E. Physical changes may be reversed by changing the temperature. Physical changes alter the composition of the substances involved. Physical properties are not valid characteristics for identifying a substance. Physical properties are mostly extensive in nature. Physical changes are usually accompanied by chemical changes. 3. Select the best statement. A. B. C. D. E. Chemical changes provide the only valid basis for identification of a substance. Chemical changes are easily reversed
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Determining the Limiting Reactant and Percent Yield in a Precipitate Reaction (SMG 6D) AP Chemistry One example of a double replacement (metathesis) reaction is the mixing of two solutions resulting in the formation of a precipitate. In solution chemistry‚ the term precipitate is used to describe a solid that forms when a positive ion (cation) and a negative ion (anion) are strongly attracted to one another. In this experiment‚ a precipitation reaction will be studied. Stoichiometry
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Measuring the enthalpy change of vaporisation of water You should attempt this part of the activity even if you have not seen the demonstration of the practical. 1. Calculate a value for ∆Hvap for water in KJ mol-1 using the data from the demonstration. Also‚ calculate ∆Hvap from the following data gathered by a student; 8100 J were needed to distil 2.95g of water. a) Explain why the boiling tube was surrounded with expanded polystyrene (or other similar insulation)‚ but the condenser was left
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From the experimental data and through its analysis‚ the enthalpy of combustion for the five alcohols were determined; methanol‚ ethanol‚ propanol‚ butanol‚ and pentanol. As the line of best fit in the graph suggests‚ the enthalpy of combustion increased as the sizes of the molecules increased. This was predicted in the hypothesis and proves it to be correct. As seen on the graph‚ the enthalpy of combustion increases from 140kJ/mol for methanol‚ which has the smallest molecular mass‚ to 530kJ/mol
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Determination of the Enthalpy for Decomposition of Hydrogen Peroxide Objective: To construct a coffee cup calorimeter‚ measure its calorimeter constant‚ and determine the enthalpy of decomposition and formation of hydrogen peroxide. Background: This experiment is a classic thermodynamics lab. In it‚ we attempt to measure the enthalpy (H) of a chemical reaction. The main obstacle is that this is a quantity that cannot be measured directly. It instead is observed as heat from one substance is transferred
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Title Page: Module Code: FC 511 2T Module Title: Skills for study Tutor Name: Emma Duffy Assessment title: Formative Lab Report: Enthalpy of Combustion of Butanol Student ID Number: 201233920 Date of submission: 6/3/2017 Past tense recapping what you did in the experiment Present tense explain theory and compare theory THINGS TO IMPROVE : Reference Introduction Discussion Avoid Plagiarism Table of Contents Introduction P.3 Aim Materials
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Using Hooke’s Law‚ apparatus weights and 2 types of spring was computed for the spring constant. By performing more than three trials and increasing the weights 10g per trial‚ the behavior of the spring constant was observed with varying force and displacement. With the spring constant obtained‚ the work done on the spring can also be calculated. II. Introduction The experiment defines elasticity which is the ability of an object to return to its original length and shape after the deforming forces
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Classifying Chemical Reactions Purpose: To observe and differentiate between the four different types of chemical reactions. Variables: The independent variables are the sodium chloride‚ sodium carbonate‚ magnesium‚copper‚ copper (11) sulfate‚ silver nitrate‚ oxygen‚ lead(11) nitrate‚ sodium carbonate‚ copper (11) sulfate pentahydrate. The dependent variables are the chemical reactions that are being looked for. For example decomposition‚ synthesis‚ single displacement or double displacement of compounds
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Clearly‚ his best friend convinced Alex to take some drugs. Alex knew the idea was bad. But Tony has been his best friend since they were in elementary and Alex trusted what his best friend said. In this scenario trustworthiness was used to convince and change Alex’s mind about the use of some drugs. He trusted what his best friend said‚ not thinking of the consequences or the facts that have surrounded him about the use of such substance.
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The Agony of Displacement in "Mrs. Sen’s" The word diaspora (originally the dispersion of Jews outside of Israel from the sixth century b.c.‚ when they were exiled to Babylonia‚ until the present time) refers to the movement of the population from its original homeland. For James Clifford‚ it involves dwelling‚ maintaining communities‚ having collective homes away from home. In order to provide a “defining" model‚ Clifford turns to William Safran’s definition of Diaspora: "expatriate minority communities
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