Ch 3 Notes

Matter-Properties & Changes (p. 54-81)

Section 3.1

Objective: Identify properties of substances (define substance-matter with a uniform & unchanging composition.) Example: pure water. (Alternatively, Salt water is a mixture, not a substance)

Objective: Identify Physical Properties-including intensive & extensive (p. 56)

List Examples of Physical Properties:   physical state, density, color, odor, taste, hardness, melting pt., boiling pt., mass, volume, length, appearance; magnetism, opacity, viscosity, polarity, conductivity, malleability

Intensive vs. Extensive Physical Properties:

Intensive physical properties are independent of the amount of substance present. In other words, it doesn’t matter if you have 1 g or 1 kg of H2O, the boiling point is still 100° C and its density is 1g/mL.  Substances can be identified by their intensive properties.  All the properties listed in table 3-1 on p. 56 are intensive. (Color, state, mp, bp, density)

 

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

 

States of Matter-review definitions of solid, liquid, & gas (& vapor)

 

Before learning about the states of matter you need to know about the Kinetic Molecular Theory.

(all matter is composed of tiny particles, in constant random motion, and the amount of motion is directly proportional to temperature)

Look at the Kinetic molecular theory - Go to this link & Click on Chapter Two: Structure of Matter

 

Here’s a power point lesson that explains solids, liquids & gases

Solid

·         Have definite shape & volume

·         Particles are very tightly packed

·         Incompressible

·         When heated, particles expands only slightly

·         Shape remains consistent, does not conform to shape of container that its placed

 

Liquid

·         Liquids flow (Liquid particles are able to move past each other)

·         Has consistent, definite volume

·         Takes the shape of the container its placed in

·         Particles not rigidly held in place

·         Less closely packed than are the particles of a solid

·         Virtually incompressible (b/c the particles are very close together)

·         Expand when heated

 

Gas

·         a substance that is naturally in the gaseous state at room temp.               

·         Gases flow

·         conform to shape of container

·         fills entire volume of its container. 

·         Particles are far apart

·         Easily compressed

 

Vapor-term reserved for substances that are normally solid or liquid at room temperature, but because of a temperature change, have vaporized.

 

Plasma-The fourth state of matter is plasma. Plasma is an ionized gas, a gas into which sufficient energy is provided to free electrons from atoms or molecules and to allow both species, ions and electrons, to coexist. In effect, a plasma is a cloud of protons, neutrons and electrons where all the electrons have come loose from their respective molecules and atoms, giving the plasma the ability to act as a whole rather than as a bunch of atoms. Plasmas are the most common state of matter in the universe comprising more than 99% of our visible universe and most of that not visible. Plasma occurs naturally and makes up the stuff of our sun, the core of stars and occurs in quasars, x-ray beam emitting pulsars, and supernovas. On earth, plasma is naturally occurring in flames, lightning and the auroras.

On Earth, we only usually encounter solids, liquids, & gases.

 

o   States of matter-dealt with here only as it relates to physical properties; do question #3 on p. 60 –add to study guide p. 14;

 

Solid

Liquid

gas

Shape

Definite

Not definite

Not definite

volume

Definite

Definite

Not definite

compressibility

Not compressible

Virtually incompressible

compressible

 

Identify Chemical Properties p. 57 (See concept map)

Compare & Contrast (here’s a power point that compares & gives examples of Chemical  & Physical Properties and Changes (also see table 3-2 p. 57)

Examples of chemical properties are: flammability, heat of combustion, reactivity with water or other substances, PH;

Chemical Properties (definition) - How a substance reacts to other substances. When one or more substances react they become a third, unique, substance often with new physical and chemical properties.

 

Section 3.2

Changes in Matter- Physical (p.61) vs. Chemical (p. 62) What is your prior knowledge?

“Change” of any kind involves a process, so look for verbs

Physical Changes: result in different appearance, but not a different composition; (rearranges molecules but doesn't affect their internal structures.) Some examples of physical change are:

·         Changes in shape, cutting, bending, grinding, etc.

·         Changes of state (ice melting, boiling water (water molecules are forced away from each other when the liquid changes to vapor, but the molecules are still H2O.)

·         whipping egg whites (air is forced into the fluid, but no new substance is produced)

·         magnetizing a compass needle (there is realignment of groups ("domains") of iron atoms, but no real change within the iron atoms themselves).

