Physical-Chemical Properties

Mixtures/Elements/Cmpds

Adapted from “Matter, Building Block of the Universe” Prentice Hall

Made by Jim Barnaby 2004

Matter

Matter

Anything with mass and volume

Physical Properties

Physical Properties

Physical Properties describe objects (matter) and are used to identify and compare different types of matter

Color, odor, size, shape, state (phase), texture, hardness, taste, density, boiling point, melting point, freezing point, magnetism, conductivity, conducts heat, mass, weight, volume, solubility …

Physical Change

Physical Change

Change in size, state or shape or changes in other physical properties. One or more physical attributes transform, but the chemical identity is unchanged.

Differentiate gases

Suppose you have to distinguish between two gases, Oxygen and Hydrogen (O2 & H2). Both are colorless, tasteless and odorless. Since they are gases they have no definite volume. Each has a specific density but you cannot determine volume to get density.

Describe a brief procedure you can use to differentiate between the two gases (O2 & H2).

Chemical Properties

Chemical Properties

The properties that describe how a substance changes into other new substances.

The tendency of a substance to change chemical identity (transforms into a different substance)

Chemical property-change

A Chemical Property describes a substance’s ability to change into a different substance, a Chemical Change is the process by which the substance changes.

 

(Example, the ability of a substance to burn is a chemical property, the process of burning is a chemical change)

Chemical Reaction

Chemical Change (Chemical Reaction)New substances with different properties are formed

A substance changes its chemical identity, atoms are re-arranged to produce a new substance with different properties

 Chemical ReactionNew substance is formed by the re-arrangement of atoms

Evidence of Chemical Change

Evidence of chemical change

Color change, rust, exothermic (hot-produces heat energy), endothermic (cold-absorbs heat energy), light, bubbles, burning, explosion (releases energy), flammability—ability to burn

Physical or Chemical Change?

The main difference between a physical and a chemical change is that a chemical change involves the production of a new substance. Physical changes are easily reversed.

Physical or Chemical

Physical or Chemical change

Light a match

Slice a cake into 4 pieces

Ice cream melts into mush

Alka-seltzer in water

Crumple a piece of Al foil

Baking soda and vinegar

Physical or Chemical

Water freezes into ice

Water boils

Jeans fade in the sun

Bleach clothes

Digest food

A candle melts

 List physical properties for clock, table, person, …..etc

Demos—Labs

Demonstrations:

 Roast marshmallows—C12H22O11

draw rxn on the board

Complete and turn in metal salts flame lab

Investigate aquarium experiment

Deep rock jug

Grocery Store

How is a grocery store (supermarket) set up?

Produce, meats, dairy, frozen foods, drinks, …etc

 Imagine how hard it would be to find items if there were no organized way of groceries in a grocery store.

Frozen pizza next to panty hose…

Classification of matter

According to makeup, matter is classified into (4 classes):

Matter exists as:

Mixtures

Solutions

Elements

Compounds

Mixture

MixtureMatter that consists of two or more

substances mixed together but not chemically combined.

The substances keep their separate identities and most of their own properties, however their chemical composition does not change.

 2 types of mixtures are heterogeneous and homogeneous mixtures

Heterogeneous Mixture

Heterogeneous mixtureLeast mixed mixture does not appear to be the same throughout. Parts are easy to recognize and separate. Examples: granite, tacos, bowl of cereal, big Mac, Italian salad dressing, concrete, crunchy peanut butter, sandwich….

Homogeneous Mixture

Homogeneous mixture

Well-mixed, appears to be the same throughout. Particles are small, not easily recognizable and do not settle when the mixture is allowed to stand.

Examples: air, milk, glass, stainless steel, kool aid…

Colloids

ColloidsHomogeneous mixtures where the particles are mixed together but not dissolved. The particles in a colloid are relatively large in size and are kept permanently suspended. Colloids do separate on standing as do many heterogeneous mixtures.Examples: milk, whipped cream, toothpaste, suntan lotion…

Solution

Solution

Type of homogeneous mixture formed when one substance is dissolved in another. “Best mixed” of all mixtures. Particles are evenly spread out.

Examples: soda pop, lemonade, kool aid, tea

Solute – substance that is dissolved

Solvent – substance that does the dissolving

Properties of solutions

See chart on word document

Solutions can exist in any of the three phases: solid, liquid or gas.

