Chapter 2 ReviewScience, Matter, Energy, and Systems

Scientists use a variety of methods to learn about how the physical world works.

The methods fall into a general process. Science is used to search for order in nature. Four important and noteworthy features of the

scientific process are:CuriositySkepticismReproducibilityPeer review

What Do Scientists Do?

Steps Scientists Take When Trying To Understand the Natural World:

Identify a problemFind out what is know about the problemAsk a question to investigateCollect data to answer the questionPropose a hypothesis to explain the data Make testable projectionsTest the projections with further experiments, models, or observationsAccept or reject the hypothesis

Scientists test their hypotheses, models, and method results over and over again to reveal the reliability of these scientific tools.

Science has five limitations- Scientists can not prove or disprove anything

absolutely.Scientists are human thus are not totally free of

bias about their own results and hypotheses.Many systems involve a huge number of variables

with complex interactions.Science involves the use of estimates.Science is limited to understanding the natural

world and cannot be applied to moral questions.

Matter is anything that has mass and takes up space. There are three physical states:

Solid Liquid Gas

There are also two chemical forms: Elements Compounds

We can change matter into different forms, but no matter how hard we try we can never create or destroy matter.

What Is Matter?

Atoms, Molecules, and Ions are the building blocks of matter.

Atoms are the smallest, and more then 3 million atoms could sit side by side on the period at the end of this sentence.Molecules are the basic building blocks of many compounds and an example of molecules are water.

An ion is a atom or group of atoms with one or more net positive or negative electrical charges.

Some forms of matter are more useful than others.Matter quality is the measure of how useful a form

of matter is to humans as a resource.

Organic compounds are the chemicals of life.They contain at least two carbon atoms of one or more other elements.Most of the chemicals in your body are organic chemicals.

The millions of known organic compounds include:

HydrocarbonsChlorinated hydrocarbonsSimple carbohydrates

Matter undergoes Physical, Chemical and Nuclear changes. When matter undergoes physical changes, there is

no change in its chemical composition. When matter undergoes chemical changes, there is

a change in chemical composition of the substances involved.

There are three types of nuclear change: Radioactive DecayNuclear FissionNuclear fusion

What Happens When Matter Undergoes Change?

We can change elements and compounds from one physical or chemical form to another, but we can never create or destroy any of the atoms involved.

These facts, are based on a scientific law known as the Law of Conservation of Matter.

Energy comes in many forms, but there are two major types of energy: Kinetic energy Stored Energy

About 99% of the energy we use to survive, comes from the sun.

The remaining 1% of energy is sold in the marketplace . Commercial energy comes from burning oil, coal, and natural gas. These fuels are called fossil fuels.

What Is Energy and What Happens When It Undergoes Change?

Some types of energy are more useful than others. Energy quality is a measure of the capacity of a

type of energy to do useful work. These are the two types: High-quality energy Low-quality energy

High-quality energy has a great capacity to do useful work.

Low-quality energy is so dispersed that it has little capacity to do useful work.

Energy changes are governed by two scientific laws.

Thermodynamic is the study of energy transformations.

After observing and measuring energy being transformed millions of times, scientists has summarized their results: The First Law of Thermodynamics The Second Law of Thermodynamics

Systems have inputs, flows, and outputs. A system is a set of components that

function and interact in some regular way. Most systems have:

Inputs from the environment Flows of matter and energy within the system Outputs to the environment

What Are Systems and How Do They Respond to Change?

Each system responds to change through giving feedback.

This helps the system to help decide whether and how to change.

It can take a long time for a system to respond to feedback.

Time delays can allow problems to build up until they hit a tipping point– the point at which a fundamental shift in the behavior of the system occurs.

System effects can be amplified through synergy. Synergy occurs when two or more processes

interact so that the combined effect is greater than the sum of their separate effects.

Synergy can be helpful. The synergistic effect of you and a partner

working together, can make your individual systems capable of accomplishing more in the same amount of time.

■ There is no away. According to the law of conservation of matter, no atoms are created or destroyed whenever matter undergoes a physical or chemical change. Thus, we cannot do away with matter; we can only change it from one physical state or chemical form to another.

■ You cannot get something for nothing. According to the first law of thermodynamics, or the law of conservation of energy, whenever energy is converted from one form to another in a physical or chemical change, no energy is created or destroyed. This means that in such changes, we cannot get more energy out than we put in.

■ You cannot break even. According to the second law of thermodynamics, whenever energy is converted from one form to another in a physical or chemical change, we always end up with lower-quality or less usable energy than we started with. No matter how clever we are or how hard we try, we cannot violate these three basic scientific laws of nature that place limits on what we can do with matter and energy resources.

Three Big Ideas