Read the Introduction to Chapter 1, and Sections 1.7 and 1.8 of the textbook before viewing this slide show.

Unit 3 Matter and Its Transformations What is chemistry? (Introduction to Chapter 1) Physical and chemical properties (1.7) Physical and chemical changes (1.7) Classification of matter (1.8)

What is Chemistry? (Intro to Chapter 1) Matter – anything that occupies space and has a mass (1.7) Chemistry – the study of matter and its transformations (Introduction to Chapter 1)

Physical Properties (1.7) Physical property – a physical characteristic or behavior of the material –Examples: boiling point, hardness, color –To get a feel for physical properties, you might want to go to this link Click on any of the elements in the periodic table and then click on the Physical button in the left menu You will see what are primarily physical properties listed for that element (I am not sure cost is one, but it is at least interesting.)

Chemical Properties (1.7) Chemical property – describes how the material reacts with (or doesn’t react with) with other types of matter –Examples: iron rusts in moist air, hydrogen and oxygen react violently to form water, neon does not react with much of anything –To get a feel for chemical properties, you might want to go to this link Click on any of the elements in the periodic table and then click on the Media button in the left menu You will see under the Video heading short film clips of reactions the material undergoes with various other materials. Its interaction (or noninteraction) with other materials is a chemical property.

Physical and Chemical Changes (1.7) Physical change – a change in the appearance of a substance without changing its chemical identity or composition –Examples: melting ice, cutting a piece of wood in half Chemical change – a change in the chemical identity of matter into other substances that are different –Examples: hydrogen and oxygen react to form water, a piece of iron rusts –The video clips mentioned on the previous slide are examples of materials undergoing a chemical change.

Classification of Matter (1.8) With over 18 million characterized compounds, classification is important to provide a framework for study This initial classification system provides a good starting point As you might imagine, there are subclassifications under many of these basic groupings

States of Matter (1.8) Three common states of matter (plus a bonus): –Gas – takes shape of container, flows easily, compressible –Liquid – takes shape of container but with a flat top, flows easily, not very compressible –Solid – retains shape, does not flow appreciably, not very compressible –(A bonus state: plasma – a stream of charged particles – this is the stuff of plasma TV)

Particle Level Description of States of Matter Gas: Particles “far” apart Particles moving rapidly Liquid: Particles “close” together Particles moving slowly Particles more ordered than gas, but not as much as solid Solid: Particles “close” together Particles vibrating but not changing location Particles very ordered Images are screen shots from States of Matter simulation PhET Interactive Simulations University of Colorado Notice that as the temperature decreases the particles get closer together and move more slowly

Pure Substances and Compounds (1.8) Pure substance – has a definite fixed composition that does not vary from one sample to another –Examples: pure copper, pure water Mixture – variable composition that can be different from one sample to another –Examples: salt water, air, sand and water mixed together

Further Classification of Pure Substances Pure substances can further be categorized as: –Elements – substances which cannot be broken down into simpler substances by chemical means –Compounds – chemical combination of two or more elements

Periodic table from common.wikimedia.orgcommon.wikimedia.org Periodic Table – the elements A sample periodic table - if it’s a known element it is on here. Compounds are chemical combinations of multiple elements. A large portion of our course will be involved with studying the periodic chart.

Further Classification of Mixtures Mixtures can further be categorized as: –Homogeneous – all parts of the mixture have the same composition and appearance Examples: sugar dissolved in water, air, a “pinch” of salt dissolved in water –Heterogeneous – appearance is not the same throughout Examples: sand in water, oil in water

An Early Atomic View (1.7) Some of these terms become a little clearer if we consider them on a microscopic scale. We will look at atoms in considerable detail soon but for now let’s take a simplistic view. An atom is the basic building block of matter. The elements of the periodic chart are composed of atoms.

An Early Atomic View (cont.) (1.7) Atoms of different elements are different. Molecules are formed when atoms chemically unite, or bond. If a molecule consists of all of one kind of atom, it is an element. If a molecule has two or more different elements in it, it is a compound.

An Early Atomic View (cont.) (1.7) Consider a hydrogen molecule which can be represented by H-H. An oxygen molecule can be represented by O-O. Hydrogen is flammable, oxygen supports combustion. If a balloon is filled with hydrogen and oxygen gas it could be filled to any ratio we wanted – example 2:1, 5:3, 1:8, etc.

An Early Atomic View (cont.) (1.7) If we hold a match to the balloon, it will explode. In the process, water which may be represented by H-O-H is formed. The elements H-H and O-O reacted to form the compound H-O-H. Notice that H-H is flammable, O-O is combustible, but H-O-H is used to put out fires. Compounds have different properties than the elements from which they are made.

Summary of Classification of Matter Matter Pure Substances ElementsCompoundsMixtures Homogeneous Mixtures Heterogeneous Mixtures

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