Transcript chem ch 1 and 16

Chapters 1 and 16
 exothermic-
energy is released
in the rxn
 exo- out
 takes 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
 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 carbon
2. organic- study of substances
containing carbon
subst from living things
1. basic research- carried
out for the sake of
increasing knowledge
chance discoveries can
occur and have
changed our lives!
2. applied researchcarried out to solve
problems
depletion of ozone layers
by CFCs led scientists to
develop new refrigerants
 technological
developmentproduction and
use of products
that improve
our quality of
life
 Which 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
many forms of matter
fundamental building
blocks of matter:
atoms and molecules
What’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
subst
 usu made from 2 or more kinds of
atoms
 used to distinguish between subst
and to separate them
 help to reveal unknown subst
 ALL matter has many properties by
which it can be grouped
 properties are either intensive or
extensive
 do 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
 DO 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
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 state
 phy 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  MgO
parts of chem rxn:
1. reactants- the substances that react in the
chem rxn
arrow points AWAY FROM reactants
products- the subst that are
formed by the chem chg
arrow ALWAYS POINTS TO
products
3. arrow stands for yields
2.
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
 tremendous variety of forms of matter
 can be categorized into 2 groups:
1. pure substance- composition is same
thruout
 can be elements or compounds
2. mixture- contains more than 1 subst;
can vary in composition and
properties
 every sample has a fixed composition
 H2O (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
 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:
 homo- same
 looks the same
thru-out
 uniform in
composition
 aka- solutions
 may be solids,
liquids, gases
solvent- part that does
the dissolving
usu water
aka- the universal solvent
1.
2. solute- part that is
dissolved
 hetero- 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 composition
 ex: gold, mercury, hydrogen
substances composed of more
than one kind of atom always
arranged in definite ratios
ex: copper II sulfate, CuSO4
sucrose, C12H22O11
one or more subst are used
up
1 or more new subst are
formed
energy is absorbed or
released
 color change
 formation of precipitate (ppt)
 gas bubbling
 energy changes- heat, light
 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
 occur with NO changes
in the composition
 can be:
 chgs of state
 cutting/breaking
 dissolving
 distillation
 fractional
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)
older unit used is calorie
1 cal = 4.184 J
food calorie is a larger unit
1 CAL = 1 000 cal
convert 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
 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
 Will 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 HEAT
 amount 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/goC
 table 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-Ti
when 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?