CHEM 1000 Lecture : Chemistry 1000 first day lecture notes - September 9th

Experimental outcomes in chemistry depend on making sound observations, taking precise measurements and accurately recording them directly in to the laboratory notebook. All experiments and therefore the results will contain errors (experimental error), which can adversely affect the reliability of the experiment and the credibility of the scientist. Experimental error is reduced when students master experimental techniques and become aware of which measurements have the most impact on the experiment in terms of accuracy and precision. Accuracy is determined by comparing the true or actual value to an individual experimental value or the average of many experimental values. If the true value is not given, the average of all the experimental values is assumed to be true value and accuracy is determined by comparing the average to the individual experimental values. Precision is a determined by comparing how close all the experimental values are to each other. The following data was collected by students in your laboratory section. Decide which value to you will use to complete the experimental calculations. The amount of error in your final experimental result depends on your decision. Each student used a different balance and weighed the beaker 4 times. The balances they used in the laboratory read to a hundredth of a gram. The results are shown below were recorded by each individual. What additional information about the students, instruments, and the conditions which the data was collected do you need to better of the evaluate the reliability of the experimental data? Give 1 and briefly (60 words or less, using complete sentences) explain your answer. Which set of data is the most precise? Show all equations and calculations. Briefly (60 words or less, using complete sentences) explain your answer. What student measurements are the least accurate? Briefly (60 words or less, using complete sentences) suggest how this student could improve their experimental techniques. Show all equation and calculations

Review Sheet for Chemistry 130 Final Exam Matter: Anything that takes up space and has mass Physical Changes and Chemical Changes Define each. How can you tell the difference between the two? Classify the following as physical or chemical changes a spoiling of milk b. bending wire c. cutting paper d. rusting of a nail Put the following into a graphic organizer/flowchart and define each: Matter Pure substances-elements and compounds Mixtures - homogeneous (solutions) and heterogeneous Identify the following as pure substances, homogeneous mixtures or heterogeneous mixtures: a. copper b. sweetened tea c. sand and water d. calcium carbonate (CaCO) Sketch particles in the three states of matter. How close are the particles and how much do they move? Solid Gas Measurements > Define: . Accuracy Precision If Angela masses a the same beaker 3 times and her measurements were 25.43 grams, 24.23 grams, . and 25.98 grams, respectively, were her measurements precise? Explain. If the known mass of the beaker was 26.25 grams, was Angela's measurements accurate? Explain. > Find the Percent Error: When you react 65.39 grams of zinc metal with 72.92 grams of hydrochloric However, you obtained acid, you should obtain 136.30 grams of zinc chloride as one of the products. only 128.72 grams of zinc chloride. What is your percent error? Significant Figures: Count the significant figures in each of the following measurements b. 54.320 meters d. 3.0050 milliliters a. 0.00325 grams c 0.1500 liters