Matter Notes Note :Slide 1-38 (Packet 1 ) , Slide 39-49 (Packet 2) Chemistry Ch 3

The Nature of Matter Gold Mercury Chemists are interested in the nature of matter and how this is related to its atoms and molecules.

Chemistry & Matter We can explore the MACROSCOPIC world — what we can see — to understand the PARTICULATE worlds we cannot see. We write SYMBOLS to describe these worlds.

A Chemist’s View of Water Macroscopic H2O (gas, liquid, solid) Symbolic Particulate

A Chemist’s View Macroscopic 2 H2(g) + O2 (g) --> 2 H2O(g) Particulate Symbolic

Kinetic Nature of Matter Matter consists of atoms and molecules in motion.

STATES OF MATTER SOLIDS — have rigid shape, fixed volume. External shape can reflect the atomic and molecular arrangement. Reasonably well understood. LIQUIDS — have no fixed shape and may not fill a container completely. Not well understood. GASES — expand to fill their container. Good theoretical understanding.

OTHER STATES OF MATTER PLASMA — an electrically charged gas; Example: the sun or any other star

Physical Properties of Matter

STATES OF MATTER: SOLIDS Particles of solids are tightly packed, vibrating about a fixed position. Solids have a definite shape and a definite volume. Heat

STATES OF MATTER LIQUID Particles of liquids are tightly packed, but are far enough apart to slide over one another. Liquids have an indefinite shape and a definite volume. Heat

STATES OF MATTER GAS Particles of gases are very far apart and move freely. Gases have an indefinite shape and an indefinite volume. Heat

The phase change from a solid to liquid is called melting.

17. Describe how taking a shower is an example of condensation.

18. The phase change from a liquid back to a solid is called Freezing

19. Dry ice turning directly into a gas is an example of what kind of phase change? (solid gas) sublimation

Gas – Solid

Phase Change

Physical Properties What are some physical properties? color melting and boiling point odor

Physical properties of matter are categorized as either Intensive or Extensive: Intensive - Properties that do not depend on the amount of the matter present. Color Odor Luster - How shiny a substance is. Malleability - The ability of a substance to be beaten into thin sheets. Ductility - The ability of a substance to be drawn into thin wires. Conductivity - The ability of a substance to allow the flow of energy or electricity. Hardness - How easily a substance can be scratched. Melting/Freezing Point - The temperature at which the solid and liquid phases of a substance are in equilibrium at atmospheric pressure. Boiling Point - The temperature at which the vapor pressure of a liquid is equal to the pressure on the liquid (generally atmospheric pressure). Density - The mass of a substance divided by its volume

Physical properties of matter are categorized as either Intensive or Extensive: Extensive - Properties that do depend on the amount of matter present. Mass - A measurement of the amount of matter in a object (grams). Weight - A measurement of the gravitational force of attraction of the earth acting on an object. Volume - A measurement of the amount of space a substance occupies. Length

Physical Changes Some physical changes would be boiling of a liquid can be observed without changing the identity of the substance Some physical changes would be boiling of a liquid melting of a solid dissolving a solid in a liquid to give a homogeneous mixture — a SOLUTION.

Chemical Properties and Chemical Change Burning hydrogen (H2) in oxygen (O2) gives H2O. Chemical change or chemical reaction — transformation of one or more atoms or molecules into one or more different molecules.

Sure Signs of a Chemical Change Heat Light Gas Produced (not from boiling!) Precipitate – a solid formed by mixing two liquids together

Physical vs. Chemical physical Examples: melting point chemical flammable density magnetic tarnishes in air

Physical vs. Chemical chemical Examples: rusting iron physical dissolving in water burning a log melting ice grinding spices

Can it be physically separated? Matter Flowchart MATTER yes no Can it be physically separated? MIXTURE PURE SUBSTANCE Is the composition uniform? no yes Can it be chemically decomposed? no yes Homogeneous Mixture (solution) Heterogeneous Mixture Compound Element Colloids Suspensions

Types of Mixtures Variable combination of 2 or more pure substances. Heterogeneous – visibly separate phases Homogeneous – Same throughout

Law of Definite Proportions Joseph Proust (France 1799) A given compound always contains elements in a certain proportion by mass. (Constant composition).