 

Property of solution is that particles are evenly spread out (dissolved)

Solubility

SolubilityAmount of solute that can be completely

dissolved in a given amount of solvent at a specific temperature.

How can you increase the solubility of a substance?

Increase temp-increase solubility (add heat energy)Increase agitation-increase solubilityDecrease temp-decrease solubility

Soluble/Insoluble

A substance that dissolves in another substance is soluble in that substance.

(sugar is soluble in water)

Insoluble does not dissolve (sand in water)

Alloys

Alloys

Metal solutions

Solids dissolved in solids.

Gold jewelry is a solid solution of Au and Cu

Brass is an alloy of Cu and Zn

Sterling silver is an alloy of Ag and Cu

Stainless steel is an alloy Cr and Fe

Pure Substances

Pure substances

Matter that cannot be separated by physical means (elements and compounds)

 Element

Substance that contains only 1 type of atom

Examples: H, He, O, B … anything from periodic table

Compounds

Compound

Substance formed when different types of atoms bond with one another

Composed of 2 or more atoms bonded together

Examples: NaCl, C12H22O11, NaOH,

AgCl

Compounds differ

Chemical compounds are uniquely different from the elements that make them up. Sodium and chloride are extremely toxic by themselves, however sodium chloride is necessary for good health.

Molecule

Molecule

2 or more atoms bonded together. Smallest particle of a compound that has all the properties of that compound.

Examples: H2O NaCl

Sketch molecules on board

Elements, compounds, mixtures

See word document for chart

Sketch matter flow chart on board (This is on study guide to save copy time)

Classify list from word document (do orally)

Separate mixtures

Explain how you could use physical properties to separate the following mixtures:

Sand-saltOil-waterSalt-waterRubbing alcohol-waterSawdust-sandGold-sandIron filings-sulfur

Atoms

Atom

Smallest particle of an element that has all the physical and chemical properties of that element

Basic building block of all matter

Atoms are mostly empty space (analogies)

Chemical Symbol

Chemical Symbol

Shorthand way to represent an element

Single letter or first letter is always capitalized

Second letter is always lower case

As, Fe, Se, He, Ar, ….

Chemical Formula

Elemental (Chemical) formula

Combination of chemical symbols to represent a substance’s identity

Atomic symbol along with a numerical subscript to indicate the number of atoms grouped together

Chemical formulas

O2 - 2 - O atoms

O3 - 3 – O atoms

S8 - 8 – S atoms

4 O2 - 4 – O2 molecules -

8 – O atoms

NaCl, Fe2O3, KCl

Applied Chemical Formulas

List the element and the number of atoms for each element

NaHCO3

C12H22O11

3 H2SO4

5 CaCO3

Remember

Remember—chemical compounds are uniquely different from the elements from which they are made.Na+ - toxic – explosive in waterCl- - toxic – green gas, death in less than 1.5 secondsNaCl – table salt—sodium chloride—essential for good health

The “real” world

In nature, it is rare that elements or compounds are found in a purified state. We find them “mixed together” in mixtures, which can be separated by differences in physical properties.

Chemical Equation

Chemical Equation

Description of a chemical reaction using symbols and formulas

 

2 H2 + O2 2 H2O

Draw molecules on board

Chemical Reaction

Chemical Reaction

Atoms are re-arranged and a new substance with different properties is formed

Reactants Products

Yield, produce

Chemical reaction

Existing bonds are broken, atoms are re-arranged, new bonds are formed to produce new substances

 

Energy is either absorbed or released

Exothermic Reaction

Exothermic chemical reaction (HOT)

Exo “out of” thermic “heat”

 

Heat energy is released

Endothermic Reaction

Endothermic chemical reaction (COLD)

Endo “into” thermic “heat”

 

Heat energy is absorbed

(Need to add heat energy to keep reaction going)

Catalyst

Catalyst

Speeds up a chemical reaction without being permanently being changed itself

Law of Conservation of mass

Law of Conservation of Mass (Matter)

Matter is neither created or destroyed in a chemical reaction. Atoms are re-arranged, however, the same atoms and number of atoms remain on both sides of the reaction.

Balancing equations

Balance chemical equations

Write equations on board

Prepare for unit quiz