Pearson Prentice Hall Pearson Prentice Hall

Physical Science: Physical Science: Concepts in ActionConcepts in Action

Chapter 2Chapter 2

Properties of Properties of MatterMatter

2.1 Classifying Matter2.1 Classifying MatterObjectives:Objectives:1. Explain why elements and 1. Explain why elements and compounds are classified as pure compounds are classified as pure substancessubstances2. Distinguish mixtures and pure 2. Distinguish mixtures and pure substancessubstances3. Analyze the main difference 3. Analyze the main difference among solutions, suspensions & among solutions, suspensions & colloidscolloids

Definition: a pure substance is Definition: a pure substance is matter that always has exactly the matter that always has exactly the same compositionsame composition

Any particular pure substance Any particular pure substance always has the same properties always has the same properties because the substance has a fixed, because the substance has a fixed, uniform compositionuniform composition

Definition: an element is a Definition: an element is a substance that cannot be broken substance that cannot be broken down in simpler substancesdown in simpler substances

Elements as pure substancesElements as pure substancesElements contain only one type of atomElements contain only one type of atom

Elements have a fixed composition (due Elements have a fixed composition (due to only one type of atom)to only one type of atom)

Examples of elements: gold (Au), silver Examples of elements: gold (Au), silver (Ag) and platinum (Pt)(Ag) and platinum (Pt)

Names of elements have one or two Names of elements have one or two lettersletters

If there is a second letter, it is not If there is a second letter, it is not capitalizedcapitalizedhttp://www.chemicool.com/

Compounds as pure substancesCompounds as pure substancesDefinition: a compound is a substance Definition: a compound is a substance that is made from 2 or more simpler that is made from 2 or more simpler substances, AND can be broken down substances, AND can be broken down into simpler substancesinto simpler substancesA compound always contains 2 or more A compound always contains 2 or more elements joined in a fixed proportionelements joined in a fixed proportionSince compounds are matter that Since compounds are matter that always contain the exact same always contain the exact same elements in the exact same elements in the exact same proportions, they are pure substancesproportions, they are pure substances

Mixtures are not pure substancesMixtures are not pure substances

Recall that a pure substance is matter Recall that a pure substance is matter that always has exactly the same that always has exactly the same compositioncompositionMixtures vary in composition so they are Mixtures vary in composition so they are not purenot pureThe properties of a mixture can vary The properties of a mixture can vary because the composition of the mixture because the composition of the mixture is not fixedis not fixedExample: salsa- one batch may have Example: salsa- one batch may have more onions, fewer tomatoes or tons of more onions, fewer tomatoes or tons of peppers compared to another batchpeppers compared to another batch

Different types of mixturesDifferent types of mixturesDefinition: a heterogeneous mixture Definition: a heterogeneous mixture is not the same throughoutis not the same throughout

Example: fruit saladExample: fruit salad

Definition: a homogeneous mixture is Definition: a homogeneous mixture is the same throughoutthe same throughout

Example: rubbing alcohol or milkExample: rubbing alcohol or milk

Mixtures are also classified by the Mixtures are also classified by the size of the largest particles as size of the largest particles as solutions, suspensions or colloidssolutions, suspensions or colloids

Solutions, Suspensions & ColloidsSolutions, Suspensions & ColloidsDefinition: a solution is substances that Definition: a solution is substances that dissolve into each other to form a dissolve into each other to form a homogeneous solution (& do not separate homogeneous solution (& do not separate into layers)into layers)Definition: a suspension is a Definition: a suspension is a heterogeneous mixture that separates heterogeneous mixture that separates into layers over time such as sand & into layers over time such as sand & waterwaterDefinition: colloids are heterogeneous Definition: colloids are heterogeneous mixtures that are made of very tiny mixtures that are made of very tiny particles & some intermediate sized particles & some intermediate sized particles of pure substances disbursed in particles of pure substances disbursed in another substance that do not settle out another substance that do not settle out or separate such as gelatinor separate such as gelatin

Examples of physical Examples of physical propertiesproperties

Definition: a physical property is any Definition: a physical property is any characteristic of a material that can be characteristic of a material that can be observed or measured without changing observed or measured without changing the composition of the materialthe composition of the material

Here are some examples:Here are some examples:

Viscosity- resistance of a liquid to flowingViscosity- resistance of a liquid to flowing

Conductivity- ability of material to allow Conductivity- ability of material to allow heat to flowheat to flow

Malleability- ability of a solid to be Malleability- ability of a solid to be hammered without shatteringhammered without shattering

