Environment

SCIENCE, MATTER, ENERGY, AND SYSTEMS

WHAT IS SCIENCE?

Science is: • A field of study focused on discovering how nature works

– happens at a variety of scales • Using that knowledge to describe what is likely to happen

in nature • Based on the assumption that events in the natural world

follow orderly cause-and-effect patterns • Patterns can be understood through observations (by use

of our senses and with instruments that expand our senses), measurements, and experimentation

SCIENTISTS:

• Identify a problem for study • Gather relevant data • Propose a hypothesis that explains the

data

• Gather data to test the hypothesis • Modify the hypothesis as needed

The process is known as the scientific method

HYPOTHESES

What is a “hypothesis”? • A “hypothesis” is an idea or explanation that is tested through study and

experimentation.

• Examples: • Problem: The amount of light in the room effects test scores of the students.

Hypothesis: If we increase the amount of light during studying, student’s performance on test scores will decrease.

• Problem: Too many deer found in residential areas. Hypothesis: Deer prefer to stay closer to human settlements.

SCIENTISTS

• Scientists modify, or revise, the hypothesis as needed. • Scientists share their results

SCIENTIFIC THEORIES AND LAWS: THE MOST IMPORTANT AND CERTAIN RESULTS OF SCIENCE

• Scientific theory • Widely tested and supported by evidence

• Scientific law or law of nature • Well-tested, widely accepted description of what happens repeatedly

and in the same way in nature

WHAT IS MATTER?

• Matter is anything that has mass* and takes up space.

• It exists in three physical states – solid, liquid, and gas.

• *Mass=the constant amount of matter/material in something. Often measured in g or kg. (NOT the same as weight, which depends on gravity)

• Exists in three physical states: solid, liquid, or gas

MATTER CONSISTS OF ELEMENTS AND COMPOUNDS

• Two chemical forms: elements and compounds

• Elements • Have unique properties • Cannot be broken down chemically

into other substances

• Known elements arranged in a chart called periodic table of the elements

MATTER CONSISTS OF ELEMENTS AND COMPOUNDS

• Most matter consists of Compounds • Two or more different elements held together in fixed proportions • Example = H20 (hydrogen and oxygen)

ELEMENTS AND COMPOUNDS ARE MADE OF ATOMS, MOLECULES, AND IONS

• Atomic theory • All elements are made of atoms • Atom is the smallest unit of matter into which an element can be divided

and still have distinct chemical properties • Subatomic particles

• Nucleus of the atom • Protons have positive charge • Neutrons have no charge

• Negatively charged electrons orbit the nucleus

ELEMENTS AND COMPOUNDS ARE MADE OF ATOMS, MOLECULES, AND IONS

• Each element has a unique atomic number • Same as number of protons in nucleus • Example: Carbon (C): 6 protons in its nucleus and an atomic

number of 6

• Example: Uranium (U): 92 protons, atomic number of 92 • Most of an atom’s mass is in its nucleus • Electrons have very little mass compared to protons and

neutrons

ELEMENTS AND COMPOUNDS ARE MADE OF ATOMS, MOLECULES, AND IONS

• Mass number • Number of protons plus neutrons in nucleus • Example: Carbon atom has 6 protons and 6 neutrons in its nucleus – its mass

number is 12. • Example: Uranium atom has 92 protons and 143 neutrons – its mass number

of 235.

• Isotope • Form of an element with same atomic number but different mass number

• Each atom of an element has the same number of protons in its nucleus • The number of neutrons in an element’s nucleus can change • Therefore, the mass numbers can also change

ELEMENTS AND COMPOUNDS ARE MADE OF ATOMS, MOLECULES, AND IONS

• Molecule • Combination of two or more atoms of same or

different elements

• Held together by chemical bonds • Molecules are basic building blocks of many

compounds.

• Examples – water, hydrogen gas, and methane

ELEMENTS AND COMPOUNDS ARE MADE OF ATOMS, MOLECULES, AND IONS

• Ions • An atom or a group of atoms (a molecule) with

one or more net positive (+) or negative (−) electrical charges from losing or gaining negatively charged electrons

• Ions are attracted to other ions with opposite electronic charges (+ to -, and – to +), which leads to ionic bonding and the creation of ionic compounds.

• Example: salt (sodium (Na+) chloride (Cl-))

ELEMENTS AND COMPOUNDS ARE MADE OF ATOMS, MOLECULES, AND IONS

• Acidity • Measure of comparative amounts of hydrogen ions (H+) and hydroxide

ions (OH–) in a volume of water solution

• Measured with pH • Neutral solution has pH equal to 7 • Acidic solution has pH < 7 (more hydrogen ions than hydroxide ions) • Basic solution has pH > 7 (more hydroxide ions than hydrogen ions)

ORGANIC COMPOUNDS ARE THE CHEMICALS OF LIFE

• Organic compounds • Contain at least two carbon atoms

• Exception: methane (CH4) • Types

• Hydrocarbons • Simple carbohydrates

• Macromolecules: complex organic molecules • Complex carbohydrates, proteins, nucleic acids,

and lipids

MATTER COMES TO LIFE THROUGH CELLS, GENES, AND CHROMOSOMES • Cells

• Fundamental units of life • All organisms have one or more cells

• Genes • Sequences of nucleotides within DNA • Instructions called genetic information • Create inheritable traits

