Physical Science: The Structure of Matter

Review Part Two

Properties of MatterMatter has physical and chemical properties.

Physical Properties

Phase (solid, liquid, gas)Boiling point

Freezing pointTextureColor

Chemical Properties

Reactivity

Iron is a dark, silver metal that has a high melting

point. It is a solid at room temperature.

Iron reacts with oxygen to make Iron Oxide (rust).

Properties of MatterMatter can change physically and chemically.

Physical Change

Is it boiling, melting, freezing, or is it being

misshapen?

Chemical Change

Has it reacted with other matter to become something new?

When grass is cut, it changes shape, but it is still

grass.

When gasoline burns, it makes heat, CO2, and water.

Mass, Volume, and Density

Mass is the measure of how much material an object is made of.Mass is measured in grams or kilograms.

Volume is how much space an object takes up. Volume is measured in cm3 or mL.

Density is the relationship between mass and

volume. It is measured by dividing

mass by volume.

D=m/v

The unit of measurement is g/cm3 or g/mL.

These cubes have the same volume, but different masses.The more massive cubes are more dense.

Phases of Matter

Solid Liquid Gas

In a solid, the particles are very attracted to

each other. The object holds its own shape, and

the particles simply vibrate in place.

The particles of a liquid have more energy than the

particles of a solid. Liquids take the shape of their

container, and the molecules slide around each other.

The particles of a gas have more energy than in

a liquid. The particles have very little attraction for each other. Gases will

take the shape of their container, and the

molecules fly in every direction.

add energy add energy

Phase Change DiagramThe phase of a pure substance is affected by pressure and temperature.

There are specific names for changing phases.

GREATEST VOLUME

LEAST VOLUME

The Behaviors of Gases

Volume Temperature

When gases expand (increase volume), they absorb energy

(increase temperature).

When gases are compressed, the release energy (decrease

temperature).

Cold air is more dense than warm air.

VolumePressure

VolumePressure

When the pressure of a gas increase, the volume decreases.

If the pressure decreases, then the volume increases.

Phase Change of Water

Atomic Structure

All matter is made of atoms.

Atoms have 2 regions:nucleus

electron cloud

The nucleus is made of protons and neutrons.

The electron cloud only contains electrons.

Protons: positive, 1 amuNeutrons: neutral, 1 amu

Electrons: negative, 0 amu

Atomic Structure

The different kinds of atoms are called elements.

The number of protons determines the identity of the

element (atomic number).

The number of protons and neutrons determines the mass

of the element.

The balance of protons and electrons determines the

charge of the element.Atomic Number: 6Atomic Mass: 12

Charge: 0

The Periodic TableThe Periodic Table is a chart of all of the elements that exist.

There are 18 groups and 7 periods (rows). Element in the same group have similar properties.

The Periodic TableElements on the Periodic Table are either

Metals, Nonmetals, or Metalloids.

The Periodic TableElements on the Periodic Table are either

solids, liquids, or gases.

Reading the Periodic Table

The Electron CloudElectrons are located in a cloud

around the nucleus.

However, the cloud is actually organized. It has energy levels

(rings) and orbits.

Each energy level can only hold so many electrons. When an energy level is full, a new energy level is

needed.

The outer most energy level is called the valence energy level.

ENERGY LEVEL# OF

ELECTRONS IT CAN HOLD

1 2

2 8

3 18

4 32

Valence Electrons

Valence electrons are the electrons that are located on the outer most energy level.

When elements react or bond, it is the valence electrons that interact. This is because when atoms touch, their valence energy levels are in contact.

Although an energy level may be able to hold more than 8 electrons, 8 is considered to be “full.” The only exception is for elements that only have the first energy level, which is full at 2 electrons (Hydrogen for example).

Reading the Periodic TableThe group that an element is in tells the number

of valence electrons that it has.

