UNIT 2: Basic Chemistry

BIG IDEA: Examining substances at the molecular

level helps us understand basic processes of life

Basic Chemistry

• Living and non living things are all made of the same basic building blocks of matter

• Basic life processes all follow the laws of chemistry – Structure of Atoms– Chemical Reactions– Compounds and Mixtures– Water-Acids and Bases

Structure of Atoms

Start big and end small

OrganismsOrgan Systems Organs Tissues Cells Compounds Elements Atoms

Smallest amount of an element that still has the properties of that element.

Atoms have structure and are made up of smaller particles that give them their characteristics and control their interactions with other atoms

ATOM:

Structure of an Atom

P

P

N

N

e

e

Nucleus: Center of atom, where protons and neutrons are located

Structure of an Atom

P

P

N

N

e

e

Orbit: Area outside nucleus where electrons are in constant motion

Orbits spin and rotate in

three dimensions.

P

P

N

N

e

e

Structure of an Atom

Each Orbit is a

specified distance from the nucleus.

P

P

N

N

e

e

Structure of an Atom

Structure of an Atom

PP

N

N

e

e

Nucleus

Orbit

e

ee

e

e

e

e

e

e

Structure of an Atom

An element

has its own number of e, P and N

P

P

N

N

e

e

Structure of an Atom

-

--

++

The different combination of

P, N and e make each

element unique

P

P

N

N

e

e

Structure of an Atom

-

--

++

Main Elements in Human Body

• Oxygen• Carbon• Hydrogen• Nitrogen

Main Elements in Earth’s crust

• Oxygen • Silicon • Aluminum • Iron

- Protons, P+, Charge of +1

- Neutrons, N, zero charge

- Electrons, e-, charge of -1

Atomic particles:

Structure of an Atom

Normally, all the “+” of the protons and the “-” from the electrons balance out and the overall charge of an

atom is zero.

Structure of an Atom

What if an atom loses

an electron? P

P

N

N

e

Structure of an Atom

P

P

N

N

e

e--

++

-

- Atom becomes positive

P

P

N

N

e

e

Structure of an Atom

-

--

++

What if an atom gains an electron?

- Atom becomes negative

e-

Any charged atom is called an ion

Structure of an Atom

- Positive ions are called cations

- Negative ions are called anions

Structure of an Atom-The Periodic Chart

Atomic number is the number of protonsAtomic Mass is the “approximate” number of protons + neutrons

Assume Electrons = Protons (except Ions)

Atomic Mass = Protons + Neutrons

Why don’t the electrons figure in?

Drawing Atoms:

•Each orbit can hold a maximum number of electrons.

- Orbit 1: holds a max of 2 - Orbit 2: holds a max of 8 - Orbit 3: holds a max of 8•You must fill the inner orbits before adding electrons to the outer orbits.

•Electrons in the outermost orbit are called valence electrons

Examples

12

Mg

24

P

P

P

P

P

PPP

P

PP

P NN

N

N N

N

N

N

N

N

N

N

e

e

ee

e

e

e

e

e

e

e

e

Examples

8

O

16

Examples

10

Ne

20

Examples

• Look at the column on periodic table to figure out Valence electrons

• C __________ N____________

Examples

• Look at the column on periodic table to figure out Valence electrons

• O __________ H ____________

Chemical Reactions- Bonds

• Compounds–Atoms are chemically bound together –Definite proportions required–Properties of a compound are different

from the properties of the elements that make up that compound

–Made up of many particles of the same type held together by a bond using the valence electrons

Types of bonds that form Compounds

• Covalent- each atom shares electrons with the other

• Molecules are formed by this type of bond

Types of bonds that form Compounds

•Ionic Bond- One atom gives an electron to the other

IONIC:

• Creates opposite charge that holds atoms together

• Form crystals

Chemical Formulas

• Al2O3

• 2Al2O3

Subscript shows how many atoms of the elementit is written after

This number (co-efficient) shows how many of the entire molecule there are

Chemical Reactions

• Change in the arrangement of atoms that creates a different substanceNumber of atoms before and after the reaction are equal.

