Chapter 1

Matter, Energy & Change

Chapter Objectives

TSW be able to define chemistry and explain its application as a physical science.

TSW have a solid understanding of how our universe is composed of different arrangements & combinations of the known 118 elements.

TSW be able to differentiate between physical and chemical properties and physical and chemical changes

TSW be able to distinguish between intensive and extensive properties

TSW be able to identify changes as endothermic or exothermic and display an understanding that energy is involved in all changes of matter.

Science Defined

The pursuit of knowledge obtained by observing natural events & conditions in order to discover facts & formulate laws & theories that can be validated through testing.

Research

Basic: investigations carried out for the sake of gaining knowledge

Applied: investigations carried out to find a solution to a specific problem

Technology

The application of scientific discoveries or knowledge to for practical purposes or as a way to improve or simplify life

Technology development and scientific discoveries tend constantly grow cyclically

Chemistry Defined

Chemistry studies the composition,

structure, and properties of matter, the

processes that matter undergoes, and

the energy changes that accompany

these processes.

Concise Definition…

Chemistry is the study of matter, its properties, the changes it undergoes and the energy involved.

Chemistry: a physical science

Physical Science includes the branches of science concerned with the study of inanimate natural objects:

Chemistry

Physics

Astronomy

Branches of Chemistry

Chemistry’s Reach

Chemistry as a discipline requires critical thinking, keen observation, articulate communication, creative problem solving and attention to detail…as you develop and sharpen these skills through this course, you will be better prepared for any path you pursue.

Matter is…

By definition matter is anything that has mass and volume (or takes up space)

Since everything has mass and takes up space…everything we see and touch is composed of matter.

The “Building Blocks” of matter are called atoms.

Mass vs. Weight

These two words are commonly (incorrectly) used as synonyms but, they truly have different meanings.

Mass is a measure of how much matter is in a sample

Weight is a measure of a force acting on a sample

Inertia

a property of matter by which it continues in its existing state of rest or uniform motion in a straight line, unless that state is changed by an external force.

Objects at rest or in motion will remain that way until acted upon by an outside source

Properties of Matter

Every pure substance, regardless of state, has a definite set of unique physical and chemical properties that exist even in their smallest size sample.

We can use these properties to identify a pure substance.

Intensive & Extensive

Some properties depend on the amount of the substance present and others do not… An Intensive property is one that

does not depend on the amount of substance present.

An Extensive property is one that is dependant on the amount of the substance present.

Physical Properties

A physical property is one which can be observed in the absence of a chemical change.

Mass

Density

MP/BP

Conductivity

Color

Malleability

Physical State

Every element, compound or

molecule has a unique

combination of these properties

that allow us to use them in

separating them from a mixture.

Density…

Density is a very useful intensive property.

We can observe that each substance has its own unique value…thus we can determine the density of any unknown and use it to determine the substances identity.

The formula for density is

D = mass / volume

Physical Changes

Any change a substance undergoes that does not involve a change in identity.

Can you think of any?

Chemical Properties & Changes

A Chemical Property is one that can only be observed during the course of a chemical change.

A Chemical Change or Reaction is one that results in a different arrangement of matter than you started with.

Examples of Chemical Properties

Flammability

Reactivity

Stability

Signs of a Chemical Change

There are four tell tale signs that a chemical change is occurring…

A release of a gas

A change of color

A release of heat and/or light

Formation of a precipitate

A Precipitate?

A precipitate is a solid that is produced from two solutions

Example: Pb(NO3)2 + KI Yellow

Precipitate

Solutions are samples where a substance is dissolved

into a liquid (typically water) and will have an (aq)

which stands for aqueous listed after their symbol.

States of Matter

How do we find matter around us in our environment?

The Physical States of Matter

Solid – Sample that has a definite volume and shape (particles locked in fixed position).

Liquid – Sample with definite volume, but it adopts the shape of any container (has fluid motion within sample).

Gas – Sample with neither a definite shape nor definite volume (particles have random, ceaseless, individual motion).

Phase Changes

Any time a sample changes from one state to another it is because the balance between particle energy and attractive forces between the particles has shifted

Phase Changes are Physical Changes!

Changes in Energy

You will see throughout the course that energy is involved in all changes, both chemical and physical changes

That means that changes in state are also displays of changes in energy.

Temperature measures the average energy of the particles in a sample

Enthalpy

the sum of the internal energy of a body or system (and the product of its volume multiplied by the pressure)

Phase Changes of Matter

More About Change

When a change occurs and energy is lost it is called exothermic…think of it this way: Exo Exiting the system

When a change occurs and energy is absorbed it is called endothermic…think of it this way: Endo Entering the system

Pure Substances

Are any materials with a fixed composition and definite physical and chemical properties

There two types of pure substances

Elements – unique arrangements of electrons, protons and neutrons that specific properties.

Compounds – two or more element chemically connected with definite composition and arrangements.

Classification of Matter

Types of Elements

Metals

Good conductor of heat and electricity

Malleable

Ductile

Lustrous/Shiny

High density

Most are solid at room temperature

Non-Metals

Poor conductors of heat and electricity

Dull

Brittle

Low density

Various physical states at room Temperature

Metalloids (aka semiconductors)

“Tweeners”

These elements have a combination of metal and non-metal properties.

Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium & Astatine are the only elements that fit this description

Silicon is the most commonly known

Mixtures

Are materials with two or more pure substances mixed together but not chemically connected to one another.

There are two types of mixtures Homogeneous – one phase with

uniform distribution of particles

Heterogeneous – clusters of atoms with two or more phases and a non-uniform distribution of particles.

Law of Conservation of Matter

States:

The amount of matter in the universe is constant

Matter cannot be created or destroyed only change form.