Atms and Mlecules Mlecules are made f smaller entities (atms) which are bnded tgether. Therefre mlecules are divisible. Miscnceptin: Element and atm are synnyms. Prper cnceptin: Elements are atms with the same number f prtns in the nucleus; atms with different numbers f prtns are different elements. Miscnceptin: Mlecules are basic, simple, indivisible entities. Prper cnceptin: Mlecules are made f smaller entities (atms) which are bnded tgether. Therefre mlecules are divisible. Elements are the simplest substances in nature that cntain smallest particles called atms, and all atms f the same element have identical chemical prperties. When atms f different elements are jined tgether in grups, they frm mlecules. Pure substances and mixtures Matter is anything that has mass and takes up space, and is always either a pure substance (i.e., an element r cmpund) r a mixture f substances. Cmpunds are made f tw r mre kinds f atms held tgether chemically (bnded). Mixtures are frmed when elements and/r cmpunds are cmbined physically. Cmpunds pssess their wn set f prperties and these prperties are different frm the prperties f the elements that frm them. We get energy frm the cmpunds that make up ur fd. Miscnceptin: Air is a substance. Prper Cnceptin: Air is a mixture f substances, mstly nitrgen and xygen, but als small amunts f water, carbn dixide, and ther gases. Classifying matter is imprtant because we are able t predict behavir and prperties based n the material s characteristics. Fr example, we knw that we can separate sugar frm water in a sugar slutin because it is a mixture f tw cmpunds. We cannt, hwever, separate the hydrgen frm the xygen in water withut breaking strng chemical bnds within the water mlecule. Miscnceptin: Particles pssess the same prperties as the cmpunds they frm. Prper cnceptin: Cmpunds pssess their wn set f prperties and these prperties are different frm the prperties f the elements that frm them. Matter is classified as pure substances and mixtures. A Pure substance is a single element r cmpund, and a mixture is frmed as a result f cmbining different cmpunds and/r elements.
Mvement f Particles in Slids, Liquids, Gases, and Plasmas states Mlecules themselves d nt expand. A heated substance may appear t expand because heat causes mlecules t mve faster (and further apart). Miscnceptin: Gases have n mass. Prper Cnceptin: Gases cntain matter whse particles are relatively far apart frm each ther, s their density is lwer than mst liquids and slids. Miscnceptin: Mlecules expand when heated. Prper cnceptin: Mlecules themselves d nt expand. A heated substance may appear t expand because heat causes mlecules t mve faster (and further apart). Miscnceptin: At abslute zer mtin f every part f an bject stps. Prper Cnceptin: Temperature is a quantity that measures hw fast the atms and mlecules which make up the bject mve r scillate. As an bject is cled the scillatins f its atms and/r mlecules slw dwn up t a pint in which this scillatins are the slwest they can pssible be. The temperature which crrespnds t this pint is called abslute zer.
Physical and Chemical Prperties f Matter Matter can be described by its physical and chemical prperties. Miscnceptin: Mass and vlume, which bth describe an "amunt f matter, are the same prperty. Prper Cnceptin: Mass is a measure f the amunt f matter. Vlume is the amunt f space that matter ccupies. Miscnceptin: Weight and mass is the same thing. Prper Cnceptin: Mass is a measure f the amunt f matter that frms (r cmpses) an bject. Weight is the result f the frce f gravity n the mass f an bject. Characteristics f matter, called prperties, are used t help us understand hw and why matter underges the changes that it des, r t predict hw matter will behave under cnditins nt yet bserved r studied. Prperties can be classified as physical r chemical, depending n whether r nt the prperty can be bserved withut anther (different) substance present. Chemical elements pssess their wn characteristic prperties, (density, biling pint, melting pint, slubility, etc.) and these prperties are used t distinguish ne element frm anther. The prperties f a substance are thse characteristics that are used t identify r describe it. A substance has characteristic prperties which are independent f the amunt f the sample. Physical prperties are readily bservable and will retain the same cmpsitin (nthing new is created). Clr, size, dr, luster, hardness, melting pint, biling pints, cnductivity, density(mass divided by vlume) Changes in state f matter (melting, biling, freezing, cndensing) d nt create a new substance and retain their riginal cmpsitin and is therefre a physical prperty. Chemical prperties are nly bservable during a chemical reactin and allws fr change (smething new is created). The prperty is the ability t change whereas the change is the actin itself. Reactivity (describes hw easily smething reacts with smething else), cmbustibility (a substance r material that is able r likely t catch fire and burn) Physical prperties f substances are thse prperties that can be bserved, and measured, withut changing the cmpsitin f the substance as cmpared t chemical prperties as thse that can be bserved and measured when the substance is underging change.
