass through. This can be simply expressed as: An aggregate is thought to be well graded if the coefficient of uniformity (Cu) is greater than 4 for coarse (gravel) and 6 for fine aggregate (sand). Calculated values for this parameter are 6. 59 and 1. 57 for fine and coarse aggregate. Classification. Coarse aggregate is composed mainly of gravel and crushed stones which pass 3-inches sieve but are retained on No. 4 sieve. Fine aggregates is mostly sand which passes No. 4 sieve but are retained on No. 200 sieve. The experiment showed that the samples used are poorly graded gravel and well-graded sand. Both of the aggregate pass the criteria for coefficient of gradation which value should lie between 1 and 3. Fine aggregate is well graded sand with uniformity coefficient greater than 6. Coarse aggregate coefficient of uniformity is very small and did not exceed 4. Coarse aggregate sample is poorly graded gravel. V. LABORATORY SUGGESTIONS Suggestions for Laboratory Improvement Here are some of my personal suggestions that I believe will help in improving the laboratory: Acquire New Lab Materials/Repair Old Materials. Some of the materials in the laboratory really need repair or replacement. Use and borrowing of some materials and equipment are sometimes on a first-come, first served basis because of limited availability. VI. SUMMARY AND CONCLUSION Coarse aggregate is composed mainly of gravel and crushed stones while fine aggregate is composed of sand. Particle–size distribution curve of coarse aggregate is characterized by a steep curve. This means the coarse aggregate is poorly graded (uniformly graded) and has small variation in size. Particle-size distribution curve of fine aggregate is characterized by an S-curve. Fine aggregate is well graded and has a gradation of particle size that spans evenly the size from coarsest to finest. This conclusion is supported by computed coefficients of uniformity and gradation which is 6. 79 and 1. 03 for (well graded) fine aggregates, and 1. 57 and 1. 05 for (poorly graded) coarse aggregate. Manual sieving procedures can be ineffective because the amount of energy used to sieve the sample is varying. Over-energetic sieving causes erosion of the particles and thus changes the particle size distribution, while insufficient energy fails to break down loose agglomerates. Other References1: Building Research Institute. Concrete Technology. n. d. Breins Engineering. July 4 2013 . Das, Braja. Fundamentals of Geotechnical Engineering. California, USA: Brooks/Cole Thompson Learning, 2000. Grading of Aggregates. n. d. . Office of Water Programs. Uniformity Coefficient. 2012. Sacramento State Office of Water Programs. 3 July 2013 . Lab report free essay sample Osmosis is a process that occurs at a cellular level that entails the spontaneous net movement of water through a semi-permeable membrane from a region of low solute concentration to an area of high solute concentration in order to equalize the level of water in each region. Involved in this process are hypotonic, hypertonic and isotonic solutions. A hypotonic solution is one with a lower osmotic pressure, indicating that the net movement of water moves into the said solution whereas a hypertonic solution is one with a higher osmotic pressure, thus the net movement of water will be leaving the hypertonic solution. Lastly, an isotonic solution entails no net movement of water across a semi-permeable membrane as the two substances involved display osmotic equilibrium. AIM To observe the effect of solutions different levels of NaCl concentration on potatoes, considering the process of osmosis METHOD (see ‘Potato Osmosis’ – exercise document) Generally rigid in structure although slightly bendy Pale yellow in colour Moist All strips appear the same/similar in structure and size at this point Observations – Post-Extraction Strips immersed in 1. We will write a custom essay sample on Lab report or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page 0M NaCl Solution are very soggy, soft and appear shrunken Strips immersed in 100% H2O are very rigid, swollen, turgid and appear larger/longer they are slightly bent and cannot be straightened due to their rigidity Strips become progressively soggier as the solutions they are immersed in are higher in concentration of NaCl (Fig. 2) Potato strips from the same potato arranged in  descending order of concentration to demonstrate the differences in structure post-extraction. Thus, we can state that there appears to be a negative correlation between NaCl concentration and the mass and length of the potato strips, clearly evident in the above graph which shows an exponential decrease in both mass and length. This can also be initially seen in the post-extraction observations  where it is evident that the potato strips immersed in lower NaCl concentration were far more turgid than those immersed in 100% NaCl solution which were flacid and fragile (see strip-comparison in Fig. 2). This occurrence can be explained through the process of osmosis. As mentioned in the introduction, a hypertonic solution is one with higher osmotic pressure meaning that the net movement of water leaves the solution. This would explain the physical changes – the increase in mass and length as well as the increase in turgidity in the potato strips immersed in 100% H2O solutions or low NaCl-concentration solutions. Since the solution it is submerged in is higher in concentration in water molecules, or hypertonic, the water molecules will diffuse into the area of lower H2O-concentration (the potato strip) in order to achieve equilibrium. Alternatively, the decrease in mass and length in the potato strips submerged in highly concentrated NaCl solutions can be explained by its immersion in a hypotonic solution. Hypertonic solutions, as mentioned Potato Osmosis Biology SL ATh before, are described as those with lower osmotic pressure, indicating that the net movement of water moves into the solution. Therefore, as NaCl solution is less concentrated in H2O molecules than the potato strips, the decrease in mass and length and loss of turgidity results from the net movement of water leaving the potato strips, which is higher in osmotic pressure, and diffusing into the solution. Nevertheless, there are several possible sources of error that could have greatly or negligibly affected the outcome of the experiment. First, we must note the varying external factors resulting from an uncontrolled environment – the biology classroom. Primarily, these would include varying temperatures and humidity which could potentially affect the rate of osmosis as increased temperature results in increased diffusion while increased humidity results in an increased number of water molecules. Secondly, we must note the human errors involved, for example, miscalculations