Chapter 2

Matter, Energy & Change

W/ Concept Mapping

Chapter Objectives

TSW be able to apply the skill of concept mapping as a means of organizing the classification of matter system.

TSW have a solid understanding of how our universe is composed of different arrangements & combinations of the known 113 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.

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 atoms.

Mass vs. Weight We use these terms interchangeably,

however, they do have different meanings when used correctly. Mass is defined as a measure of the

amount of matter in a sample. Weight is defined as a measure of the

pull of gravity on a sample of matter. Mass would remain constant

anywhere in the universe, however, the weight would change.

Atoms

An atom is the smallest portion of an element that retains the unique properties of that element. We will learn more about atoms

in the next chapter.

Pure Substances Are any materials with a fixed

composition having definite set of 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.

Examples Elements:

Na – sodium O2 – oxygen

Compounds: MgCl2 – Magnesium Chloride H2O – Water H2O2 – Hydrogen Peroxide

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.

Properties of Matter Every pure substance has a

definite set of physical and chemical properties that exist even in the smallest sized sample.

We can use these properties to identify a pure substance.

Chemical Property A Chemical Property is one that can

only be observed during the course 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 or absorption of heat and/or

light Formation of a precipitate

A Precipitate? A precipitate is a solid that is

produced from two liquid reactants.

Example: Pb(NO3)2 + KI Yellow Precipitate

Examples of Chemical Properties

Flammability Reactivity Stability

Chemical Changes A Change that results in a new

substance that has a different arrangement of atoms with a set of chemical and physical properties different from the substance we started with.

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.

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.

Density… Density is one of the most useful

intensive physical properties. 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 isD = mass / volume

Physical States of Matter Solid – Sample of matter that has a

definite volume and shape. Liquid – Sample of matter that has a

definite volume, but it adopts the shape of any container.

Gas – Sample of matter that has neither a definite shape nor definite volume.

Plasma – Sample of matter at high temperature where individual atoms lose their electrons.

Physical Changes These are changes in the

appearance of a substance, not in the identity of a sample of matter.

One example of this would be a change in the physical state that a sample of matter exists in. Example: Ice (solid water) melting

into liquid water.

Changes in State 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.

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

Law of Conservation of Matter States:

The amount of matter in the universe is constant

Matter cannot be created or destroyed only change form.