GROUP VALENCE ELECTRONS

1 1

2 2

13 3

14 4

15 5

16 6

17 7

18 8

1

2 13 14 15 16 17

18

Isotopes

Nitrogen-14Protons: 7

Neutrons: 7

Nitrogen-15Protons: 7

Neutrons: 8

Nitrogen-16Protons: 7

Neutrons: 9

Isotopes are atoms that are the same element, but have different masses (# of neutrons).

IonsIons are elements that have an unbalance of protons and electrons.

If there are more protons, the ion is positive (cation).If there are more electrons, then the ion will be negative (anion).

Count the numbers of protons and electrons to find out what the charge is…

N-3

e

e

e

e e

e

e

e

ee

ee PP

P

N N

N

Li+1

Reading the Periodic TableThe group that an element is in tells what charge it will have.

Metals always form a positive charge(+), and nonmetals form negative charges (-).

GROUP CHARGE

1 +1

2 +2

13 +3

14 +4

15 -3

16 -2

17 -1

18 0

1

2 13 14 15 16 17

18

Nuclear Radiation

Alpha Particle

Beta Particle

Gamma Energy

a b gP

P N

N4He2 e-

The nucleus of a helium atom

Atomic number decreases by 2 amu

Atomic mass decreases by 4 amu

Least harmful

An electron

Mass remains the same, but the

atomic number increases by 1

amu

High energy electromagnetic waves

Most harmful

Nuclear Radiation: Types

P

P N

NUranium-238 Thorium-

234

e-Carbon-14 Nitrogen-14

g

g

a

b

Nuclear Radiation: Fission

238

99 138

ENERGY!!!

In fission, an atom splits into two smaller nuclei. The masses don’t quite add up, because some of the mass was converted into

energy (E=mc2).

Nuclear Radiation: FusionIn fusion, smaller nuclei combine to produce a larger nucleus.

Energy is released when this happens. This is how stars (like our sun) produce energy.

Hydrogen 2

Helium-4

Hydrogen 2

ENERGY!!!

Nuclear Radiation: Half LifeDuring radioactive decay, the amount of radioactive material is cut in half over a certain amount of time. This amount of time never changes, and it is called the half-life.

Scientists can look at a sample of rock, compare the amount of radioactive material to stable material, and determine how old the rock is. They use this information to determine the ages of dinosaurs, meteors, and the Earth.

Nuclear Radiation: Half LifeThe process of radioactive decay usually takes several steps.

Not every isotope will have the same half-life, but the half-life for a certain kind of isotope is always the same.

Some half-lives take years, while others may only take seconds.

Nuclear Radiation: Uses and Dangers

Ionic Compounds

+ -METALSNON

METALS

e

Metals will give electrons to nonmetals so that they both end up with a full valence energy level. This results in the metal becoming positive, and the nonmetal becoming negative.

Therefore, they stick to each other (bond) like magnets.

Ionic Compounds

Dissolving Ionic CompoundsIonic compounds break apart when they are dissolved in water.

This is called dissociation.

Na Cl

Cl-

Cl-

Cl-

Cl-Cl-

Na+

Na+

Na+

Na+

Na+

Water

Sodium Chloride

Because the positive and negative ions are exposed, this solution will conduct electricity.

Ionic CompoundsUse the “criss-cross method” to determine the formula for an ionic compound. When ions bond, the result is a

balance of charges of the ions.

Na+1 + Cl-1 = NaCl

Na+1 + O-2 = Na2O

Mg+2 + Cl-1 = MgCl2

Ca+2 + P-3 = Ca3P2

Naming Ionic CompoundsName the first element, name the second element,

and finish the second element with –ide.

NaCl: sodium chloride

Na2O: sodium oxide

MgCl2: magnesium chloride

Ca3P2: calcium phosphide

Molecular or Covalent CompoundsNonmetals will share electrons so that they all have full valence energy levels. Covalent bonds are stronger than ionic bonds, and the bonded elements are

referred to as molecules.

In this example, both Hydrogen atoms are sharing their one valence electron with Oxygen. This allows

Hydrogen to have 2 total, and Oxygen 8 total. They each have a full valence energy

level.

