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*m2/s2 • 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 (cp)
heat needed to raise the temp. of 1 g of a subst. by 1 Co
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 = mΔtcp or q = mcΔt
q = heat lost or gained (J) m = mass (usually in grams) cp or c = specific heat (J/g Co)
Δt = change in temp. (Co)