Matter and Change

Chapter 2

Properties of Matter

Matter has many different properties These properties can be used to classify and

identify various forms of matter Properties used to describe matter can be

classified as extensive or intensive

Extensive & Intensive Properties

Extensive properties Depend on amount of matter present Examples: ?

Intensive properties Depend on type of matter Do not depend on amount of matter present Examples: ?

Identifying Substances

A substance is matter that has a uniform and definite composition

Any given substance will have a unique set of intensive properties

These properties can be used to identify or separate the substance from other substances.

Problem: How could you separate a mixture of iron filings from sugar?

Physical Properties

Can be observed or measured without changing the identity of the substance

States of Matter: Solids

Solids Definite shape Definite volume Particles fixed in

place

States of Matter: Liquids

Liquids Definite volume Indefinite Shape Particles can move

past each other

States of Matter: Gases

Gases Indefinite shape Indefinite volume Easily compressed Particles very far

apart Particles moving

rapidly

Vapors and Gases

Gases are substances that are normally in a gaseous state at room temperature Examples: O2, N2, He

Vapors are substances in a gaseous state that are normally solid or liquid at room temperature

H2O (l) + heat H2O (g)

Physical Changes

Changes to a substance that do not involve a change in composition

Reversible or irreversible Melting Freezing Stretching Chopping Grinding

2.2 Mixtures

A physical blend of two or more substances Types of mixtures Homogeneous

Composition is uniform Consists of a single phase

Heterogeneous Composition is not uniform throughout Have two or more phases

Phases of a Mixture

Some heterogeneous mixtures have homogeneous regions called phases

Separating Mixtures

Use different physical properties of substances to separate components

Some techniques include…. Filtration Chromatography

Many types Distillation

Distillation

Liquids can be separated by boiling point

2.3 Elements & Compounds

An element is the simplest form of matter that has a unique set of properties. Contains only one type of atom C, H, O, He, Ag, Na, K, etc. Periodic Table contains all known

elements

Elements & Compounds

A compound is a substance that contains two or more elements chemically bonded in a fixed proportion. Contains two or more different types of

atoms H2O water C6H6 benzene Ca(OH)2 calcium hydroxide C2H4O2 acetic acid

Elements are the simplest form of matter

Elements cannot be broken down into simpler substances

Compounds can C6H12O6 → __ C + __ H2O

C6H12O6 → 6 C + 6 H2O

Properties of Compounds

Usually quite different than the properties of the elements making up the compound

Different compounds have different physical and chemical properties

Stop and think…….

In chemistry, what is a particle?

Is a compound a mixture? Why or why not?

2.3Classifying Matter

Symbols & Formulas

Elements are represented by symbols Compounds are represented by formulas Interpreting chemical formulas

Subscripts indicate the number of atoms HNO3

Na2O

C12H22O11

Compounds have a constant chemical composition

2.4 Chemical Reactions

Chemical property Tendency to undergo a specific type of chemical

change E.g. acids donate protons HCl + NaOH → NaCl + H2O

Chemical changes Involve a change in chemical composition Atoms are rearranged to form new substances HCl + NaOH → NaCl + H2O

Chemical Reactions

Common terms that suggest chemical change Rot, ferment, corrode, rust, burn, decompose, etc.

Process of chemical change Reactants → Products

HCl + NaOH → NaCl + H2O Fe + S → FeS C3H8 + 5O2 → 3CO2 + 4H2O

Recognizing Chemical Change: Evidence?

Energy transfer Color change Formation of a gas

HCl + NaHCO3 → NaCl + H2O + CO2 (g)

Formation of a precipitate An insoluble solid product CaCl2 (aq) + NaOH (aq) → Ca(OH)2(s) + NaCl (aq)

Law of Conservation of Mass

During chemical reactions matter is neither created or destroyed

Mass of reactants = mass of productions 50 g + 25 g → 65 g + 10 g Beginning mass = ending mass