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UNIT 2: Basic Chemistry BIG IDEA: Examining substances at the molecular level helps us understand basic processes of life
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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
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Structure of Atoms Start big and end small OrganismsOrgan Systems Organs Tissues Cells Compounds Elements Atoms
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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
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Structure of an Atom e N P Nucleus: Center of atom, where protons and neutrons are located P N e
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Structure of an Atom e Orbit: Area outside nucleus where electrons are in constant motion N P P N e
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Orbits spin and rotate in three dimensions.
Structure of an Atom P N e Orbits spin and rotate in three dimensions.
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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.
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Structure of an Atom P N e Nucleus Orbit
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Structure of an Atom
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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
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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
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Main Elements in Human Body
Oxygen Carbon Hydrogen Nitrogen
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Main Elements in Earth’s crust
Oxygen Silicon Aluminum Iron
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Structure of an Atom Atomic particles: - Protons, P+, Charge of +1
- Electrons, e-, charge of -1 - Neutrons, N, zero charge
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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.
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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 -
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Structure of an Atom What if an atom gains an electron? - + + - - e N
P + P N - Atom becomes negative e - - - e
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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
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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)
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Atomic Mass = Protons + Neutrons
Why don’t the electrons figure in?
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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
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Examples e e 12 Mg 24 e P N
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Examples 8 O 16
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Examples 10 Ne 20
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Examples Look at the column on periodic table to figure out Valence electrons C __________ N____________
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Examples Look at the column on periodic table to figure out Valence electrons O __________ H ____________
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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
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Types of bonds that form Compounds
Covalent- each atom shares electrons with the other Molecules are formed by this type of bond
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Types of bonds that form Compounds
Ionic Bond- One atom gives an electron to the other
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IONIC: Creates opposite charge that holds atoms together Form crystals
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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
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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
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Chemical Reactions A + B C Reactants: The “stuff” you start with
Products: The “stuff” you end up with A + B C Reactants Products
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Chemical Reactions C6H12 O6 + 6O2 6CO2 + 6H2O
C6H12 O6 + C6H12 O6 C12H22O11 + 6H2O H20 H+ + OH-
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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
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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
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Mixtures Colloid: heterogeneous BUT does not settle; sort of in between the other two. Examples-milk and fog
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Mixtures vs. Compounds Look at your notes:
What are three big differences between Mixtures and Compounds?
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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
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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
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Properties of Water
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Properties of Water Cohesion: Water molecules stick together because of charges
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Cohesion Creates Surface tension - allows stickbugs to walk on water!
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Adhesion Water molecules stick to other charged substances like glass
Glass stirring rod
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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
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Acids and Bases Acids: a chemical that when dissolved in water releases a hydrogen ion (H+) HX (in water) H+ + X-
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Properties of Acids Taste sour – think of lemon Turn litmus paper from blue to red Corrodes Metal Examples: Sulfuric Acid, Lemon Juice, Battery Acid
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Acids and Bases Base: a chemical that when dissolved in water releases a hydroxide ion (OH-) XOH (in water) OH- + X+
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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
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Acids and Bases - Examples
NaOH + H2O Na+ + OH- + H2O HCl + H2O H+ + Cl- + H2O
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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
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Neutralization Reaction
HCl + NaOH NaCl + H2O A Salt Water HNO3 + KOH KNO3 +H2O A salt Water
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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-
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Concept of pH Where is the “safe” pH? pH must stay between in the human body Another factor that must maintain homeostasis
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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
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What is the pH of Rain water??
Usually between Water reacts with CO2 in air to form Carbonic Acid (H2CO3)
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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
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