Chapters 1 and 16

Chemistry

2 types of chemical rxns:exothermic- energy is released in the rxn

exo- outtakes place without help

endothermic- energy is absorbed in rxn

endo- in

have to have energy in order to occur

the study of the composition of substances and the changes they undergo

energy is involved in accomplishing these changes

Chemistry

Which of these items is a chemical?

all of those substances are chemicals

chemical- substance that has a definite composition

water- H2O

sucrose- C12H22O11

hematite- Fe2O3

2 major:1. inorganic- concerns substances that are usually without carbon2. organic- study of substances containing carbon

subst from living things

Branches of Chemistry

Types of research:1. basic research-

carried out for the sake of increasing knowledge

chance discoveries can occur and have changed our lives!

2. applied research- carried out to solve problems

depletion of ozone layers by CFCs led scientists to develop new refrigerants

technological development- production and use of products that improve our quality of life

MatterWhich of the following could be called matter?

anything that has a volume and a mass

mass- measure of the amount of matter

use a balance to measure volume- amount of space a 3D object takes up

Matter

many forms of matterfundamental building blocks of matter:atoms and moleculesWhat’s the difference?

atom- smallest unit of an element that maintains the chemical identity of that element

molecule- smallest unit of a diatomic element or a compound that retains all the properties of that subst

elements generally make up molecules

these particles make up elements and compounds

What’s the difference?

elements- pure subst that CANNOT be broken down into simpler, stable subst; made of 1 kind of atom

compound- subst that can be broken down into simpler, stable substusu made from 2 or more kinds of atoms

used to distinguish between subst and to separate them

help to reveal unknown substALL matter has many properties by which it can be grouped

properties are either intensive or extensive

Properties of Matter

Intensive Propertiesdo NOT depend on

the amount of matter examined

same for a 0.5g sample as 500kg sample

ex: melting point, boiling point, density, conduction of electricity

Extensive PropertiesDO depend on the

amount of matter present

there will be a difference in a 0.5g sample and a 500kg sample

ex: volume, mass, amount of energy in sample

properties can also be grouped into 2 general categories:

1. physical properties- characteristic that can be observed or measured without changing the identity of the substance

ex: color, density, hardness, melting point, boiling point

2. Chemical properties- prop that matter exhibits as it undergoes changes that transform it into different subst

easiest to see as matter reacts to form new subst

ex: reactivity with oxygen, flammability

Matter frequently goes thru changes2 types of changes:

1. physical chg- a change in a subst that does NOT involve a chg in the identity of the subst

ex: melting, boiling, grinding, tearing, cutting

2. chemical changes- aka chemical reactions- a chg in which the subst is converted into different subst

ex: rusting, tarnishing, burning

some phy chg are part of an important class of chgs called

change of statephy chg of a subst from one state

to another

4 main states of matter:

STATES OF MATTER FOLDABLE

2. chemical changes- aka chemical reactions- a chg in which the subst is converted into different subst

ex: rusting, tarnishing, burning

magnesium plus oxygen yields magnesium oxide

Mg + O2 MgOparts of chem rxn:

1. reactants- the substances that react in the chem rxnarrow points AWAY FROM reactants

Chemical Rxn

2. products- the subst that are formed by the chem chgarrow ALWAYS POINTS TO products

3. arrow stands for yields

ex: p. 10 fig.7

ALL changes (physical OR chemical) will involve energy

can be different forms, like heat and light

boundaries between phy and chem chgs are not always very clear

in any chg, the total amount of energy involved DOES NOT change

the Law of conservation of energy

Energy

tremendous variety of forms of matter

can be categorized into 2 groups:1. pure substance- composition is same thruoutcan be elements or compounds

2. mixture- contains more than 1 subst; can vary in composition and properties

Classification of Matter

every sample has a fixed compositionH2O (by mass, 88.8% O and 11.2% H)

every sample has exactly the same characteristic properties

properties can be used to identify the subst

either elements or compounds

Pure Substances

blend of 2 or more kinds of matter, each retaining its own identity and properties

usu physically combined and can be separated

properties of mixture are a combination of the properties of subst that make it up

