Chapter 1Chapter 1

The Science of ChemistryThe Science of Chemistry

SCIENCESCIENCE

• Latin Latin – having knowledgehaving knowledge– Study concerned with the observation Study concerned with the observation

and classification of factsand classification of facts– examples:examples:

SCIENTISTSCIENTIST

• Search for relationships that can be Search for relationships that can be used to explain and predict the used to explain and predict the behavior of thingsbehavior of things

• HOW???HOW???

•EXPERIMENTEXPERIMENT

CHEMISTRYCHEMISTRY

• A A Laboratory scienceLaboratory science that deals that deals with the with the composition, structure and composition, structure and propertiesproperties substances and the substances and the changes they undergochanges they undergo

Section 1-1 What is Section 1-1 What is Chemistry?Chemistry?

• Objectives:Objectives:– Describe the characteristics of the three most Describe the characteristics of the three most

common physical statescommon physical states– Draw models to represent solids, liquids & Draw models to represent solids, liquids &

gasesgases– Write a word equation for a chemical reactionWrite a word equation for a chemical reaction– Identify the reactants and products in a Identify the reactants and products in a

chemical reactionchemical reaction– Distinguish between exothermic and Distinguish between exothermic and

endothermic reactionsendothermic reactions

Describe the characteristics Describe the characteristics of the three most common of the three most common physical statesphysical states

– A… States of MatterA… States of Matter

– B… Kinetic Molecular TheoryB… Kinetic Molecular Theory

Physical States Physical States

• solidsolid– fixed volume and shapefixed volume and shape

• liquidliquid– fixed volumefixed volume– shape of container, horizontal top surfaceshape of container, horizontal top surface

• gasgas– takes shape and volume of containertakes shape and volume of container

SodiumSodium MercuryMercury Silicon Silicon Nitrogen Nitrogen NeonNeon

Solid Liquid Gas Solid Liquid Gas Solid Liquid Gas Solid Liquid Gas

S,L,G

The Big Three:The Big Three: Water Water

B. Kinetic Molecular B. Kinetic Molecular TheoryTheory

• KMTKMT

– Particles of matter are always in motion.Particles of matter are always in motion.

– The kinetic energy (speed) of these particles increases as temperature increases.The kinetic energy (speed) of these particles increases as temperature increases.

B. Four States of MatterB. Four States of Matter

• SolidsSolids– very low KE - particles very low KE - particles

vibrate but can’t move vibrate but can’t move aroundaround

– fixed shape fixed shape

– fixed volumefixed volume

B. Four States of MatterB. Four States of Matter

• LiquidsLiquids– low KE - particles can low KE - particles can

move around but are move around but are still close togetherstill close together

– variable shapevariable shape– fixed volumefixed volume

B. Four States of MatterB. Four States of Matter

• GasesGases– high KE - particles can high KE - particles can

separate and move separate and move throughout containerthroughout container

– variable shapevariable shape

– variable volumevariable volume

B. Four States of MatterB. Four States of Matter

• PlasmaPlasma– very high KE - particles collide with very high KE - particles collide with

enough energy to break into enough energy to break into charged particles (+/-)charged particles (+/-)

– gas-like, variablegas-like, variableshape & volumeshape & volume

– stars, fluorescentstars, fluorescentlight bulbs, CRTslight bulbs, CRTs

States of matter demoStates of matter demoStates of matter demoStates of matter demo

The Big Three

Gas Liquid Solid Gas Liquid Solid Gas Liquid Solid Gas Liquid Solid

#8 States of Matter

The Big Three

3 States of Bromine3 States of Bromine

SolidSolid BromineBromine

SolidSolid BromineBromine

LiquidLiquid BromineBromine

LiquidLiquid BromineBromine

Bromine Bromine VaporVapor

Bromine Bromine VaporVapor

Draw models to represent Draw models to represent solids, liquids & gasessolids, liquids & gases

SolidSolidSolidSolid

Kinetic Molecular Theory: Kinetic Molecular Theory: SolidSolid

• particles are tightly packed together in particles are tightly packed together in regular arrayregular array

• particles vibrate about average positionsparticles vibrate about average positions• seldom squeeze past other atomsseldom squeeze past other atoms• results in a rigid material with a small, results in a rigid material with a small,

fixed volume for a given massfixed volume for a given mass• external shape often reflects internal external shape often reflects internal

arrangement of particlesarrangement of particles

LiquidLiquidLiquidLiquid

Kinetic Molecular Theory: Kinetic Molecular Theory: LiquidLiquid

• particles are arranged more randomly particles are arranged more randomly than in solidthan in solid

• particles less confined so that they can particles less confined so that they can move past one anothermove past one another

