Matter and Matter and ChangeChange

Chemistry is…

…the study of the composition, structure, and properties of matter and the changes it undergoes

MatteMatterr

Anything that has mass and occupies space

MasMasssA measure of the amount of matter

WeightThe measure of the force of gravity acting on an object

AtomAtom

The smallest unit of an element that maintainsthe properties of that element

By asking questions scientists can classify matter into:

• Mixtures – two or more substances that are not chemically combined with each other

• and can be separated by physical means. The substances in a mixture retain their individual properties.– Solutions – a special kind of mixture

where one substance dissolves in another.

• Elements – simplest form of pure substance. They cannot be broken into anything else by physical or chemical means.

• Compounds – pure substances that are the unions of two or more elements. They can be broken into simpler substances by chemical means.

Types of Chemical Formulas• An empirical formula gives the relative number of atoms of each element in a compound; i.e., the smallest whole number ratio that is possible.• A molecular formula gives the actual number of atoms of each element in a molecule of a compound. Molecular EmpiricalHydrogen peroxide H2O2 HOWater H2O H2OGlucose C6H12O6 CH2O• A structural formula uses lines to representcovalent bonds, and shows how the atoms in amolecule are joined together:H—O—O—H H—O—H O=C=O

Homogeneous – a substance that is the same throughout.

Heterogeneous – a substance that is different throughout.

Separation of a CompoundSeparation of a CompoundThe Electrolysis of water

Water Hydrogen + Oxygen

H2O H2 + O2

Reactant Products

Compounds must be separated by chemical means.With the application of electricity, water can be separated into its elements

Separation of a MixtureSeparation of a Mixture

Distillation

Properties of Properties of MatterMatterExtensive propertiesExtensive properties

Intensive propertiesIntensive properties

Volume Mass

depend on the amount of matter that is present.

do not depend on the amount of matter present.

Melting pointBoiling point Density

Physical Physical ChangeChangeA change in a substance that does not involve a change in the identity of the substance.

Example:A change in size, shape color etc.

Phase Changes

Phase Phase DifferencesDifferences

SolidSolid – definite volume and shape; particles packed in fixed positions.LiquidLiquid – definite volume but indefinite shape; particles close together but not in fixed positions

GasGas – neither definite volume nor definite shape; particles are at great distances from

one another Plasma – high temperature, ionized phase of matter as

found on the sun.

Phase changes occur when a substance changes state from…

A solid to liquid…melting

A liquid to solid…freezing

A liquid to gas…boiling

A gas to liquid…condensing

A solid to gas…subliming

A gas to a solid…deposition

The heat that is being added to a given state that does not result in a temperature increase is being used to overcome the intermolecular forces between the particles.

The heat added to a solid to convert it to a liquid is called the heat of fusion. (fusion means melting)

You add heat to get a solid to melt. When you condense a liquid back to a solid, you get that heat back!

Melting and freezing are only different in which way heat flows in or out of a substance.

The same occurs at the boiling/condensation point. The heat put in to a liquid to convert it to a gas is called the heat of vaporization.

When a gas is condensed to a liquid, then that heat is again released.

Boiling and condensation are only different in the direction of heat flow in or out of a substance.

Copper Phases - SolidCopper Phases - Solid

Copper Phases - LiquidCopper Phases - Liquid

Copper Phases – Vapor (gas)Copper Phases – Vapor (gas)

Chemical Chemical ChangeChange

A change in which one or more substances are converted into different substances. Something new is created.

Heat and light are often evidence of a chemical change.

Catalyst – a substance that increases the rate of a chemical

reaction without itself being permanently changed.

Entropy – the measure of disorder in a substance.

Physical propertiesshape size

texture hardnessodor masscolor state

freezing point magnetism melting point

More physical properties

• conductivity (conducts electricity)malleability (can be hammered into sheets)ductility (can be drawn into wires)solubility (will dissolve in another substance)density (mass / volume)

Chemical properties

•Flammibilty•Reactivity•Combustibility•Acidic or basic

Properties of MetalsProperties of Metals

Metals are good conductors of heat and electricity

Metals are malleable

Metals are ductile

Metals have high tensile strength

Metals have luster

Examples of MetalsExamples of Metals

Potassium, K reacts with water and must be stored in kerosene Mercury, Hg, is the

only metal that exists as a liquid at room temperature

PropertiesProperties of Nonmetalsof Nonmetals

Carbon, the graphite in “pencil lead” is a great example of a nonmetallic element.

Nonmetals are poor conductors of heat and electricity Nonmetals tend to be brittle Many nonmetals are gases at room temperature

Examples of NonmetalsExamples of Nonmetals

Sulfur, S, was once known as “brimstone”Graphite is not the only pure form of carbon, C. Diamond is also carbon; the color comes from impurities caught within the crystal structure

Properties of MetalloidsProperties of MetalloidsMetalloids straddle the stairstep. They have

properties of both metals and nonmetals.

Metalloids are more brittle than metals, less brittle than most nonmetallic solids Metalloids are semiconductors of electricity Some metalloids possess metallic luster

Silicon, Si – A MetalloidSilicon, Si – A Metalloid

Silicon has metallic luster Silicon is brittle like a nonmetal Silicon is a semiconductor of electricity

Number of naturally occuring elements is 90

Sir ramsey discovered the Noble gases, octets, group 8, helium family

Accuracy – nearness of a measurement to its accepted value

Precision – agreement between numerical values of a set of measurements.