·         dissolving sugar in water (sugar molecules are dispersed within the water, but the individual sugar molecules are unchanged.)

 

condense          melt                    sublime          

boil                   freeze                 vaporize

Chemical reactions/changes-

                Rust                       explode                               oxidize                  tarnish

                Corrode               ferment               burn                      rot

Reactants react to form products             Reactants            Products

                                                                                Starting                                                new

                                                                                substances                         substances

What evidence can we observe that a chemical reaction has taken place?

1.       Observe a new product-it looks different & new product has different properties

2.       Formations of gas (bubbles, fizz)

3.       Color change (maybe chemical, but  always)

4.       Energy changes (gets hot or cold, produces light or sound)

5.       Odor is produced

Law of conservation of mass (p.63-64)

Matter cannot be created or destroyed in a chemical reaction. Therefore:

Total mass of reactants = total mass of products

Examples:           2H + O ----> H2O        (notice that every atom is accounted for in the products)

                        Mercury (II) oxide  ----> Mercury + oxygen

                        216 g Mercury (II) oxide    ----> 200 g Mercury + 16 g oxygen
(notice that the mass of the reactant equals the sum of the masses of the products)

·         P. 64 Study example 3-1; do practice problems #6-9; 

·         Also do p. 65 Section 3.2 assessment # 12 a & b

·         Use chem. Com. P.  30-31 “Working with symbols, formulas, & equations”

Section 3.3 Mixtures of matter p. 66-69

2 Broad Categories- Substances & Mixtures

Mixture-combination of 2 or more pure substances in which each pure substance retains its individual chemical properties.

Salt & water form a mixture. They physically mix (salt dissolves) but do not chemically combine.  They can easily be separated by boiling the water away to leave the salt.

2 Categories of Mixtures- Heterogeneous and Homogeneous

Heterogeneous Mixture

Homogeneous Mixture

Individual substances remain distinct; Not uniform appearance;  (hetero- means different)

Constant, uniform composition

(homo-means “same”)

Includes suspensions & colloids (see p. 476)

Also called a “solution”

Example:  Pepperoni Pizza

Example- alloy (steel)

Example:  Sand & water mixture

Example:  salt water mixture

Example:  fruit salad

Example:  soft drinks

 

Separation- done by physical processes; Examples: use a magnet to pick out magnetic substances; use filtration to separate solids from liquids; Use differences in boiling pt. to separate by distillation; Crystallization is when a pure solid crystal forms from a solution; Chromatography ; Read p.68-69.

 Section 3.4 Elements and Compounds

Pure substances can be elements or compounds.

Elements- a pure substance that cannot be broken down into simpler substances by physical or chemical means.  An atom is the smallest particle of an element that has the properties of that element.  Interactive periodic table

Learn names & symbols for the following elements: 1-30, 35, 47, 50, 53, 56, 79, 80, 82, 84, 86, 88.

 

Compounds- a substance formed when 2 or more elements are chemically joined. Water, salt, and sugar are examples of compounds. When the elements are joined, the atoms lose their individual properties and have different properties from the elements they are composed of.  Compounds can be broken down into the simpler substances (by chemical means).

A chemical formula is used a quick way to show the composition of compounds. Letters, numbers, and symbols are used to represent elements and the number of elements in each compound.   Example: Glucose has six carbon atoms, twelve hydrogen atoms and six oxygen atoms, so it’s chemical formula is: C6H12O6.

Law of Definite Proportions p. 75 -regardless of the amount, a compound is always composed of the same elements in the same proportions by mass.  Example: It doesn’t matter whether you have a 20 g sample, or a 500 g sample of table sugar (sucrose), both samples will be composed of 42.2 % Carbon, 6.5% Hydrogen, & 51.3% Oxygen.

Law of Multiple Proportions p. 76-when different cmpds. are formed by a combination of the same elements, different masses of one element combine with the same relative mass of other element.  The ratio of elements is in small whole numbers.

Example:             Water is H2O                     

·         Hydrogen is present in a 2:1 ratio (2/1) with Oxygen

                                Hydrogen Peroxide is H2O2

·         Hydrogen is present in a 2:2 ratio (2/2 ) with Oxygen

                                Water is not the same compound as hydrogen peroxide b/c the ratios are different.

THE END OF CH 3 NOTES!