• Chromosomes: composed of many genes

MATTER CAN CHANGE

• Physical change – No change in chemical composition – Example: crushing a bottle,

chopping wood, and melting ice

• Chemical change – Change in chemical composition – Example: Carbon dioxide

LAW OF CONSERVATION OF MATTER

• We can change elements and compounds from one physical or chemical form to another

• We cannot create or destroy atoms

WHAT IS ENERGY AND WHAT ARE ITS FORMS

• Energy: ability to do work • Kinetic energy

• Energy of movement • Electromagnetic radiation • Thermal energy

• Potential energy

ENERGY COMES IN MANY FORMS

• Kinetic energy is matter in motion. • Energy of movement

• Examples: running water, a ball rolling down a hill, electrons flowing through a wire (electricity), light, and a mass of air moving (wind)

ENERGY COMES IN MANY FORMS

• Kinetic energy is matter in motion. • Electromagnetic radiation is energy that travels in the form of

waves. • Example: visible light and the spectrum of electromagnetic radiation

from the sun

• Light is made of photons which are produced when atoms heat up.

• Light travels in waves • Light is the only form of energy visible to the human eye.

ENERGY COMES IN MANY FORMS

• Kinetic energy is matter in motion. • Heat/Thermal energy is the total kinetic energy of all moving atoms, ions, or molecules in

an object, a body of water, or a volume of gas such as the atmosphere.

• If the atoms, ions, or molecules in a sample of matter move faster, the matter will become warmer.

• When two objects at different temperatures make contact with each another, heat flows from the warmer object to the cooler object.

• Heat is transferred through radiation, conduction, and convection.

ENERGY COMES IN MANY FORMS

• Radiation is the transfer of heat energy through space by electromagnetic radiation in the form of infrared radiation.

• Heat from the sun reaches the earth • Heat from a fireplace transfers to the surrounding air

• Conduction is the transfer of heat from one solid substance to a cooler one when they are in physical contact. Energy moves from hot to cold.

• Touching a hot object • Electric stove burner heats a pan

• Convection is the transfer of heat energy within liquids or gases when warmer areas of the liquid or gas rise to cooler areas and cooler liquid or gas takes its place.

ENERGY COMES IN MANY FORMS

• Potential energy • Stored energy is potentially available for use. • Examples: a spring, carbon in coal, and water behind a dam • Can be changed into kinetic energy

WHAT IS ENERGY AND WHAT HAPPENS WHEN IT UNDERGOES CHANGE?

• Whenever energy is converted from one form to another in a physical or chemical change:

• No energy is created or destroyed when converted from one form to another (first law of thermodynamics/Law of Conservation of Energy)

• You end up with lower quality or less-usable energy than you started with (second law of thermodynamics)

• Lower quality energy is usually in the form of heat flowing into the environment. • The temperature drops to the point that quality is too low to do much useful work.

ENERGY CHANGES OBEY TWO SCIENTIFIC LAWS

• Energy efficiency • Measure of how much work results from a unit of

energy put into a system

• Improving efficiency reduces waste • Estimate: 84% of energy used in the U.S. is wasted

• Unavoidably because of second law of thermodynamics (41%)

• Unnecessarily (43%)

ENERGY IS RENEWABLE AND NONRENEWABLE

• Renewable energy • Gained from resources that are replenished

by natural processes in a relatively short time

• Nonrenewable energy • Gained from resources that can be depleted

and are not replenished by natural processes within human time scale

ENERGY IS RENEWABLE AND NONRENEWABLE

• Solar energy • 99% of the energy that keeps us warm and supports plants and other organisms

• Commercial energy • Energy sold in the marketplace • Supplements sun’s energy • 90% comes from burning fossil fuels

• Oil, coal, and natural gas

WHAT ARE SYSTEMS AND HOW DO THEY RESPOND TO CHANGE?

• System • Set of components that interact in a regular way • Examples: human body, a cell, a TV set, and an

economy

• Systems have inputs, flows, and outputs of matter, energy, and information

• Feedback can affect their behavior

SYSTEMS AND FEEDBACK LOOPS

• Feedback • Any process that increases or decreases a

change to a system

• Positive feedback loop • Causes system to change further in the

same direction (can lead to tipping point). • Example: Decreasing vegetation in a

valley causes increasing erosion and nutrient losses that in turn cause more vegetation to die, resulting in more erosion and nutrient losses.

SYSTEMS AND FEEDBACK LOOPS

• Negative, or corrective, feedback loop • Causes system to change in opposite

directions • Example: Air conditioner goes on until a

specific temperature is reached and then goes off and the house starts to warm until it reaches a specified temperature and turns the air conditioner on

SYSTEMS AND FEEDBACK LOOPS

• Most systems in nature use negative feedback to enhance long-term stability. • Ecological tipping point

• Natural system stuck in positive feedback loop can reach this point • Beyond this point, system changes so drastically it suffers from severe

degradation or collapse