Hardness- resistance to scratchingHardness- resistance to scratching

Melting point- the temperature at Melting point- the temperature at which a substance changes form which a substance changes form solid to liquidsolid to liquid

Boiling point- the temperature at Boiling point- the temperature at which a substance boilswhich a substance boils

Density- the ratio of mass to volume Density- the ratio of mass to volume or m/vor m/v

2.2 Physical Properties2.2 Physical PropertiesObjectives:Objectives:1. Give examples of physical 1. Give examples of physical propertiesproperties2. Explain the usefulness of 2. Explain the usefulness of knowing physical propertiesknowing physical properties3. Describe how mixtures are 3. Describe how mixtures are separatedseparated4. Evaluate when a physical 4. Evaluate when a physical change has occurredchange has occurred

Usefulness of Physical PropertiesUsefulness of Physical PropertiesPhysical properties are used to Physical properties are used to identify a material, to choose a identify a material, to choose a material for a specific purpose or material for a specific purpose or to separate substances from a to separate substances from a mixturemixtureThe methods often involve math The methods often involve math since many physical properties since many physical properties are described by numbers are described by numbers (boiling point and melting point, (boiling point and melting point, for example)for example)

Separating MixturesSeparating MixturesThere are several waysThere are several ways

Here are some examples:Here are some examples:

Filtration- separating substances Filtration- separating substances based on the size of the particles based on the size of the particles (sand from water, for example)(sand from water, for example)

Distillation- separation of substances Distillation- separation of substances based on their boiling points based on their boiling points (requires that the boiling points are (requires that the boiling points are different from each other)different from each other)

Magnetism- using magnetic Magnetism- using magnetic property of some metals to property of some metals to separate from nonmagnetic separate from nonmagnetic materialsmaterials

Density- some substances may Density- some substances may float (less dense) in water, while float (less dense) in water, while others sink: using density this way others sink: using density this way allows separation of less dense allows separation of less dense substances from more dense substances from more dense substances such as driftwood substances such as driftwood floating on waterfloating on water

Recognizing Physical ChangesRecognizing Physical Changes

Definition: a physical change is a Definition: a physical change is a change in the physical form or change in the physical form or properties of a substance that properties of a substance that occurs without a change in occurs without a change in compositioncomposition

The substances in the material The substances in the material remain the sameremain the same

Size and shape might change but Size and shape might change but not compositionnot composition

Words that describe physical Words that describe physical changechange

Examples of physical change Examples of physical change include cutting, grinding, bending, include cutting, grinding, bending, water changing to steam, melting water changing to steam, melting of iceof ice

Some words that describe physical Some words that describe physical change: boil, freeze, dissolve, melt, change: boil, freeze, dissolve, melt, condense, break, split, crack, crush condense, break, split, crack, crush and dissolveand dissolve

2.3 Chemical Properties2.3 Chemical PropertiesObjectives:Objectives:1. Discuss when chemical 1. Discuss when chemical properties can be observedproperties can be observed2. Summarize which observations 2. Summarize which observations might indicate a chemical change might indicate a chemical change has occurredhas occurred3. Judge the difference between a 3. Judge the difference between a chemical and physical changechemical and physical change

Physical or Chemical?Physical or Chemical?

When matter undergoes a When matter undergoes a chemical change, the composition chemical change, the composition of the matter changesof the matter changes

When matter undergoes a When matter undergoes a physical change, the composition physical change, the composition of the matter remains the sameof the matter remains the same

Observing Chemical PropertiesObserving Chemical Properties

Definition: a chemical property is Definition: a chemical property is the ability to produce a change in the ability to produce a change in the composition of matterthe composition of matter

Chemical properties can be Chemical properties can be observed only when substances in observed only when substances in a sample of matter are changing a sample of matter are changing into different substancesinto different substances

Two types of chemical properties Two types of chemical properties include flammability and include flammability and reactivityreactivityDefinition: flammability is a Definition: flammability is a material’s ability to burn in the material’s ability to burn in the presence of oxygenpresence of oxygenDefinition: reactivity is the ability Definition: reactivity is the ability of a substance to combine of a substance to combine chemically with other substanceschemically with other substances

Observations of chemical Observations of chemical changechange

Change in color, production of Change in color, production of gas, formation of precipitategas, formation of precipitate

Definition: a precipitate is any Definition: a precipitate is any solid that forms when 2 liquids solid that forms when 2 liquids are mixedare mixed

Other examples of chemical Other examples of chemical change: Burn, rot, rust, change: Burn, rot, rust, decompose, ferment, explode and decompose, ferment, explode and corrodecorrode