in experimental preparations. These would include the miscalculation of solutions leading to an inaccurate concentration of NaCl as well as the possibility of impurities in the NaCl concoction in the first place while imprecise cutting of the potato strips could’ve affected the surface area and thus the rate of osmosis. This leads us to the errors resulting from variances in the substances used. As already discussed previously, differences in surface area of each potato strip caused by imprecise cutting as well as the marks (lines and notches) imprinted would’ve affected the rate of osmosis while the concentration gradient between each potato strip is likely to differ as well. This stems from the differences in water content of each potato, as, for example, a potato with high water concentration in highly concentrated NaCl solution would have a faster rate of erosion. Further affecting factors could include barriers to diffusion such as the size of pores which would also determine the rate of osmosis. All the mentioned errors above hold the possibility of skewing the data. Subsequently, such errors could have an effect on the reliability of the results. The level of accuracy which has been used throughout this investigation would come into question as a combination of these errors would not permit such precision. Values of percentage change have been taken at two decimal places corresponding with the actual values of mass and length, however, this could be seen as far too precise. A better option would have been to take percentage change as whole numbers or at one decimal place. Nevertheless, we attempted to reduce the potential errors through several measures. With surface area, a cork borer was used in order to uniform the size of the potato strips while the varying concentration gradients were controlled through the completion of several trials (three trials with three potatoes) in order to limit error. Furthermore, to control the effects of the external environment, foil was secured over the beaker containing the submerged potato strips. However, if we refer to the graph, we can see the minimum and maximum spread for each data-point is generally close-set while the R2 value, which calculates the spread of the datapoints from the line of best fit, are both relatively high – both around 0. 9. This demonstrable trend indicates a limiting of the amount of error, and thus fairly reliable results despite possible errors. Overall, the results  ultimately seem reliable although it might’ve been even more reliable by reducing the level of precision (decimal places) when recording it. Ultimately, potential improvements will stem from attempting to reduce the amount of error in this investigation, particularly involving controlling the external environment and the miscalculations. To control the external affecting factors, the solution containing the potato strips can be kept overnight instead in a controlled environment with consistent temperatures and humidity. Limiting the human error would be difficult and time-consuming as this would involve Potato Osmosis Biology SL ATh highly-precise instruments or even more focus dedication from the experimenter during preparation. Finally, nothing can be done to uniform the response of the materials used, thus the completion of even more trials limits the potential error and allows the formation of generalizations. Despite the improvements proposed, those relating to limiting human error and completing more trials may prove to be futile as they are not only time-consuming, but the demonstrable trends resulting from this experiment indicate that no further improvements are necessary to reach the desired conclusion. Having established that there is no real need to pursue drastic improvements for the initial experiment, we can now proceed to discuss possible extensions to the investigation. While we already know the results of osmosis on a potato, we may now wish to better understand it. This can be done by recording the progress of the potato’s transformation either (a) over a period of time (perhaps 24 hours) or (b) until it has reached the point of equilibrium. The mapping of this progress would involve the periodic removal of the samples in order to measure its mass and length, after which it can be compiled into a graph to chart the transformation under osmosis. Alternatively, we could compare the progress of a potato to another type of vegetable or fruit in order to ascertain water content of each. Lastly, the submerged potato strips may be subjected to different kinds of environment, particularly, varying humidity and temperature, without the protection of a foil cap. This would reveal how much of an impact environmental factors would have on the osmotic process and how would the effects manifest. In relation to the question of the sailor, this could represent the life-span one would expect when trapped in certain climates. Lab Report free essay sample In this experiment, we fix the time which is 5 second to collect the amount of the water. At the same time, we also observe the characteristic of the flow whether is it laminar, transition and turbulent flow. THEORY: Reynolds number basically determines the transition of fluid flow form laminar flow to turbulent flow. When the value of Reynolds number  is less than 2300, laminar flow will occur and the resistance to flow will  be independent of the pipe wall roughness (e). Meanwhile, turbulent flow occurs when the value of Reynolds number is exceeding 4000. For large viscous force, whereby Re value is less than 2300, viscous effects are great enough to damp any disturbance in the flow and the flow remains laminar. The flow is called laminar because the flow takes place in layers. Any combination of low velocity, small diameter, or high kinematic viscosity which results in Re value of less than 2300 will  produce laminar flow. We will write a custom essay sample on Lab Report or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page As Re increases, the viscous damping of flow disturbances or perturbations decreases relative to the inertial effects. Because of a lack of viscous damping, disturbances are amplified until the entire flow breaks down into in irregular motion. There is still a definite flow direction, but there is an irregular motion superimposed on the average motion. Thus, for turbulent flow in a pipe, the fluid is flowing in the downstream direction, fluid particles have an irregular motion in addition to the average motion. The turbulent fluctuations are inherently unsteady and three dimensional. As a result, particles which pass though a given point in the flow do not follow the same path in turbulent flow even though they all are flowing generally downstream. Flows with 2000 lt; Re lt; 4000 are called transitional.