CHEM 11 UNIT 1.ppt

UNIT 1
Introduction to the Nature of
Matter and Chemical Systems

WHAT IS CHEMISTRY?
 Chemistry is the study of matter and the
transformations it undergoes.
 What is matter?
– Anything that has mass and takes up space.

IMPORTANCE OF CHEMISTRY
 Chemistry is all around you.
– Air you breathe
– Food you digest
– Clothes you wear
– Textbook you read
 Chemistry is often said to be the central
science.

SCIENCE V.S. TECHNOLOGY
 How is science different from technology?
 Science:
– Experimental investigation and exploration of natural
phenomena
– Pursues knowledge for its own sake
– Does not cause change in itself
 Technology
– The practical application of scientific knowledge
– Leads to change (for better or for worse)

SCIENCE V.S. TECHNOLOGY (Cont)
 Examples of science:
– What causes the flu?
– How are atoms put together?
– How is genetic information stored and transmitted?
 Examples of technology
– Flu vaccine
– Atomic bomb
– Genetic engineering

SCIENTIFIC METHOD
 Step 1: Defining a problem
- Example: I am sick
 Step 2: Make observations
– Example: I am sick with a stomachache.
 Step 3: Develop a hypothesis
– Example: I am sick due to the spoiled food I ate
for lunch.
 Step 4: Test hypothesis through experiments
– Example: Ask others who ate the same food for lunch if they
got sick.

SCIENTIFIC METHOD (Cont)
 Step 5: Develop a law
– Law: Summarizes the outcome of several experiments that
occur repeatedly and consistently.
– Example: The spoiled food served at lunch makes people sick
with a stomachache.
 Step 6: Develop a theory
– Theory: Explanation for a why a law exists.
– Example: It is the bacteria in the spoiled food that makes
people ill.

SCIENTIFIC METHOD (Cont)
 Theories
– Are never completely certain
– May change as more experiments are
performed.
– A model is a physical picture or mathematical
expression of a theory.
 Example: Model of the atom
 The scientific method must be free of bias.

WHY STUDY MATTER?
MATTER
Energy
Composition
Properties or
behavior
Structure
Natural Laws
Changes
Uses
Disposal

What does the components of
Matter tell us?
 Composition – the kind and amount of
substance(s) a sample of matter contains.
ex. How does the brain work?
Why is water the universal solvent?
 Structure – how its components are arranged
with respect to the other components.
ex. Isomerism

What does the components of
Matter tell us?
 Properties – the characteristic abilities any sample
of matter exhibits
ex. Disposal of biodegradable and radioactive materials
 Changes – how matter behaves in a particular
setting.
- also known as chemical reactions
 Energy – is the capacity to do work (E=mc2)
ex. Potential energy and Kinetic energy

WHAT IS A CHEMICAL SYSTEM?
 Chemical System is anything that is made
the object of study or scrutiny.
System
Sorrounding or
Environment
Boundary/Wall/Brrier
• Real or Imaginary (whether it can
be touched or not)
• Fixed (e.g. glass or metal
container) or flexible (e.g. interface
between two phases such as air-
liquid interface
• Permeable/Semi-permeable (allow
the flow of matter) or impermeable
(no transfer of matter)
• Diathermal (allow transfer of
energy)

Types of Systems
Matter (permeable)
Energy (diathermal)
Energy (diathermal)
matter
Matter
energy
Open system – is
one wherein matter
and energy can be
transferred
Isolated system –
can exchange
neither energy nor
matter with its
surroundings
Closed system –
can exchange
energy with its
surroundings, but it
cannot exchange
matter.
adiabatic
Impermeable
Impermeable

How do Chemical Sytems and
environment interact?
 Law of Conservation of Matter and Energy –
there is no detectable change in the quantity of
matter during a chemical change
example: isolated system

What are the factors that define the
behavior of a chemical system?
Chemical
system
(behavior)
Walls Composition
Environment Physical
Parameters
-the kind and
amount of matter
and energy present
in the system.
Ex. Behavior of men
and women
- Applicable to
open and closed
system
Ex. Eating and
reading
- Pressure (movable
piston)
- Volume
- Temperature

Effect of Pressure and Temperature
Changes
External Pressure
Internal Pressure
SYSTEM
Endothemic process – absorbs energy
from the environment
Exothermic process – releases energy
to the environment

What is Equilibrium?
 Equilibrium – is a dynamic state of the
system characterized by no change with
time in any of the system’s macroscopic
properties.
– ex. Pressure, temperature, amount of matter,
volume
It is a state in which there are no observable changes
as time goes by.

