Energy and Matter
I. ENERGY = the capacity for doing work or for transferring heat, measured in
joules (J) or calories (cal).
Chemical and physical changes involve a change in heat energy.
The joule is the SI unit of energy.
The other unit of energy, the calorie = one calorie is the quantity of heat that raises the
temperature of 1g of pure water 1°C.
Symbols: calorie (cal), kilo-calorie (kcalor C); 1 Calorie = 1 kcal = 1000 cal
Conversions: 1J = 0.239 cal
1 cal = 4.18J
Ex: The term “10g of sugar has 41 Calories” means 10g of sugar will release 41 kcal of
heat energy when it is “burned” completely into carbon dioxide and water.
DIFFERENT FORMS OF ENERGY INCLUDE:
CHEMICAL (stored in substances)
ELECTRICAL (produces electric current or flow of electrons)
MECHANICAL (produced by moving parts)
NUCLEAR (comes from reactions in nucleus of atoms)
RADIANT (sunlight, light)
THERMAL (heat gain or loss)
POTENTIAL ENERGY (PE) = stored chemical energy or the energy of position.
KINETIC ENERGY (KE)= energy in use or the energy of motion.
HEAT (q)= a form of energy that is transferred from one body to another because of a
temperature difference.
HEAT transfers from WARMER TO COLDER objects due to the kinetic energy of the
particles.
LAW OF CONSERVATION OF ENERGY, also known as the FIRST LAW OF
THERMODYNAMICS = in ordinary physical or chemical changes/reactions, energy can
be changed from one form to another (inter-converted), but energy cannot be created nor
destroyed. Energy is always conserved and can be accounted for as work, stored energy,
or heat.
II. MATTER: anything that has mass and volume.
Kinetic Molecular Theory of Matter: the tiny particles of matter are in constant motion.
State of
Matter
solid
KE
Particle Motion
Force of Attraction
Very low
Vibrational, in fixed positions in the crystal lattice
liquid
Intermediate
Sliding, passed each other as particles flow
Strong; ionic, covalent,
metallic bonds
Intermediate; van der Waals
gas
Highest
Random, chaotic, with perfectly elastic collisions
Weak; van der Waals
©T. M. Chipi
1
Energy and Matter
LAW OF CONSERVATION OF MASS = in ordinary physical or chemical reactions,
mass is neither created nor destroyed, it just changes from one form to another. Mass is
always conserved and can be accounted for in the mass of the products obtained from the
reactants.
REACTANTS = incoming/starting substances in a chemical reaction; always appear on
the left-hand side of the chemical equation or arrow.
PRODUCTS = outcome/new substances formed from a chemical reaction; always appear
on the right-hand side of the chemical equation or arrow.
CHEMICAL EQUATION = shorthand form of writing a chemical reaction using the
chemical symbols of the substances involved in the chemical change.
REACTANTS  PRODUCTS
The arrow is a shorthand form of saying “ARE CHANGED TO” or “PRODUCE”; it is
read as “YIELDS”.
Δ
EX: calcium + sulfur  calcium sulfide
REACTANTS
YIELD
PRODUCT
PHYSICAL PROPERTIES DESCRIBE THE APPEARANCE OF A SUBSTANCE,
these are observed (using the senses) or measured: color, shape, size, characteristic odor,
characteristic taste, luster, brittleness, hardness, texture, density, magnetic properties,
melting point, boiling point, specific gravity, etc. When physical changes occur, a
physical reaction is taking place and the SUBSTANCE REMAINS CHEMICALLY
UNCHANGED; ONLY THE APPEARANCE CHANGES.
CHEMICAL PROPERTIES DESCRIBE THE ABILITY OF A SUBSTANCE TO
UNDERGO A CHEMICAL CHANGE (a change in its inherent behavior): rust, rot, burn,
ferment, decompose, decay, explode, tarnish, etc. When chemical changes occur, a
chemical reaction is taking place and NEW SUBSTANCES FORM.
PHYSICAL CHANGE
energy may be absorbed (endothermic)
energy may be released (exothermic)
gas/vapor/solid may form
a change in appearance occurs
a change in size/shape/state of matter
process easily reversed
new substance does NOT form
CHEMICAL CHANGE
energy may be absorbed
energy may be released
gas/vapor/solid may form
a change in ability or behavior occurs
a change in color/odor
process not easily reversed
NEW substance forms
PHYSICAL CHANGE/REACTION = a change in the appearance of the materials only.
