Chapter 2

Science, Matter & Energy

Janice PadulaClinton Community College

Scientific Method:• EXPERIMENT - An observation of natural phenomena

carried out in a controlled manner so that the results can be recorded, duplicated, and rational conclusions obtained.

• HYPOTHESIS - A tentative (unconfirmed) explanation of or prediction derived from experimental observations.

• MODEL – An approximation or simulation of a hypothesis or system being studied.

• THEORY - A tested and widely accepted explanation of basic natural phenomena or scientific hypothesis.

• LAW - A concise verbal or mathematical statement that is always the same under the same natural or controlled conditions.

Validity of Results• Scientific Results (reputable scientific research)

– Can be disproved – Can establish models theories and laws– Can NOT prove absolute truth

• Frontier Science (like media reports)– Controversial– Not widely tested or accepted

• Consensus Science (open peer review)– Widely accepted in the scientific community

• Junk Science (no peer review)– False information presented in a scientific way that is

meant to be misleading and is not accepted by the scientific community

Types of Matter

– ATOM - The smallest particle of an element that retains the chemical properties of that element.

– ELEMENT - Matter that is composed of only one type of atom.

– MOLECULE - A definite group of atoms that are chemically bonded, i.e. tightly connected by attractive forces.

– COMPOUND - Matter that is composed of 2 or more elements combined in definite proportions.

Law of Conservation of Mass:

• Total mass remains constant throughout a chemical reaction

• ex. 2Hg + O2 ---> 2HgO, where the mass

of the 2Hg = 2.53g and the mass of the 2HgO = 2.73g, the mass of the O2 has to

equal 0.20g.

PROTONS

• PROTONS – are defined as:– positively charged subatomic particles with a

charge of +1.602x10-19 coulombs– found inside the nucleus – composed of 2 up quarks and 1down quark– mass = 1.672622x10-24 g or 1.007276 AMU

* The elements atomic number ( Z#) = # protons

NEUTRON

• NEUTRONS – are defined as – electrically neutral subatomic particle – found inside the nucleus – composed of 2 down quarks and 1 up quark– mass = 1.674927x10-24 g or 1.008665 AMU.

NUCLEUS

• NUCLEUS – is defined as:– core of the atom – centrally located– positively charged– contains most of the atom's mass– very dense – small relative to the overall size of the atom

ELECTRONS

• ELECTRONS – are defined as:– negatively charged subatomic particle with a charge

of -1.602x10-19 coulombs

– leptons

– found outside of the core of the atom

– mass = 9.1x10-28 g or 0.00055 AMU

– travel in orbitals around the nucleus

– mostly empty space

– occupies most of the size of the atom

ATOMS

• ATOMS – are defined as:– smallest particle of an element that retains the

chemical properties of that element– composed of the nucleus (core) surrounded by

electrons

ISOTOPES

• ISOTOPES – are defined as:– Atoms of the same atomic number but different mass

B-10 = Boron has 10 mass units, 5 protons & 5 neutrons

B-11 = Boron also can have 11 mass units, 5p & 6n

C-12 = Carbon has 12 mass units, 6 protons & 6 neutrons

C-14 = Carbon has 14 mass units, 6 protons & 8 neutrons

U-234 = Uranium has 234 mass units, ?

U-235 = ?

U-238 = ?

Periodic Table of Elements

• Periodic Table is a reference table of the 117 elements that are currently identified, 92 are naturally occurring, which are displayed in periods (rows) and families (columns) so that similarities and differences can easily be recognized for use in the sciences

• See handout of Periodic Table• Locate the interactive CD from my webpage and

explore it

Ions and Ionic Compounds

• Ions are atoms or groups of atoms that have lost or gained electrons resulting in an overall positive or negative charges.

• Ionic compounds are compounds formed by the combination of (+) and (-) ions.

(+) ions are called cations(-) ions are called anions

Common Polyatomic Ions

• carbonate ion CO3-2

• sulfate ion SO4-2

• sulfite ion SO3-2

• hydroxide OH-

• phosphate PO4-3

• permanganate MnO4-

• chromate CrO4-2

• dichromate Cr2O7-2

• ammonium NH4+

• oxalate C2O4-2

• bicarbonate HCO3-2

• cyanide ion CN-

• acetate C2H3O2-

• peroxide O2-2

• thiosulfate S2O3-2

• bisulfite HSO3-

Basic Chemicals in ENV 101

H2O – water CO2 – carbon dioxide

O2 – oxygen NO2 – nitrogen dioxide

O3 – ozone SO2 – sulfur dioxide

N2 – nitrogen SO3 – sulfur trioxide

N2O – nitrous oxide NH3 – ammonia

NO – nitric oxide H2SO4 – sulfuric acid

H2S – hydrogen sulfide HNO3 – nitric acid

C6H12O6 – glucose CH4 – methane

CO – carbon monoxide HCl – hydrochloric acid

Organic Compounds

• Hydrocarbons – compounds composed of hydrogen and carbon ex. CH4, methane which is the major component in natural gas