Changes in Matter as Physical r Chemical Changes f state are physical changes. Mlecule shape, size and mass d nt change as a material changes frm ne state t anther. Even thugh a material s appearance varies depending n its state, the mlecules f that material have nt changed. The difference in state (and appearance) is the result f changes in the frces (and average distance) between them. Changes in matter can als be classified as chemical r physical, depending n whether a new substance is frmed frm the starting materials. During phase changes, the particles that make up the material mve apart r clser tgether, depending n whether energy is being added r taken away. Whether the change is physical r chemical, the ttal amunt f matter always stays the same, even thugh the materials may appear much different after the change as cmpared t befre. When matter underges change, it always invlves energy mving int r ut f the system, ften in the frm f heat. When energy is absrbed by the system, the atms gain kinetic energy, ptential energy, r bth. When energy leaves the system, the atms lse kinetic energy, ptential energy, r bth. Every spntaneus prcess ccurs in the directin f decreasing (lwering) the energy f the system. After a chemical change, the prducts may be changed back int the riginal reactants nly thrugh anther chemical change. After a physical change, the cmpnents may be separated r united by ther physical changes. Energy is invlved in chemical and physical changes. As the energy f particles changes, their mvement changes and the phase in which matter is present might change. As particles are expsed t increasing levels f energy, their speed f mvement increases and they will experience a change f phase Physical change- any change in size, shape, r frm, r state where the identity f the matter stays the same Ex. Melting, freezing, cndensing, evaprating, breaking, cutting, bending Chemical changes are assciated with the frmatin f a precipitate (the calcium carbnate precipitated frm egg shell), evlutin f a gas (baking sda and vinegar, hydrgen perxide and liver r ptat), clr change (apple, fd clring), and energy change (sugar) Chemical change- ccurs when ne type f matter changes int a different type f matter with different prperties Substances befre a chemical change are reactants. After a chemical change, the new substances are frmed, they are termed prducts. After a chemical change, the prduct cannt g back t its riginal reactants. Many reactins invlve heat. Sme prduce a gas- bubbling. Frmatin f precipitate (t cause a slid t separate ut frm a slutin) and changes in clr are als bservable evidence. Ex. Burning, digestin, respiratin, phtsynthesis, decmpsitin, rusting, fermenting Classic evidences fr chemical changes include the frmatin f a gas, slid; clr change; change in temperature; r emissin f light. Unfrtunately, many physical changes are als accmpanied by these characteristics. The main difference between physical and chemical changes is what types f bnds yu are breaking r frming during the prcess. Bnds WITHIN a substance requires chemical
changes, because new substances are frmed. Bnds BETWEEN substances are frmed and brken during physical changes; n new substances are frmed in these prcesses. Miscnceptin: Physical changes are reversible; chemical changes are nt. Prper Cnceptin: Physical changes are thse in which ne r mre physical prperties change but n new substances are frmed; Chemical changes invlve the frmatin f a new substance that exhibits chemical prperties different frm the starting materials. Mst cmmn physical and chemical changes are reversible, but sme are mre difficult (require mre energy) t accmplish. Miscnceptin: Materials change temperature during phase changes. Prper Cnceptin: During phase changes, energy is either absrbed t vercme attractive frces between particles, r lst when particles stick tgether. Since the temperature des nt change in these transfrmatins, the average velcity f particles in bth phases is the same during these prcesses. Miscnceptin: Phase changes always invlve energy ging int the system. Prper cnceptin: Phase changes frm mre rdered t less rdered states invlves an absrptin f energy (e.g. slids t liquids); energy is evlved in the reverse prcess (e.g. liquids t slids). Miscnceptin: Phase changes are chemical changes. Prper cnceptin: Althugh this is less cut and dried than sme surces wuld suggest, during a phase