All phase changes, change size/shape, distillation, solvation, filtration, etc.
CHEMICAL REACTIONS = chemical changes in matter, where one or more substances
are changed into new substances with new and different physical and chemical properties
from those of the reactants. In chemical reactions old chemical bonds are broken
©T. M. Chipi
2
Energy and Matter
(endothermic process) and new chemical bonds are formed (exothermic process) as
reactants change into products.
PRECIPITATE = an insoluble solid that separates from a solution during a chemical
reaction and settles at the bottom of the container.
III. SEPARATION OF MIXTURES: physical separation of two or more pure
substances that does not cause any chemical changes in the components.
1. Centrifuging: a method for separating mixtures of solids or liquids of different
mass/density by rotating them in a tube in a horizontal circle.
2. Chromatography: a technique for separating mixtures of gases, liquids, or
dissolved substances by using polarity/solubility principles between a mobile
phase (solute) and a stationary phase (solvent). Different components of the
sample are adsorbed to different extents according to their solubility/polarity and
moved a certain distance along the solvent at different rates within an allotted
time frame.
3. Crystallization (fractional): a method for separating mixtures of soluble solids that
takes into consideration the solubility of the solute particles in the solvent medium
(temperature dependent solubility). It dissolves the solute(s) in a suitable hot
solvent and then lowers the temperature slowly, forcing the least soluble
component to crystallize out first leaving the other components in solution.
4. Desalination of water through crystallization: one method uses evaporation of the
water allowing for the re-crystallization of the dissolved salt and the condensation
of the water vapor. Another method lowers the temperature while the
solidification of the liquid water into ice crystals forces the salt to adhere to the
outside of the ice structure.
5. Distillation (fractional): the process of separating a mixture of liquids and
dissolved solids in liquids by taking into consideration differences in boiling
points of the solute(s) and solvent. The process entails boiling a liquid,
condensing its vapor, and collecting it after separation from solution. The liquid
collected is called the distillate.
6. Filtration: the process of separating a mixture of solids and liquids that takes into
consideration the solubility and particle size of the solute particles in the solvent
medium. The clear liquid collected through the filter is called the filtrate and the
solid collected on the filter is usually referred to as a precipitate.
IV. SOLUTIONS: homogeneous mixtures
Parts of a solution:
1. solute = substance being dissolved (present in smaller %)
2. solvent = substance doing the dissolving (present in larger %)
3. solution = solute plus solvent
Solvation = process where a solute is dissolved by a solvent. It occurs when the attractive
forces b/w solute and solvent exceed the attractive forces b/w solute-solute particles and
solvent-solvent particles. Solvation where water is the solvent is called hydration.
©T. M. Chipi
3
Energy and Matter
The solvation process can be exothermic [as in NaOH (aq) & MgSO4 (aq)] or
endothermic [as in NH4NO3 (aq)].
Solubility = amount of a solute that will dissolve in a specific solvent under given
conditions of temperature and pressure.
a) Water is considered the universal solvent.
b) A solution in which water is the solvent is called an aqueous solution.
c) A salt is considered soluble if more than 1 gram of the salt dissolves in 100
mL of H20.
d) Soluble salts are assumed to dissociate completely (100%) in aqueous
solution.
e) Dissociation = ionic substance dissolves breaking up into its ions.
NaCl (aq)  Na1+ (aq) + Cl1- (aq)
f) Electrolyte = mixture that contains free ions in solution; conducts electricity.
g) Non-electrolyte = mixture that contains molecules in solution; does not
conduct electricity.
General Solubility Rule: LIKE DISSOLVES LIKE
1. Non-polar substance dissolves non-polar subst. (these are usually organic compounds).
2. Ionic and polar substances dissolve ionic and polar substances due to positive-negative
attractions (+ attracts -).
Factors Affecting Solubility:
1. Nature of solute and solvent: electrolyte or non-electrolyte; ionic, polar or non-polar
substance; as a general rule, “like dissolves like”
2. Temperature: for solids and liquids, higher temperature usually increases the
solubility of the solute in the solvent. For gases, LOWER temperature increases the
solubility of the gas in the liquid solvent.
