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 OrganismsOrgan Systems  Organs  Tissues Cells  Compounds Elements Atoms

ATOM: 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

Structure of an Atom e N P Nucleus: Center of atom, where protons and neutrons are located P N e

Structure of an Atom e Orbit: Area outside nucleus where electrons are in constant motion N P P N e

Orbits spin and rotate in three dimensions. Structure of an Atom P N e Orbits spin and rotate in three dimensions.

Each Orbit is a specified distance from the nucleus. Structure of an Atom P N e Each Orbit is a specified distance from the nucleus.

Structure of an Atom P N e Nucleus Orbit

Structure of an Atom

An element has its own number of e, P and N Structure of an Atom - e An element has its own number of e, P and N N + P + P N - - e

The different combination of P, N and e make each element unique Structure of an Atom - e The different combination of P, N and e make each element unique N + P + P N - - e

Main Elements in Human Body Oxygen Carbon Hydrogen Nitrogen

Main Elements in Earth’s crust Oxygen Silicon Aluminum Iron

Structure of an Atom Atomic particles: - Protons, P+, Charge of +1 - Electrons, e-, charge of -1 - Neutrons, N, zero charge

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.

What if an atom loses an electron? Structure of an Atom - What if an atom loses an electron? e e N N + P P + P P N N - Atom becomes positive - e -

Structure of an Atom What if an atom gains an electron? - + + - - e N P + P N - Atom becomes negative e - - - e

Any charged atom is called an ion Structure of an Atom Any charged atom is called an ion - Positive ions are called cations - Negative ions are called anions

Structure of an Atom-The Periodic Chart Atomic number is the number of protons Atomic 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 e e 12 Mg 24 e P N

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 element it is written after This number (co-efficient) shows how many of the entire molecule there are

A + B  C synthesis reaction A  B + C decomposition Chemical Reactions Change in the arrangement of atoms that creates a different substance Number 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 A + B  C Reactants: The “stuff” you start with Products: The “stuff” you end up with A + B  C Reactants Products

Chemical Reactions C6H12 O6 + 6O2  6CO2 + 6H2O C6H12 O6 + C6H12 O6  C12H22O11 + 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

pH Scale – a measure of the concentration of Hydrogen Ions Acid Neutral (water) Base 1 2 3 4 5 6 7 8 9 10 11 12 13 14 High H+ Low OH- High OH- Low H+ H+ = OH-

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