Percent Mass of Compounds Atoms combine in whole number ratios, so their proportion by mass will always be the same. Example: H2O is always made up of 2 atoms of H and one atom of O. The mass ratio of O to H in water is always 16:2 or 8:1. Percent Mass of Compounds Percent composition consists of the mass percent of each element in a compound: Percent by mass=

Example: KCl KCl always contains one atom of K for every one atom of Cl In KCl, potassium and chlorine always have a ratio of “39.09 to 35.45” or “1.1 to 1” by mass.

Law of Multiple Proportions (John Dalton) When the same two elements combine to form more than one compound: the ratios of the mass of one element in the first compound to its mass in the second compound, (as it combines with the same mass of the other element), can always be expressed as ratios of small whole numbers( ex: 1:3 or 2:5).

Example of Law of Multiple Proportions Carbon combines with oxygen to form CO and CO2 . Mass of Carbon(g) Mass of Oxygen(g) Ratio of O in CO2 to O in CO CO CO2 12.01 16.00 2:1 12.01 32.00

Practice Problem 1 In the carbon compounds ethane (C2H6) and ethene (C2H4), what is the lowest whole number ratio of H atoms that react with the same number of C atoms? Mass of Carbon (g) Mass of Hydrogen (g) Ratio of H in C2H6 to H in C2H4 C2H6 C2H4 24.02 6.06 6:4 or 3:2 24.02 4.04

Mixtures Heterogeneous mixture – Uneven distribution of substances. You can see the different parts. Examples: Sand Granite Wood Suspensions

Mixtures Homogeneous Mixture – Components are evenly mixed. - Cannot see the parts. Salt water contains salt and water, but are mixed all the way to the atomic level but it can still be separated by physical means.

Homogeneous Solutions Solute dissolves in solvent to form solution. Concentrated solution contains more solute than dilute solution. Small particle size (<2nm) Can NOT be separated by filtration Ex: Kool-Aid, iced tea, coffee

Solutions A solution is a homogeneous mixture A solute is the substance being dissolved A solvent is dissolving the solute, most commonly a liquid (H2O) Called an aqueous (aq) solution when solvent is H2O Typically, the solute is the component in the smaller amount. Solvent is the component in the larger amount. 42

Types of Solutions Solution of gaseous solute in gaseous solvent: Air (Oxygen & Nitrogen) Solution of gas in liquid: Soft drinks (CO2 in water). Solution of liquid in liquid: Nail polish remover (acetone in water) Solution of solid in liquid: Salt in water Solution of solid in solid: Alloys such as steel (a mixture of Fe & C).

Separation Methods: Filtration Distillation Crystallization Sublimation Chromatography

Filtration Used to separate heterogeneous mixtures composed of solids & liquids Uses a porous barrier (such as filter paper) that allows the liquid to pass through, but no the solid Example: sand and water mixture

Distillation Used to separate homogeneous mixtures Based on the differences in the boiling points of the involved substances Mixture is heated until the substance with the lower boiling point boils to a vapor The vapor is then condensed into a liquid and collected Example: distilled water (removes minerals from the water)

Crystallization Used to separate substances in solution Results in the formation of highly pure solids As one substance evaporates, the dissolved substance comes out of solution and collects as crystals Example: rock candy, salt water

Sublimation Used to separate mixtures of solids One solid sublimes and the other is left behind The gas can then be condensed and collected Example: separating ammonium chloride (NH4Cl) from sand and salt

Chromatography Used to separate components that are dissolved in a liquid or a gas Based on the ability of each component to be drawn across the surface of another material When the mixture is a liquid, it is drawn across chromatography paper Separation occurs because the various components travel across the paper at different rates (the stronger attraction to the paper, the slower the rate) Example: forensics: blood levels of toxins after a person’s death

What is a property? Describes a substance (matter) Can be measured and/or observed Some can be used to identify a substance Chemical property Physical property observed during a describes matter reaction

Intensive Properties of Pure Substances remain the same when a substance changes in size Some can be used to IDENTIFY a pure substance (density, boiling pt., melting pt.) Apple floation demo (density) Burn paper of different sizes Fork vs. paperclip in outlet