change n new substances are frmed s it is classified as a physical change. Miscnceptin: The signs f a chemical change (gas evlutin, clr change, precipitate frmatin, heat prduced) are definitive evidence t be used t classify a prcess. Prper cnceptin: The signs f chemical change are nt definitive and if applied as such, can lead t grss mislabeling f prcesses. Fr example, if a cup f yellw dye is mixed with a cup f blue dye, the green clr that results is nt definitive evidence f a chemical change. These markers shuld be applied with cautin and with ther bservatins befre a cnclusin is drawn abut the nature f a particular prcess. Miscnceptin: Heat and temperature are synnyms Prper cnceptin: Heat is a frm f energy that mves frm a htter bject twards a clder ne. Temperature is a measure f the average relative mtin f the particles that cmpse a material. Heat is an extensive prperty [a prperty which depends n the size f the sample bserved such as mass/vlume] while temperature is an intensive [prperty independent f the size f sample such as melting pint, biling pint, clr] ne. Miscnceptin: All chemical and physical changes are exthermic. Prper cnceptin: Energy is released when bnds frm. Energy is absrbed when bnds are brken. In exthermic reactins the prducts pssess less energy than the reactants. Energy is released when the bnds frm, and energy is required fr a bnd t be brken. Miscnceptins: Mlecules f slids are hard; mlecules f gases are sft; Mlecules f slids are cubes; mlecules f gases are rund; Mlecules f slids are biggest; mlecules f gases are smallest. Prper Cnceptin: Changes f state are physical changes. Mlecule shape, size and mass d nt change as a material changes frm ne state t anther. Even thugh a material s appearance varies depending n its state, the mlecules f that material have nt changed. The difference in state (and appearance) is the result f changes in the frces (and average distance) between them. Miscnceptin: Physical change means yu can get the substance back; after a chemical change can t. Prper Cnceptin: After a chemical change, the prducts may be changed back int the riginal reactants nly thrugh anther chemical change. After a physical change, the cmpnents may be separated r united by ther physical changes.
Peridic Table The Peridic Table f Elements represents ur understanding f the structure and usefulness f the atms that have been identified in ur envirnment. There is a finite number (abut 100) f different kinds f building blcks (elements) that cnstitute the entirety f matter in the universe, frm distant stars t the paper and ink that make up this dcument. The mdern peridic table cntains ver 100 squares fr the elements. They are arranged by increasing atmic number (left t right, up t dwn). The square has the atmic number, atmic mass, element name, and element s chemical symbl. Prperties f an element can be predicted frm its lcatin in the peridic table. Each hrizntal rw f the table is called a perid (7 perids) where each rw represents the number f energy levels present in an atm f the element. The clumns are called grups (18 grups). Elements in each grup have similar characteristics. Metals are lcated n the left, Nnmetals n the right, metallids are in a zigzag line between metals and nnmetals. Elements lcated n the left f the Peridic Table are mst reactive metals, least reactive in the middle, nnmetals n the right. Law f Cnservatin f Matter Matter can neither be created nr destryed but can be changed frm ne frm t anther. Atms are nt created r destryed in chemical reactins. Therefre, the number and kind f atms d nt change. Mass and the number f atms are cnserved. The Law f Cnservatin f Matter, als knwn as the Law f Cnservatin f Mass, states that the ttal mass f the prducts f a reactin is equal t the ttal mass f the reactants. In ther wrds, Matter is nt created r destryed, but nly changes its frm. N matter hw substances within a clsed system interact with ne anther, r hw they cmbine r break apart, the ttal mass f the system remains the same. When atms rearrange themselves t make new substances, energy is ften released r absrbed. Hwever, the ttal amunt f energy befre and after the change is always the same. Miscnceptin: Mass is cnserved, but nt the number r species f atms. Prper Cnceptin: Atms are nt created r destryed in chemical reactins. Therefre, the number and kind f atms d nt change. Mass and the number f atms are cnserved.