3. Pressure: pressure does not affect the solubility of solids and liquids b/c these are
incompressible forms of matter. Higher pressure increases the solubility of a gas
(solute) in a liquid solvent.
Saturation = refers to the qualitative condition of a solution at a specified temperature,
where solute particles are in a quantity less than, equal to, or greater than a given amount
of solvent can hold; solutions are unsaturated, saturated, or supersaturated, respectively.
1. Saturated soln = establishes a condition of dynamic equilibrium b/w rate of
dissolving and rate of crystallization: the rate of solvation equals the rate of
crystallization. Saturation establishes a dynamic equilibrium described by an
equilibrium equation: PbI2(s) + H2O(l)⇔Pb2+(aq) + 2I1-(aq)
2. Unsaturated and supersaturated solutions cannot reach equilibrium.
3. Test for supersaturation = drop a small seed crystal, of NaC2H3O2 for example,
and extra solute precipitates out; called seeding.
Factors Affecting the Rate of Solvation:
1. Surface Area: greater surface area (smaller particle size) increases the rate of
solvation b/c more solute particles come into contact with solvent particles.
©T. M. Chipi
4
Energy and Matter
2. Stirring: stirring the solute increases the rate at which it dissolves in the solvent.
Why?
3. Temperature: increasing the temperature (for solids and liquids) increases the rate at
which solute dissolves in solvent b/c it provides the energy required to separate
solute-solute particles and solvent-solvent particles during solvation.
4. For GASES, DECREASING the temperature increases the rate of solvation and
INCREASING the pressure increases the rate of solvation. Why?
Concentration Units: Concentration = amount of solute in a given amount of solvent or
solution.
molesSolute
1. Molarity (M) = LiterSolution = n = mol ;
V
[M] = molar concentration
L
[molarity is dependent on temperature due to the expansion or contraction of particles
which changes volume]
€
molesSolute
2. Molality (m) = kilog ramSolvent = n = mol , referred to as molal concentration
mass
kg
{molality is independent of temperature b/c it uses an exact mass measurement which is
independent of space occupied}
€
V. MEASUREMENTS
Density = mass per unit of volume or the compactness of particles of a substance in a
given space.
Substances expand when temperature ↑ and therefore density ↓
Substances contract when temperature ↓ and therefore density ↑
EXCEPTION: WATER
 when temperature ↑ water expands and density ↓
 when temperature ↓ water ALSO expands and density ↓
Densities of water at: 25°C = .997 g/cm3, 4°C = 1 g/cm3, at 0°C = .917 g/cm3
Specific gravity = comparison or ratio of the density of one substance to that of a
reference substance (usually water at 4 °C), at a given temperature.
Xg
Dsubstan ce cm
1g
cm = x (with NO UNITS)
S. G. = Dwater =
3
3
Hydrometer = instrument used to measure specific gravity.
€
Temperature
= measure of the average kinetic energy of the particles in an
€
object/substance. Measured in Celsius (°C) or Kelvin (K) degrees.
The absolute temperature scale is the Kelvin scale, which is also the SI unit of
temperature: at absolute zero all particle motion stops or KE = 0.
Temperature Scales are based on the freezing/boiling point of water:
©T. M. Chipi
5
Energy and Matter
Temperature Scale
Celsius
Kelvin
Fahrenheit
Freezing Point
Boiling Point
100 °C
373 K
212°F
0°C
273 K
32°F
Conversions: K = °C + 273
°C = K – 273
VI. HEATING AND COOLING CURVES
CHANGES OF PHASES/STATES OF MATTER
order decreases
entropy
increases:
high entropy
sublimation
GAS
vaporization
condensation
TEMPERATURE
(0C)
cools
warms
LIQUID
melting
freezing
SOLID
order increases
entropy
decreases:
low entropy
deposition
ENERGY (J)
©T. M. Chipi
6
Energy and Matter
VII. SOLUBILITY CURVES: soluble ionic solids in water
©T. M. Chipi
7
Energy and Matter
VIII. SOLUBILITY CURVES: gases in water
Effect of temperature on gases
Effect of pressure on gases
©T. M. Chipi
8
Energy and Matter
VIII. THE TYNDALL EFFECT
IX. SEEDING A SUPERSATURATED SOLUTION
©T. M. Chipi
9