A + B C synthesis reaction

A B + C decomposition

A + B C + D Displacement

Chemical Reactions

• Reactants: The “stuff” you start with

• Products: The “stuff” you end up with

A + B C

Reactants Products

Chemical Reactions

C6H12 O6 + C6H12 O6 C12H22O11 + 6H2O

C6H12 O6 + 6O2 6CO2 + 6H2O

H20 H+ + OH-

Mixtures

• Mixtures have “ingredients” that do not bind chemically with each other–Each ingredient keeps its own properties

–Definite proportions not required

–Types: solution, suspension, colloid

Mixtures

–Solution: homogeneous; even throughout; solute (substance) completely dissolves in solvent (liquid) examples: air,

–Suspension: Heterogeneous; looks even if shaken; but particles settle to bottom examples-water column in oceans and lakes

Mixtures

–Colloid: heterogeneous BUT does not settle; sort of in between the other two. Examples-milk and fog

Mixtures vs. Compounds

Look at your notes:

What are three big differences between Mixtures and Compounds?

Properties of Water

Water is held together with special covalent bond called polar covalent bond

- Means water has poles, or ends.

- O is the negative end - H’s are the positive end

Water is the Universal Solvent

• Important solvent in many solutions

• Anything with a charge will attract water molecules and dissolve

• Ionic and polar molecules have charge

• Nonpolar molecules (like fat) do not have charge and will not dissolve

Properties of Water

Properties of Water

Cohesion: Water molecules stick together because of charges

Cohesion

Creates Surface tension - allows stickbugs to walk on

water!

Adhesion

Water molecules stick to other charged substances like glass

Glass stirring

rod

Concept of pH

• pH = power of Hydrogen• A way of measuring how

many Hydrogen ions, H+, there are in a solution

• Determines whether a solution is an acid or a base

Acids and Bases

• Acids: a chemical that when dissolved in water releases a hydrogen ion (H+)

HX (in water) H+ + X-

Properties of Acids

• Taste sour – think of lemon

• Turn litmus paper from blue to red

• Corrodes Metal• Examples: Sulfuric Acid, Lemon Juice, Battery Acid

Acids and Bases

• Base: a chemical that when dissolved in water releases a hydroxide ion (OH-)

XOH (in water) OH- + X+

Properties of Bases

• Taste bitter – cough meds.

• Turn litmus paper back to blue after acid turns it red

• Can cause serious burns• Examples: Bleach, KOH, NaOH

Acids and Bases - Examples

• NaOH + H2O Na+ + OH- + H2O

• HCl + H2O H+ + Cl- + H2O

Acids and Bases will “cancel” each other out

• When an Acid and a Base are mixed together they will “Neutralize” each other and create Water and a Salt

• This is a Neutralization Reaction

Neutralization Reaction

• HCl + NaOH NaCl + H2O

A Salt Water

• HNO3 + KOH KNO3 +H2O

A salt Water

Neutral

(water)

Acid Base

14131211109876543210

High H+

Low OH- H+ = OH-

High OH-

Low H+

pH Scale – a measure of the concentration of Hydrogen Ions

Concept of pH

• Where is the “safe” pH?– pH must stay between 6.5 -

7.5 in the human body– Another factor that must

maintain homeostasis

Concept of pH

• Are there exceptions?– Stomach is acidic– Intestines are basic– Buffers are necessary

• weak acids or bases that react with strong acids or bases to prevent sudden changes in pH

What is the pH of Rain water??

Usually between 5.6- 5.8 - Water reacts with CO2 in

air to form Carbonic Acid (H2CO3)

What is the pH of Rain water??

Acid Rain: - Rain water reacts with

pollutants such as Sulphur dioxide and Nitrogen oxides in air

- Forms Sulphuric Acid, Nitric Acid, Ammonium Sulphate

- Decreases pH even further