2 types of mixtures:

Mixtures

1. homogeneous mixtureshomo- samelooks the same thru-out

uniform in composition

aka- solutionsmay be solids, liquids, gases

2 parts to a soln:1. solvent- part that

does the dissolvingusu wateraka- the universal

solvent

2. solute- part that is dissolved

2. heterogeneous mixturehetero- different

may look different

composed of more than one phase

separated by boundaries called interfaces

substances composed of only one kind of atom

ALWAYS have the same compositionex: gold, mercury, hydrogen

Elements

substances composed of more than one kind of atom always arranged in definite ratios

ex: copper II sulfate, CuSO4

sucrose, C12H22O11

Compounds

one or more subst are used up

1 or more new subst are formed

energy is absorbed or released

In chemical changes:

color changeformation of precipitate (ppt)

Evidence of chemical changes:

gas bubblingenergy changes- heat, light

2 types of chemical rxns:exothermic- energy

is released in the rxn

exo- out

tend to take place without help

endothermic rxn- energy is absorbed in the rxn

endo- inside

have to have input of energy to occur

Physical Changesoccur with NO

changes in the composition

can be:chgs of statecutting/breakingdissolvingdistillationfractional

crystallization

phy and chem chgs ( ) always accompanied by energy changes

energy changes occur betw sys and surroundings

energy transfer as a result of temp difference is HEAT

can measure energy chg using units called Joules (J)

Energy

older unit used is calorie1 cal = 4.184 Jfood calorie is a larger unit

1 CAL = 1 000 calconvert betw units

study of the transfer of heat energy that accompany chem rxns and physical chg

temp- is a measure of the average kinetic energy of the particles in a sample of matter

greater KE, higher temp, hotter it feels

Thermochemistry

K= oC + 273

HEAT- measure of the total amount of kinetic energy of the particles in a sample of matter

ALWAYS moves from matter at a higher temp to matter at a lower temp

fig 1, p.532

calorimeter- device used to measure the energy given off during chem and phy chgs

Specific HeatWill you take a

piece of the crust with your finger?

Will you stick your finger into the filling of the pie?

Why won’t you?Is there a

difference?

some materials tend to heat up and stay hotter longer than other materials

dependent on obj’s SPECIFIC HEATamount of energy required to raise the temp of 1 g of a subst by 1oC (or 1K)

Cp

units are: J/(goC)Cp H2O= 4.184J/goCtable 1, p.533

use the formula:q = m x Cp x Temp

heat = mass x specific heat x (Tf-Ti)

when heat is gained, Tf-Tiwhen heat is lost, Ti-Tf

ex: How much heat energy is needed to increase the temp of 755g of Fe from 283oC to 403oC?

How much energy must a refrigerator absorb from 225g of water so that the temp of the water will drop from 35.5oC to 5.0oC?

What mass of water is required to absorb 470 000J of energy from a car engine while the temp increases from 25.0oC to 82.5oC?

Apiece of copper alloy with a mass of 85.0g is heated from 30.0oC to 45.5oC. In the process, it absorbs 523J of heat. What is its specific heat?

ex: How much heat energy is needed to increase the temp of 755g of Fe from 283oC to 403oC?

How much energy must a refrigerator absorb from 225g of water so that the temp of the water will drop from 35.5oC to 5.0oC?

What mass of water is required to absorb 470 000J of energy from a car engine while the temp increases from 25.0oC to 82.5oC?

Apiece of copper alloy with a mass of 85.0g is heated from 30.0oC to 45.5oC. In the process, it absorbs 523J of heat. What is its specific heat?

any heat lost by 1 quantity of matter must be gained by the other quantity of matter in a system

one will lose heat to the other until both are at the same temp

(law of conservation of energy)

fig 1, p.532

If a piece of gold with amass of 45.5g and a temp of 80.5oC is dropped into 192g of water at a temp of 15.0oC, what is the final temp of the system?

Measuring Temp