The Foundations of Chemistry: Matter,Energy, and Measurements


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Chemistry the study of matter and the changes that matter undergoesMatter anything that has mass and occupies space made of small building blocks called atoms atoms combine to form molecules molecules can be represented in molecular formulas and models An example of a molecular model is a "ball-and-stick". each element is represented by a particular color States of MatterGas: compressible and assumes the shape & volume of its container Liquid: not compressible;will assume the shape of container; has definite volume Solid: not compressible; has a fixed shape and volume Classification of Matter Substance or Mixture Substance can be either an element or a compound has a definite composition and distinct properties EX Sodium chloride, water, oxygen Element: cannot be seperated chemically EX: iron, mercury, oxygen Compounds: two or more elements chemically combined in definite ratios; cannot be separated physically EX: Salt , water, CO2 Mixture: physical combination of two or more substances that have distinct identities; can be separated physically There are two types of mixtures; homogenous and heterogenous Homogenous: composition of mixture is uniform throughout ex: sugar dissolved in water Heterogenous: composition of mixture is not uniform ex: sugar mixed with iron fillings Filtration: a way to separate mixtures A mixture of a solid and a liquid is poured into a porous medium like a filter paper. The liquid passes through the paper while the solid remains on the paper. Distillation: used to separate sodium chloride solutions The solution is boiled; the water evaporates and is condensed and collected in a receiving flask. The salt is left at the bottom of the boiling flask Chromatography: ink components are separated during this test water begins to move up the paper and passes ink spots; the ink spots dissolve at different rates leaving spots on the paper

Comprehension Check Aluminum foil element Baking Soda compound Milk Homogenous Copper Wire element Air homogenous

Hot fudge sundae heterogenous Shampoo homogenous Sugar water homogenous Peach pie heterogenous

Properties of Matter Physical Property determine without changing the identity of the substance Physical change matter undergoes a change at the macroscopic level, but no change in composition Chemical Property undergoes a change in composition and the way a substance can change or react to form other substances Chemical Change: matter undergoes a change in composition/structure

Conservation of Mass There is no new matter matter is neither created nor destroyed in a chemical reaction in a nuclear reaction significant changes in mass occur during physical and chemical changes the total amount of matter remains costant

Energy the capacity to do work Work: result of force acting on a distance Law of Conservation of Energy: no matter is created or destroyed; total amount of energy is constant Energy can be changed from one form to another; transferred to one object to another Kinetic energy: the energy associated with its motion Potential energy: the energy associated with its position or composition Electrical energy: energy associated with the flow of electrical charge Thermal energy: energy associated with random motion of atoms and molecules Chemical energy: a form of potential energy associated with the position of particles that compose the chemical system Units of Energy Joule(J): the SI unit of energy; named after english scientist James Joule Calorie(cal): the amount of energy required to raise the temperature of 1 gram of water by 1 degree Celsius; 1 calorie=4.184 J Calorie (Cal): nutritional calorie; 1 Cal= 1000 calories Kilowatt(kWh)=3.60x10^6 J Exothermic reactions: energy is released Endothermic reaction: energy is absorbed Temperature the atoms and molecules that are in constant motion give off thermal energy Temperature: measures the thermal energy of a substance Heat: the transfer/exchange of thermal energy caused by temperature difference Fahrenheit: water freezes at 32 degrees; boils at 212 degrees Celsius: water freezes at 0 degrees; boils at 22 degrees Kelvin: no negative temperatures; coldest temp is 0K Heat Capacity: the quantity of heat in joules required to change the temperature of a given amount of substance by 1 degree C Specific heat capacity: when the amount of the substance is expressed in grams and has units of joules per gram per degree celsius: J/g degrees C Energy and Heat Capacity Equations q is the amount of heat in joules m is the mass of a substance in gram s C is the specific heat capacity in joules per gram per degrees C T is the temperatre change in C the triangle symbol means the “the change in”

Scientific Method Hypothesis: prediction concerning a phenomenon/educated guess which can be tested Experiment: hypothesis is tested Data: facts from the observation and measurements Scientific Laws: summary of patterns in brief statements Theory: explanation of the observations and the predications can be tested Scientific Measurements The metric system or SI (international system) is a decimal system based on 10 used in most of the world used everywhere by scientists Units in the Metric System      Measurement Metric SI Length meter(m) meter(m) Volume liter(L) cubic meter(m^3) Mass gram(g) kilogram(kg) Time second(s) second(s) Temperature Celsius(C) Kelvin(K) Comprehension Check A bag of tomatoes is 4.6kg mass A person is 2.0 m tall length A medication contains 0.50g of aspirin mass A bottle contains 1.5L of water volume Temperature Conversion Tc= Tf - 32/1.8 Tf= 1.8Tc +32 K=C+273.15 Comprehension Check 85C------>F -12.2C------>F 335F------->C 20.8F------->C Uncertainty in Measurements Exact: numbers with defined values Inexact: numbers obtained from any other method other than counting Inexact beacause of inaccurately calibrated instruments, human error etc. There are two ways to gauge the quality of a set of measure numbers: Precision: measure of how closely individual measurements agree with each other Accuracy: how closely individually measured numbers agree with the correct or true value Significant Figures use to conveny uncertainty non zero digits are always significant; 1 2 3 etc. Zeros between nonzero digits are always significant; 1005 Zeros at the beginning of a number are NEVER significant. they are place holders; 0.02 1 sig fig Zeros that fall at the end of a number and after  the decimal point are always significant;  0.200g has 3 sig figs. 2.0 has 2 sig figs When a number ends in zeros but contains no decimal point, the zeros are not significant; 130 2 sig figs 10300 3 sig figs Comprehension Check How many sig figs in the following numbers? 7.001 4 0.0107 3 Multiplication and Division the same number of sig figs as the measurement with the fewest sig figs must be used use rounding rules to obtain the correct number of sig figs Addition and Subtraction use the same number of decimal places as the measurement with the fewest decimal places use rounding rules to adjust the number of digits in the answer Conversion Factor Method Equalities use two different units to describe the same measured amount are written for relationship between units of the metric system, US units, or between metric and US units EX: 1m=1000mm A conversion factor a fraction obtained from an equality 1in=2.54cm written as a ratio with numerator/denominator can be inverted to give two conversion factors for every equality may be obtained from information in a word problem Problem Solving: Given and Needed Units To solve a problem Identify the GIVEN Identify the NEEDED write them down write a unit plan to convert the given unit to the needed unit write equalities and conversion factors that connect the units use conversion factors to cancel the given unit and provide the needed unit Density compares the mass of an object to its volume is the mass of a substance divided by its volume Density=mass/volume     g/ml Volume by displacement a solid completely submerged in water displaces its own volume of water the volume of the solid is calculated from the volume difference Density as a Conversion Factor a substance of 3.8 g/ml equates to 3.8g=1ml




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