honors chemistry

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 = mtcp or q = mct

q = heat lost or gained (J) m = mass (usually in grams)

cp or c = specific heat (J/g Co)

t = change in temp. (Co)