Naming Molecular & Covalent CompoundsTo name molecular/covalent compounds, use the prefix system.

Don’t ever use mono for the first element. Also, the last element ends in –ide.

Number of Atoms Prefix

1 Mono

2 Di

3 Tri

4 Tetra

5 Penta

6 Hexa

7 Hepta

8 Octa

9 Nona

10 Deca

CO2: carbon dioxide

P2O3: diphosphorus trioxide

Dissolving Molecular/Covalent Compounds

Molecular/Covalent compounds do not dissociate in water. This is because theirs bonds are too strong.

Water

carbohydrate

Conductivity of Ionic & Molecular CompoundsBecause ions dissociate in water, a solution of ions will conduct electricity.

A solution of molecular compounds will not conduct electricity.

Chemical ReactionsUnder the right conditions, elements and compounds will react with each other in order to reach a greater state of equilibrium. The valence electrons determine the reactivity of a substance. Combustion is the reaction between a hydrocarbon and oxygen.

Indicators of Chemical Reactions

How do you know if a chemical reaction is occurring?

1. A precipitation occurs.1. Bubbles2. Solid or liquid precipitation sinks.

2. A change in color.3. Energy is absorbed or released as heat or

light.4. The pH changes (more or less acidic)

Understanding Chemical ReactionsThe ingredients of a chemical reaction are on the left

side of the arrow. They are called reactants.

The products are on the right side of the reaction, and are simply referred to as “products.”

2H2 + O2 2H2OREACTANTS PRODUCTS

Types of Chemical ReactionsKINDS OF REACTIONS EXAMPLES

SYNTHESIS A + B AB

DECOMPOSITION AB A + B

SINGLE REPLACEMENT A + BC B + AC

DOUBLE REPLACEMENT AB + CD AD + CB

COMBUSTION CHO + O2 CO2 + H2O

Balancing Chemical Reactions

2H2 + O2 2H2O

Chemical reactions must be balanced. This means that the mass of the reactants are equal to the mass of the products. Also, there are the same number of each element in

the reactants as there is in the products. The coefficients in front of the compounds/elements determine how many that there are in the reaction.

H H

H H

O O

H HO

H HO

4 grams of Hydrogen react with 32 grams of oxygen to make 36 grams of water

The Periodic Table: ReactivityIn a group, the higher up the element, the more reactive it is.

More Reactive

LessReactive

MIXTURES

HETEROGENEOUS

SUSPENSION EMULSION COLLOID

HOMOGENEOUS

SOLUTION

SOLVENT SOLUTE

Solutions

The water in this pitcher of sweet tea is the solvent. The sugar and tea is the solute.

Water is referred to as the universal solvent, because it can dissolve almost anything.

If you want to make a solute dissolve faster in the solvent, there are three things that you

can do:

1. Heat up the mixture.2. Crush the solute.3. Stir the mixture.

The air that we breathe is also a solution. Most of the air in our atmosphere is nitrogen (75%), and about 23 % is oxygen. That makes nitrogen the solvent and oxygen is the solute.

Solutions: ConcentrationWhich solution has the higher concentration? How do you know?

50 grams of NaCl in 100 mL of water

75 grams of NaCl in 250 mL of water

Solubility Curve of a Solid in a Liquid or a Liquid in a Gas

Solubility

Temperature

UNSATURATED

SATURATED

SUPER-SATURATED

Solubility Curve of a Gas in a Liquid

Solubility

Temperature

UNSATURATED

SATURATED

SUPER-SATURATED

AcidsAcids are aqueous solutions (water) that contain extra Hydrogen Ions (H+). The extra

hydrogen ions turn water molecules into hydronium (H3O+).

Acids are

1. Sour2. Corrosive3. Reactive with metals4. Conduct electricity5. Turns blue litmus paper red6. pH 0-7

BasesBases are aqueous solutions (water) that contain

extra Hydroxide Ions (OH-).

Bases are

1. Bitter2. Slippery3. Conduct electricity4. Turns red litmus paper blue5. pH 7-14

STRONG STRONGWEAK