• Chlorinated hydrocarbons – hydrocarbons that have chlorines attached, ex. C14H9Cl5 , an insecticide which has been named DDT

• Simple carbohydrates – simple sugars made up of carbon, hydrogen and oxygen, ex. C6H12O6, glucose which most plants and animals metabolize in their cells to produce energy

Complex Organic Molecules

• Polymers – consisting of a number of basic units (monomers) linked together– Complex carbohydrates – made up of monomers of

simple sugars linked together

– Proteins – formed by monomers of amino acids linked together

– Nucleic acids – linked sequences of monomers called nucleotides

• Genes consist of nucleotides in DNA which carries code needed to make proteins

• Chromosomes are a combination of genes and proteins that make up DNA

Physical States of Matter:

• Solid - Relatively incompressible, has a fixed shape and fixed volume.

• Liquid - Has a fixed volume and takes the shape of its container, fluid, and incompressible.

• Gas (Vapor)- Takes the shape of its container, fluid, and is compressible.

Physical vs. Chemical Change:

• Physical Change = Change that takes place in the form or phase of matter, but not in its chemical identity.

• Chemical Change = Change that involves the combination, recombination, or separation of atoms with each other.

The Balanced Equation

2Al(s) + 3Br2(l) Al2Br6(s)

• The chemicals on the left are the reactants and the right are the products.

• The coefficient in front of the chemical denotes the stoichiometric relationship.

Numerical Subscripts

2Al(s) + 3Br2(l) Al2Br6(s)

• The numerical subscript represents the

number of atoms present in the molecule

– ex. Br2 means that an atom of Br is bonded to another atom of Br

– Therefore: Br-Br = Br2

Phases of Matter

2Al(s) + 3Br2(l) Al2Br6(s)

The subscript letters in parenthesis denote the phase of matter that the chemical is in.

Phase of Matter Symbol

Solid (s)

Liquid (l)

Gas (g)

Aqueous (aq)

Energy

• Kinetic Energy – energy of motion

• Potential energy – energy at rest

• High-quality Energy – high output and ability to do work

• Low-quality Energy – low output

Thermodynamics

• Thermodynamics is the study of heat energy– Endothermic process is positive (+) and

involves the absorption of heat– Exothermic process is negative (-) and involves

the release of heat

• Heat transfer– Conduction – Convection– Radiant

Nuclear Change

• Nuclear reactions case changes within the nucleus of an atom

• Natural Radioactive Decay – occurs when an unstable isotope spontaneously releases particles from the atom Nuclear Fission – occur when isotopes are split apart by bombardment with neutrons (see Figures 2-6 & 2-7 on pg 28)

• Nuclear Fusion – occurs when 2 isotopes join together to form a heavier isotope

• Light is bundles of energy called “PHOTONS” that travel in waves through an electrical and magnetic field. (See Fig 2-8 on pg 29)

• Photons have no mass.

• Photons are released when electrons are de-excited from an excited state.

What Is Light?

What Are Waves?

What’s a Wavelength?

Systems

def. System – a set of components that function and interact together as a unit, which allows them to be studied

Inputs > Flows > Outputs

+ Feedback – change in the same direction- Feedback – change in the opposite direction

Types of Pollutants

Three factors are used to determine how severe a pollutant is:

1. Chemical nature – the many chemical properties that a substance or compound has

2. Concentration – usually measured in ppm = 1part pollutant/1 million parts matter or parts per billion (ppb)

3. Persistence – measure of how long a pollutant will remain in a system

Types of Pollutants (cont.)

• Degradable or non-persistent – easily broken down to safer non-toxic matter

• Biodegradable – complex chemicals that are broken down through biological action (specific bacteria)

• Slowly degradable or persistent – take decades or longer to degrade

• Non-degradable – can not be broken down therefore they remain in the system and can contaminate a whole host of organisms

Synergy

• Synergistic effect – build up of effects that create a heightened or accelerated effect

Ex. Exposure to a drug and drinking alcohol can create a heightened effect that may damage your liver, nervous system, heart etc. for more than the individual effects of each chemical.

Ex. Different perfumes can combine and form noxious fumes in a closed room.

Unsustainable High-Throughput vs. Matter-Recycling Economy

• High-throughput economy – economic growth by a one-way flow of matter and energy resources that produce large amounts of waste

• Matter-recycling economy – economic growth slowing down depletion of matter resources in order to reduce excessive pollution

Sustainable Low - Throughput

• Living more sustainably by reducing the throughput of matter and energy– Not wasting matter & energy– Recycling & reusing matter resources– Stabilizing our population