• particles are a little further apart, thus particles are a little further apart, thus slightly larger, fixed volumeslightly larger, fixed volume

• particles are constantly interacting with particles are constantly interacting with one anotherone another

GasGasGasGas

Kinetic Molecular Theory: Kinetic Molecular Theory: GasesGases

• particles in continuous, random, rapid particles in continuous, random, rapid motionmotion

• collisions between particles are elasticcollisions between particles are elastic• volume occupied by the particles is volume occupied by the particles is

negligibly small effect on their behaviornegligibly small effect on their behavior• attractive forces between particles have a attractive forces between particles have a

negligible effect on their behaviornegligible effect on their behavior• gases have no fixed volume or shape, gases have no fixed volume or shape,

take the volume and shape of the take the volume and shape of the containercontainer

Write a word equation for a Write a word equation for a chemical reaction.chemical reaction.

Identify the reactants and Identify the reactants and products in a chemical products in a chemical reactionreaction

Chemical Reactions:Chemical Reactions:

• A chemical reaction occurs when two or more A chemical reaction occurs when two or more chemical substances are mixed together. chemical substances are mixed together.

• This means that the atoms that were joined This means that the atoms that were joined together in the original substances break apart together in the original substances break apart and rearrange themselves to make a new and rearrange themselves to make a new substance, substance,

• one or more substances may be transformed one or more substances may be transformed into one or more new substances. into one or more new substances.

• This new substance is quite different from the This new substance is quite different from the original substances. original substances.

Chemical Reactions:Chemical Reactions:

• Reactant + Reactant ----> Reactant + Reactant ----> ProductProduct

• Some products of chemical Some products of chemical reactions are heat, light, sound and reactions are heat, light, sound and changes in color. changes in color.

Chemical Reactions:Chemical Reactions:• Examples of Chemical Reactions:Examples of Chemical Reactions: • A sparkler contains magnesium. A sparkler contains magnesium.

This, when lit, reacts with oxygen in This, when lit, reacts with oxygen in the air and produces light and heat.  the air and produces light and heat. 

2Mg + O2Mg + O22 2MgO + Energy 2MgO + Energy

Reactants ProductsYields

Chemical Reactions:Chemical Reactions:

• Examples of Chemical Examples of Chemical Reactions: Reactions:

• The chemicals inside a rocket, The chemicals inside a rocket, when lit, react with the oxygen in when lit, react with the oxygen in the air and produce heat, light and the air and produce heat, light and sound. sound.

• 2H2H22 + O + O22 2H 2H22OO

Distinguish between Distinguish between exothermic and endothermic exothermic and endothermic reactionsreactions

• When chemical reactions occurWhen chemical reactions occur, as , as well as the formation of the products, well as the formation of the products, there is there is also a also a heat energy changeheat energy change which can often be detected as a which can often be detected as a temperature change. temperature change.

• This means This means the products have a the products have a different energy content than the different energy content than the original reactantsoriginal reactants (see the reaction (see the reaction profile diagrams below). profile diagrams below).

Distinguish between Distinguish between exothermic and endothermic exothermic and endothermic reactionsreactions

Distinguish between Distinguish between exothermic and endothermic exothermic and endothermic reactionsreactions

• If the products contain less energy than the If the products contain less energy than the reactants, heat is reactants, heat is releasedreleased or  or  given outgiven out to to the surroundings and the change is calledthe surroundings and the change is called exothermic.exothermic.

• The temperature of the system will be The temperature of the system will be observed to rise in an exothermic change. observed to rise in an exothermic change.

• ExamplesExamples: : – the burning or combustion of hydrocarbon fuels the burning or combustion of hydrocarbon fuels – the burning of magnesium, reaction of magnesium the burning of magnesium, reaction of magnesium

with acids, or the reaction of sodium with water with acids, or the reaction of sodium with water – the neutralization of acids and alkalis the neutralization of acids and alkalis – Thermite reactionThermite reaction

Distinguish between Distinguish between exothermic and endothermic exothermic and endothermic reactionsreactions

• If the products contain more energy than If the products contain more energy than the reactants, heat is the reactants, heat is taken in taken in or or absorbedabsorbed from the surroundings and the change is from the surroundings and the change is calledcalled endothermic endothermic..

• If the change can take place spontaneously, If the change can take place spontaneously, the temperature of the reacting system will the temperature of the reacting system will fall but, as is more likely, the reactants must fall but, as is more likely, the reactants must be heated to speed up the reaction and be heated to speed up the reaction and provide the absorbed heat. provide the absorbed heat.

• Examples:Examples: – the thermal decomposition of limestone the thermal decomposition of limestone