Chapters 1 and 16 exothermic- energy is released in the rxn exo- out takes place without help endothermic- energy is absorbed in rxn endo- in have to have energy in order to occur the study of the composition of substances and the changes they undergo energy is involved in accomplishing these changes all of those substances are chemicals chemical- substance that has a definite composition water- H2O sucrose- C12H22O11 hematite- Fe2O3 2 major: 1. inorganic- concerns substances that are usually without carbon 2. organic- study of substances containing carbon subst from living things 1. basic research- carried out for the sake of increasing knowledge chance discoveries can occur and have changed our lives! 2. applied researchcarried out to solve problems depletion of ozone layers by CFCs led scientists to develop new refrigerants technological developmentproduction and use of products that improve our quality of life Which of the following could be called matter? anything that has a volume and a mass mass- measure of the amount of matter use a balance to measure volume- amount of space a 3D object takes up many forms of matter fundamental building blocks of matter: atoms and molecules What’s the difference? atom- smallest unit of an element that maintains the chemical identity of that element molecule- smallest unit of a diatomic element or a compound that retains all the properties of that subst elements generally make up molecules these particles make up elements and compounds What’s the difference? elements- pure subst that CANNOT be broken down into simpler, stable subst; made of 1 kind of atom compound- subst that can be broken down into simpler, stable subst usu made from 2 or more kinds of atoms used to distinguish between subst and to separate them help to reveal unknown subst ALL matter has many properties by which it can be grouped properties are either intensive or extensive do NOT depend on the amount of matter examined same for a 0.5g sample as 500kg sample ex: melting point, boiling point, density, conduction of electricity DO depend on the amount of matter present there will be a difference in a 0.5g sample and a 500kg sample ex: volume, mass, amount of energy in sample properties can also be grouped into 2 general categories: 1. physical properties- characteristic that can be observed or measured without changing the identity of the substance ex: color, density, hardness, melting point, boiling point 2. Chemical properties- prop that matter exhibits as it undergoes changes that transform it into different subst easiest to see as matter reacts to form new subst ex: reactivity with oxygen, flammability 1. physical chg- a change in a subst that does NOT involve a chg in the identity of the subst ex: melting, boiling, grinding, tearing, cutting 2. chemical changes- aka chemical reactions- a chg in which the subst is converted into different subst ex: rusting, tarnishing, burning some phy chg are part of an important class of chgs called change of state phy chg of a subst from one state to another 4 main states of matter: STATES OF MATTER FOLDABLE 2. chemical changes- aka chemical reactions- a chg in which the subst is converted into different subst ex: rusting, tarnishing, burning magnesium plus oxygen yields magnesium oxide Mg + O2 MgO parts of chem rxn: 1. reactants- the substances that react in the chem rxn arrow points AWAY FROM reactants products- the subst that are formed by the chem chg arrow ALWAYS POINTS TO products 3. arrow stands for yields 2. ex: p. 10 fig.7 ALL changes (physical OR chemical) will involve energy can be different forms, like heat and light boundaries between phy and chem chgs are not always very clear in any chg, the total amount of energy involved DOES NOT change the Law of conservation of energy tremendous variety of forms of matter can be categorized into 2 groups: 1. pure substance- composition is same thruout can be elements or compounds 2. mixture- contains more than 1 subst; can vary in composition and properties every sample has a fixed composition H2O (by mass, 88.8% O and 11.2% H) every sample has exactly the same characteristic properties properties can be used to identify the subst either elements or compounds blend of 2 or more kinds of matter, each retaining its own identity and properties usu physically combined and can be separated properties of mixture are a combination of the properties of subst that make it up 2 types of mixtures: homo- same looks the same thru-out uniform in composition aka- solutions may be solids, liquids, gases solvent- part that does the dissolving usu water aka- the universal solvent 1. 2. solute- part that is dissolved hetero- different may look different composed of more than one phase separated by boundaries called interfaces substances composed of only one kind of atom ALWAYS have the same composition ex: gold, mercury, hydrogen substances composed of more than one kind of atom always arranged in definite ratios ex: copper II sulfate, CuSO4 sucrose, C12H22O11 one or more subst are used up 1 or more new subst are formed energy is absorbed or released color change formation of precipitate (ppt) gas bubbling energy changes- heat, light exothermic- energy is released in the rxn exo- out tend to take place without help endothermic rxn- energy is absorbed in the rxn endo- inside have to have input of energy to occur occur with NO changes in the composition can be: chgs of state cutting/breaking dissolving distillation fractional crystallization phy and chem chgs ( ) always accompanied by energy changes energy changes occur betw sys and surroundings energy transfer as a result of temp difference is HEAT can measure energy chg using units called Joules (J) older unit used is calorie 1 cal = 4.184 J food calorie is a larger unit 1 CAL = 1 000 cal convert betw units study of the transfer of heat energy that accompany chem rxns and physical chg temp- is a measure of the average kinetic energy of the particles in a sample of matter greater KE, higher temp, hotter it feels K= oC + 273 HEAT- measure of the total amount of kinetic energy of the particles in a sample of matter ALWAYS moves from matter at a higher temp to matter at a lower temp fig 1, p.532 calorimeter- device used to measure the energy given off during chem and phy chgs Will you take a piece of the crust with your finger? Will you stick your finger into the filling of the pie? Why won’t you? Is there a difference? some materials tend to heat up and stay hotter longer than other materials dependent on obj’s SPECIFIC HEAT amount of energy required to raise the temp of 1 g of a subst by 1oC (or 1K) Cp units are: J/(goC) Cp H2O= 4.184J/goC table 1, p.533 use the formula: q = m x Cp x Temp heat = mass x specific heat x (Tf-Ti) when heat is gained, Tf-Ti when heat is lost, Ti-Tf ex: How much heat energy is needed to increase the temp of 755g of Fe from 283oC to 403oC? How much energy must a refrigerator absorb from 225g of water so that the temp of the water will drop from 35.5oC to 5.0oC? What mass of water is required to absorb 470 000J of energy from a car engine while the temp increases from 25.0oC to 82.5oC? Apiece of copper alloy with a mass of 85.0g is heated from 30.0oC to 45.5oC. In the process, it absorbs 523J of heat. What is its specific heat? ex: How much heat energy is needed to increase the temp of 755g of Fe from 283oC to 403oC? How much energy must a refrigerator absorb from 225g of water so that the temp of the water will drop from 35.5oC to 5.0oC? What mass of water is required to absorb 470 000J of energy from a car engine while the temp increases from 25.0oC to 82.5oC? Apiece of copper alloy with a mass of 85.0g is heated from 30.0oC to 45.5oC. In the process, it absorbs 523J of heat. What is its specific heat? any heat lost by 1 quantity of matter must be gained by the other quantity of matter in a system one will lose heat to the other until both are at the same temp (law of conservation of energy) fig 1, p.532 If a piece of gold with amass of 45.5g and a temp of 80.5oC is dropped into 192g of water at a temp of 15.0oC, what is the final temp of the system?