Types of Equilibrium
 Material Equilibrium (Phase equilibrium) –
rate of flow of matter out is equal to the rate of flow of
matter in.
 Chemical Equilibrium – is achieved when:
1.) the rates of the forward and reverse reactions
are equal and
2.) the concentrations of the reactants and
products remain constant
Reactant/s Product/s

Factors that Affect Chemical
Equilibrium
 Chemical Equilibrium represents a balance
between forward and reverse reactions.
 Changes in the following will alter the
direction of a reaction:
– Concentration
– Pressure
– Volume
– Temperature

Le Chatelier’s Principle
 we can predict how an equilibrium system
will respond to a given change by using
Le Chatelier’s Principle:
“When a system at equilibrium is
disturbed by application of a stress, it
attains a new equilibrium position that
minimizes the stress.”

Le Chatelier’s Principle
 in other words, for every action there is an
equal and opposite reaction; whatever you
do to a reaction system, the system will
respond in the opposite direction.

Effect of Changing Concentration on a
Chemical System
 Increasing the concentration of any
component will cause the reaction system
to try to decrease it, by favouring the
opposite side.

3 CH4 (g) + 6 H2O(g) + 4 N2 (g) 8 NH3 (g) + 3 CO2 (g)
 Increase [CH4]; system responds by trying decrease the
[CH4] by making more product. The concentration of
reactants will go down while the concentration of products
goes up.
 In other words, increasing [CH4] in this reaction favours the
creation of product.
Effect of Changing Concentration on a
Chemical System

Changes in Concentration
Change Shift in Equilibrium
Increase in [Products] left
Decrease in [Products] right
Increase in [Reactants] right
Decrease in [Reactants] left

Effect of Changing Temperature on a
Chemical System (Thermal Equilibrium)
 Increasing the temperature of a system
will favour the endothermic direction.
 Decreasing the temperature will favour the
exothermic direction.
rate of flow heat out = rate of flow heat in

3 H2(g) + N2 (g)  2 NH3 (g) + 92 kJ
 adding energy causes the system to try to
absorb energy; the endothermic direction is
favoured. More reactant is made and the
amount of product decreases.
 taking energy away favours the exothermic
reaction; in this case products are favoured.
Chemical System

 Increasing the temperature of a system
will favour the endothermic direction.
 Decreasing the temperature will favour the
exothermic direction.
Chemical System

Effect of Changing Pressure on a Chemical
System (Mechanical Equilibrium)
 equal numbers of moles at the same
temperature and pressure have the same
volume.
 increasing pressure has the effect of favouring
the side of the equation with fewer particles.

3 CH4 (g) + 6 H2O(g) + 4 N2 (g)  8 NH3 (g) + 3 CO2 (g)
 in this reaction the reactant side has 13
particles; the product side has 11.
 increasing the pressure will favour the
products.
 decreasing the pressure will favour the
reactants.
Effect of Changing Pressure on a
Chemical System

Effect of Changing Volume on a
Chemical System
 in a closed system reducing the volume
has the effect of increasing the
pressure.
 increasing the volume reduces the
pressure.

Types of Equilibrium
 Thermodynamic Equilibrium – when all
three types of equilibrium exist in a
system
- no tendency towards spontaneous change
because the forces such as mechanical, thermal, material
and chemical forces are constant throughout the system.

1st Law of Thermodynamics
 The total sum of all energy in an isolated
system will never increase or decrease.
 “Law of conservation of energy.”
 Energy cannot be created or destroyed,
only transfer forms.

2nd Law of Therm.
 If two objects are not the same
temperature then:
 Heat will always flow from high to low
temperatures.
o Hot object will decrease in temperature and
cold object will increase in temperature
until they are both the same temperature.

New Idea
 “S” is for “Entropy”
S = Q/T
 Internal Energy / Temperature (absolute)
 Joule/Kelvin

More examples of entropy
 Entropy is randomness. Which is more
random? A or B?
A B

 2nd Law of Therm. says that nature always
goes from order to disorder.
A B

 On the large scale, the ice
“looks” more disordered.
 On the small scale, the solid
phase severely limits where
the molecules could be.
 The ice crystal molecules are
much more ordered than the
free moving liquid water
molecules.

CHEM 11 UNIT 1.ppt

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CHEM 11 UNIT 1.ppt