HONORS CHEMISTRY Chapter 3 MATTER
CLASSIFICATION OF MATTER
Classification of Matter Matter - anything that has mass and occupies space anything that has the prop. of intertia Material - a specific kind of matter Mixture - matter that contains 2 or more diff. materials Ex. wood, granite, concrete, air, milk
Classification of Matter Heterogeneous Materials - nonuniform material has different properties throughout made of separate phases Phase - Physically separate part of a material having a uniform set of properties Interface - boundary betw. phases
Classification of Matter Heterogeneous Mixture - composed of more than one phase Homogeneous Materials - consist of only 1 phase same props. throughout Heterogeneous materials are always mixtures. Homogeneous mixtures are called solutions.
Mixtures Mixtures can vary in composition Solutions consist of: Solute - dissolved material Solvent - dissolving material Same phase - solvent is in greater proportion Molarity - indicates amt. of solute in a specific amt. of solvent - Concentration
Classification of Matter Substances - homogeneous materials which always have the same composition Divided into 2 classes 1. Elements - substs. composed of 1 kind of atom 2. Compounds - substs. composed of 2 or more diff. kinds of atoms chemically combined
Mixture Vs. Compound MIXTURES not chemically combined separated by physical means proportions may vary COMPOUNDS chemically combined separated only by chemical means proportions can not vary (look up Law of Definite Proportions)
Classification of Matter Organic Substs. - compounds which contain carbon Inorganic Substs. - elements and compounds of all elements other than carbon
PHYSICAL AND CHEMICAL CHANGES
Physical Changes changes in a material in which no new properties appear Ex. boiling, melting, breaking, etc.
Useful Physical Changes Distillation - means of separating substs. by boiling pt. differences Fractional Crystallization - means of separating substs. dissolved in the same soln. by using differences in solubilities Solubility - the amt. of solute that will dissolve in a specific amt. of solvent at a specific temp. (see graph p. 58)
Chemical Changes Changes in which new substs. with new props. are formed. Ex. burning, digestion, baking, etc. Separation of a compound requires chemical change
Conservation of Mass During any chemical reaction, the mass of the products is always equal to the mass of the reactants.
RULE OF THUMB If a precipitate, gas, color change, or energy change occurs, a chemical change has probably taken place.
Precipitate - a solid subst. that forms from a soln.
PHYSICAL AND CHEMICAL PROPERTIES
Physical Property A property that can be observed w/out a change of subst. A discription of the behavior of a subst. undergoing a physical change Extensive Properties - Depend on amt. of matter present Intensive Properties - Do not depend on amt. of matter
LOOK UP Malleability Ductility Tensile Strength (tenacity) Conductivity
Chemical Property A prop. characteristic of a subst. when it is involved in a chemical change Defined in terms of interactions w/ other substs. It is just as important to find out if a subst. does not react as it is to discover if it does react.
ENERGY
SYSTEM Part of the universe under consideration Surroundings - everything else Surroundings do work on the system System does work on the surroundings
HEAT (q) Energy transferred betw. 2 objects bec. of a diff. in temp. flows from high temp. to low temp.
Quantitative measurements of energy changes are expressed in Joules (J). - derived SI unit 1 J = 1kg*m 2 /s 2 1 calorie = 4.18 J 1 Calorie = 1000 calories = 1 kilocal. = 4180 J
Chemical changes are always accompanied by energy change. Endothermic Reaction - Rxn. in which energy is absorbed Products have more energy than reactants. Exothermic Reaction - Rxn. in which energy is given off Products have less energy than reactants.
Rule of thumb for reacting systems Nature tends to run downhill (exothermic). Exothermic rxns tend to take place spntaneously (w/out outside help). Endothermic rxns. usually need external source of energy to take place.
Activation Energy - minimum amt. of energy needed to start a rxn. Calorimeter - device used to meas. energy change in a chem rxn. or physical change
Specific Heat (c p ) heat needed to raise the temp. of 1 g of a subst. by 1 C o In an insulated syst., heat lost by one quantity of matter = heat gained by another. assume no heat lost to surroundings energy flows until 2 reach same temp
q = mδtc p or q = mcδt q = heat lost or gained (J) m = mass (usually in grams) c p or c = specific heat (J/g C o ) Δt = change in temp. (C o )