Matter and Change

Chapter 2

Properties of Matter

Section 1

Why are bamboo chopsticks usually disposable?

What characteristic makes bamboo useful for cooking?

Describing Matter

Matter is anything that takes up space (volume) and has mass (amount of matter in an object).Previously defined as the general term for all materials or “stuff.”All matter can be described in terms of its properties.Properties used to describe matter can be classified as EXTENS IVE or INTENSIVE.

Extensive Physical Properties

Extensive properties are dependent upon the amount of material present.Examples include mass, length, and volume.

Intensive Physical Properties

Intensive physical properties DO NOT depend on the amount of material present; depends only on TYPE of matter.Examples include density, melting point, and boiling point.

Identifying Substances

Substances have a uniform and definite composition.All samples of a given substance have the same INTENSIVE properties because they have the same chemical composition.EXTENSIVE properties may vary because of the size of a sample.

Physical Properties

Physical properties can be either extensive or intensive.Physical properties are qualities or conditions of substances that can be observed or measured without changing the substance’s composition.Physical properties can help identify a substance.

States of Matter

There are four states of matter: solid, liquid, gas, and plasmaThe state of matter is dependent upon the pressure and temperature at which the matter existsThe state of matter is a PHYSICAL PROPERTY of the matter

Solids

Have a definite shape and volumeParticles are packed close together and vibrate weakly about fixed positionsNot compressibleParticles have low kinetic energy

Liquids

Have a definite volume, no definite shape and can flowParticles can move and slide Particles are very close together so liquids are practically non-compressibleParticles have more kinetic energy that solids

Gases

No definite shapeNo definite volumeParticles move rapidly in all directions; low attractive forces between particlesHigher kinetic energy than solid or liquidHighly compressibleVAPOR – describes the gaseous state of a material that is generally a liquid or solid at room temperature.

Plasma

Made up of ionized gas particlesMost abundant state of matter in the universeOccurs in stars, lightning bolts, fluorescent lightsTypically occur at temperatures over 5000 degrees C. at normal pressures

Comparing Solids, Liquids, and Gases

Physical Changes of Matter

Changes that DO NOT produce new substances.May change some physical properties, but the chemical composition of the substance remains the same.Physical changes can be reversible (boiling, freezing, melting) or irreversible (grinding, cutting, tearing).All changes in state are REVERSIBLE PHYSICAL changes.

Mixtures

Section 2

What is the result of panning?

What property is used to separate the mixture?

Classification of Matter

Mixtures

Physical combination of two or more types of matter.Most samples of matter are mixtures.Classified as HOMOGENEOUS or HETEROGENEOUS based on distribution of components.The number of PHASES (part of a sample with uniform composition) also determines type of mixture.Homogeneous – one phaseHeterogeneous – two or more phases

Homogeneous Mixtures

Homogeneous mixtures – combination of two or more kinds of matter with uniform compositionExamples include air, vinegar, salt water, and SpriteLiquid homogeneous mixtures are also called SOLUTIONSSolid homogeneous mixtures of metals are ALLOYS

Heterogeneous Mixtures

Heterogeneous mixtures – combination of two or more kinds of matter with different parts with different properties; composition is NOT uniformExamples include blood, whole milk, granite, and chocolate chip cookies

Separation Techniques

Differences in physical properties are used to separate mixtures.Technique chosen depends on mixture to be separated.

DistillationChromatographyDensityCentrifugeFiltration

Elements and Compounds

Section 3

What are the properties of cotton candy?

Why does it taste sweet?

Can only be broken down by chemical methods

Separated by physical processes

Cannot be separated into simpler substances by ordinary chemical methods.

Distinguishing Elements and Compounds

ELEMENTSSimplest form of matter with unique propertiesCannot be broken down by ordinary chemical meansListed on the periodic table

COMPOUNDSTwo or more elements chemically combinedBroken down into simpler substances by chemical methodsDifferent properties than elements from which they form

Substances can be classified as ELEMENTS or Substances can be classified as ELEMENTS or COMPOUNDSCOMPOUNDS

Elements

Simplest type of matter made up of only one type of atomsElements arranged according to increasing atomic number and recurring properties in PERIODIC TABLE OF THE ELEMENTSPeriodic table created by Mendeleev, refined by Mosely and SeaborgEach element has unique one or two letter symbol

Compounds

Chemical combinations of two or more elementsMost familiar substances are compoundsLaw of Definite Composition applies to compounds

COMPOUNDS CAN BE BROKEN DOWN INTO SIMPLER SUBSTANCES BY

CHEMICAL MEANS, BUT ELEMENTS CANNOT.

IF THE COMPOSITION OF A MATERIAL IS FIXED, THE MATERIAL IS A SUBSTANCE. IF THE COMPOSITION OF A MATERIAL MAY VARY, THE MATERIAL IS A MIXTURE.

Symbols and Formulas

Chemical symbols are used to represent elements.

One or two letter designation1st letter always capital; 2nd letter lowercase

Chemical formulas are used to represent compounds.

Shorthand way to show composition of compoundSubscripts indicate relative proportions of elements in compound

Chemical Reactions

Section 4

What evidence do you see in this photo that a chemical change has occurred?

Chemical Changes

Chemical properties describe the ABILITY of a substance to undergo a chemical change.During a CHEMICAL CHANGE, a new substance with new and different properties is produced; the composition of the matter always changes.Also called a CHEMICAL REACTION.During a chemical reactions, one or more substances changes into one or more new substances.

REACTANTS PRODUCTS

Recognizing Chemical Changes

Possible clues to chemical change include a transfer of energy, a change in color, the production of a gas, or the formation of a precipitate.Energy – heat given off (exothermic) or taken in (endothermic).Color – indicators; new substances.Gas – bubbles of insoluble gas released.Precipitate – an insoluble solid product that forms during a reactions.CAREFUL – some of these indicators may be present during physical changes; only analysis of reactant and product can definitively prove a reaction has occurred.

Conservation of Mass

During any chemical reaction, the mass of the products is always equal to the mass of the reactants.Mass also holds constant during physical changes.Mass is neither created nor destroyed.

Figure 2.12 from page 55.