General Chemistry I: Chapter 1
General Chemistry I: Chapter 1 CHE 1101
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This 4 page Bundle was uploaded by Hannah Czajkowski on Tuesday February 23, 2016. The Bundle belongs to CHE 1101 at Appalachian State University taught by Jennifer Cecile in Spring 2016. Since its upload, it has received 34 views. For similar materials see General Chemistry1 in Chemistry at Appalachian State University.
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Date Created: 02/23/16
Scientific Measurements Chapter 1 The Scientific Method o Make observations and collect data (i.e. empirical facts) o Form a scientific law (an equation or statement of what happens from data analysis, but doesn’t explain the results) o Form a hypothesis (this explains results and makes prediction) o Create a theory (may never be proven, but supported with evidence and may also change) Matter- anything that has mass and takes up space o Pure substances- matter with fixed compositions and distinct proportions Compounds- consists of two or more elements; combined in the same fixed ration by mass; can be decomposed into elements Elements- can't be decomposed into simpler substances o Mixtures- have variable composition; may be composed of an element or compound, a combination of two or more pure substances; each substance retains its own identity Homogeneous are uniformly mixed, the same properties through the sample aka a solution (air, beer) Heterogeneous - two or more regions or phases present, no uniform composition, properties, or appearance (chocolate chip cookies, salt and pepper) Mass- how much matter is present in a given object; this does not vary from location (earth to space) Weight- the force by which the object is attracted by gravity Chemical Reactions- description of how chemical composition of matter is altered (reactant --> products) o Decomposition reaction shows how one substance is broken down into two or more simpler substances o Elements are material that can't be further decomposed by chemical reactions o Element properties Composed of one atom Simplest form of matter Complex substances vary in elemental combinations Matter Changes o Physical No new substances formed Substance may change state or the proportions Change in a physical property or state, color, density, odor, melting point o Chemical Formation of new substance or compound Involves changing chemical makeup of substances New substance has different physical properties Can't be separated by physical means Chemical property change in oxidation, combustion Properties of Matter o Physical Observed without changing the chemical makeup of a substance Intensive properties do not depend on the amount of substance present (sample size) and are used in substance identity Temperature, melting point Extensive properties depend on the quantity of substances present Mass, volume o Chemical Only observed when a substance undergoes a chemical reaction and is changed into another substance. It can't be separated by physical means and has different physical properties Flammability, corrosiveness, reactivity with acid Experimental Observations o Quantitate- numeric data with measurement Melting point, boiling point, mass, volume o Qualitative- no numerical information, sometimes subjective Sample color, vigorous boiling liquid, product forms white solid Measurements: international system of units o Le Systeme International (SI Units) for consistent measurements o Notice each physical quantity has a different base unit, other measurements derived from SI base units Decimal Multipliers o Giga, G, 10 9 o Mega, M, 10 6 3 o Kilo, k, 10 o BASE o Deci, d, 10 -1 o Centi, c, 10 -2 -3 o Milli, m, 10 o Micro, u, 10 -6 o Nano, n, 10 -9 o -12 Pico, p, 10 Common Chemistry measurements o Length SI Unit meter (m), but large for most measurements Usually centimeter (cm) or millimeter (mm) 1 cm=10 m=0.01m o Volume 3 3 Dimensions of length or m Usually use liters L 1 L = 1 dm 3 1 L = 1000 mL 3 1 mL = 1 cm o Mass SI Unit is kilogram Usually use g 1 kg = 1000 g and 1g = 1000mg o Temperature 3 scales- Kelvin, Celsius, Fahrenheit Measures direction of heat flow Measured with thermometer Measurement Uncertainty o All measurements o are in exact, contain uncertainties or errors o Sources of errors, limitations of reading instruments o Ways to minimize error Take series of measurements Data clusters around central value Calculate average or mean values Report average value Significant figures- the number of digits that express the result to the true measured precision o When founding calculated numbers we pay attention to significant figures so we do not over state accuracy of our answers o All non-zero digits are significant o Zeros between two non-zero numbers are significant o Zeros at the end of a number are significant if a decimal point is written in the number o Final zeros on number without decimal points are not significant o Final zeros to the right of a decimal point are significant o Leading zeros are not significant o Over five round up, under five round down o When multiplication or division is performed, answers are rounded to the number of digits that corresponds to the least number of significant figures in any of the numbers used in the calculation o When addition or subtraction is performed, answers are rounded to the least significant decimal place o Order of operations matter Exact numbers o These numbers come from definitions (12 in. = 1 ft.), number that come from direct count, have no uncertainty o assume they have an infinite number of significant figures. Do not affect number of significant figures in multiplication or division Accuracy- how close measurement is to the true or accepted value (i.e. hitting your target) Precision- how well set of repeated measurements of same quantity agree with each other (target may not have been hit but the outcome was consistent) Dimensional Analysis o Use units to analyze scientific problems o Use conversion factors (simple ratios) to move between one system of measurement and units of another o Given quantity x conversion factor = desired quantity Density- the mass per unit volume, decreases as temperature increases o The SI unit for density is kg/m 3 g/cm for solids g/mL for liquids g/L for gases o If we know the mass and volume of a sample then we can calculate its density
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