Intensive Properties If you can find it on a chart, it’s intensive

Extensive Properties of Pure Substances Properties that are dependent on the amount of substance present (can be measured) Can’t be used to identify Mass, volume, & length

-depend on identity of substance -depend on amount of substance Properties Intensive -depend on identity of substance Extensive -depend on amount of substance Physical Physical Phase/state Density Luster Malleability Melting Pt. Boiling Pt. Conductivity Brittleness Specific Heat Capacity Mass Volume Length Weight

Physical Properties Phase (state of matter): solid, liquid, gas, plasma Luster: shiny Malleable: can be pounded into sheets

Physical Properties… Conductive: Ability to transfer thermal energy or electricity Ductile: drawn into wire (metals) Viscosity: resistance of a liquid to flow

Physical Properties… Brittle: ability to break Volatile: tendency for a substance to vaporize at normal (room) temperatures Nonvolatile: doesn’t vaporize at normal (room) temperatures

Physical Properties that can identify a substance… Density (D): relationship between the mass of a substance and how much space it takes up. (Does it sink or float in H2O?) Specific Heat Capacity (C): Amount of heat required to raise 1 g of water 1°C

Physical Properties that can identify a substance… Melting Point/Freezing Point: temperature at which a substance melts & freezes Boiling Point/Condensation Point: temperature at which a substance boils & condenses

Physical Properties that are extensive… Mass: how much matter in a substance (g or kg) Volume: how much space the substance occupies (mL, L, cm3) Length: how long something is (cm, m, km)

Chemical Properties Number of valence e- - determines if & how a substance will react Reactivity – tendency of a substance to react chemically

Chemical Properties… Flammability – how easily a substance ignites or catches fire. Combustibility – ability of a substance to burn. Toxicity – ability of a substance to harm a living organism (humans)

Physical & Chemical Changes All physical & chemical changes require ENERGY!

Physical Change Physical Change – a change in the appearance of a substance but does NOT change its composition Substances can be physically mixed together, but retain their own properties Nitrogen gas (N2) Oxygen gas (O2) Mixture of gases (N2+O2) + = Not sure if you want to go into this much detail

Ex. 1. Phase changes 2. Making a mixture Melting, boiling, sublimation sublimation of I2 Freezing, condensing, deposition 2. Making a mixture

Chemical Change Formation of a new substance with different properties that are observed Substances chemically react & products have different properties than reactants. Hydrogen gas (H2) Oxygen gas (O2) Water (H2O) + =

Chemical Change Formation of a new substance with different properties that are observed Evidence of a Chemical Change: 1. Change in temperature 2. Production of a gas

3. Permanent color change when a new substance is made 4. Precipitate – formation of a solid product from 2 aqueous solutions reacting

Chemical Change Examples Corrosion: breaking down of a metal through a chemical reaction 1. Rusting: reddish orange layer of corrosion over Fe 2. Tarnishing: black layer of corrosion over Cu, Ag, Al, Mg, etc. Fermenting: converting of carbs to alcohols or acids using microorganisms Photosynthesis

Physical & Chemical Changes Can Occur Simultaneously Burning a candle Eating candy Weathering in nature Combustion of wood Have students discuss what the 2 types of changes are in each burning of wood. The moisture present in the wood turns to vapor, when heated, which is a physical change. The actual burning of wood will generate carbon dioxide (among other products) and is a chemical change. 

Is melting ice a physical or chemical change? Before After Properties Before: Properties After: Worksheet ex. Are these properties intensive or extensive? Is the composition changing?

Are exploding fireworks a physical or chemical change? Before After Properties Before: Properties After: Worksheet ex. Are these properties intensive or extensive? Is the composition changing?

Ability to tarnish with air Identify the following as either a physical property, a chemical property, a physical change, or a chemical change. Water vaporizing An old bike rusts Has luster Conducts electricity Ability to explode Photosynthesis Crushing a soda can Ability to tarnish with air Physical change Chemical change Physical property Physical property Chemical property Worksheet ex. Chemical change Physical change Chemical property