Chemistry of LifeChemistry of Life

Chapter 2Chapter 2

Why Learn Chemistry in Biology?Why Learn Chemistry in Biology? MatterMatter: anything that has mass and takes up space: anything that has mass and takes up space

EVERYTHING is matter; water, air, EVERYTHING is matter; water, air, living thingsliving things, etc, etc Matter is NOT light, sound, or energyMatter is NOT light, sound, or energy

ALLALL matter is made of atoms ( matter is made of atoms (living thingsliving things too!) too!) An An atomatom is the smallest unit of matter that cannot be is the smallest unit of matter that cannot be

broken down by chemical means.broken down by chemical means. An An elementelement is a substance made of only one kind of is a substance made of only one kind of

atom, and it is therefore a pure substance.atom, and it is therefore a pure substance. All elements are found on the Periodic TableAll elements are found on the Periodic Table EVERYTHING IN THE WORLD can be broken down into the EVERYTHING IN THE WORLD can be broken down into the

elements on the tableelements on the table

Parts of an AtomParts of an Atom

All atoms have 3 partsAll atoms have 3 parts ProtonProton: P+, positive (+) charge, found in the : P+, positive (+) charge, found in the

nucleusnucleus NeutronNeutron: N, neutral (0) charge (no charge), found : N, neutral (0) charge (no charge), found

in the nucleusin the nucleus ElectronElectron: e-, negative (-) charge, found in the : e-, negative (-) charge, found in the

electron cloud around the nucleuselectron cloud around the nucleus Atoms are NEUTRAL. Protons (+) are attracted Atoms are NEUTRAL. Protons (+) are attracted

to the electrons (-). to the electrons (-). Atoms have the same number of protons and electronsAtoms have the same number of protons and electrons

Atoms and ElementsAtoms and Elements Elements are made of only 1 kind of atomElements are made of only 1 kind of atom

Example: oxygen is an element made of only Example: oxygen is an element made of only oxygen atomsoxygen atoms

Each element has a specific number of Each element has a specific number of protons, neutrons, and electronsprotons, neutrons, and electrons Example: oxygen has 8 p+, 8 n, and 8 e-Example: oxygen has 8 p+, 8 n, and 8 e-

Changes in p+, n, and e-Changes in p+, n, and e- *IF YOU CHANGE THE NUMBER OF PROTONS IN AN *IF YOU CHANGE THE NUMBER OF PROTONS IN AN

ELEMENT, YOU GET A NEW ELEMENT!!!!!ELEMENT, YOU GET A NEW ELEMENT!!!!!

IsotopeIsotope: atoms that contain different numbers of : atoms that contain different numbers of neutronsneutrons Carbon has 6 protons, 6 neutrons, and 6 electronsCarbon has 6 protons, 6 neutrons, and 6 electrons Carbon can have isotopes with different numbers of neutrons, C-Carbon can have isotopes with different numbers of neutrons, C-

12, C-13, C-1412, C-13, C-14 *all still have 6 protons!!!!*all still have 6 protons!!!!

IonIon: atoms that have different numbers of : atoms that have different numbers of electronselectrons Have an overall electrical chargeHave an overall electrical charge

Negative if it has extra electronsNegative if it has extra electrons Positive if it is missing electronsPositive if it is missing electrons *still has the same number of protons!*still has the same number of protons!

ATOMIC STRUCTUREATOMIC STRUCTURE

the number of protons in an atom and the number of electrons

For Helium: p=2, e=2

the number of protons and neutrons in an atomp + n = mass numberOr mass – p = neutrons

HeHe22

44 Mass Number

Atomic number

number of protons = number of electrons

Counting p+, n, and e-Counting p+, n, and e-

To find the number of To find the number of protonsprotons:: Look at the atomic numberLook at the atomic number

To find the number of To find the number of electronselectrons:: Same as proton numberSame as proton number

To find the number of To find the number of neutronsneutrons:: Subtract protons from massSubtract protons from mass Mass – p = neutronsMass – p = neutrons

BondingBonding Atoms can combine (bond) together to form Atoms can combine (bond) together to form

compounds and moleculescompounds and molecules

CompoundCompound: a substance made of joined atoms, : a substance made of joined atoms, can be the same element or different onescan be the same element or different ones Example: H2O (water), NaCl (salt) Example: H2O (water), NaCl (salt)

• MoleculeMolecule – a group of atoms held together – a group of atoms held together by covalent bondsby covalent bonds

Covalent BondCovalent Bond

Covalent BondCovalent Bond: atoms bond together and : atoms bond together and SHARESHARE electrons electrons Molecule has no chargeMolecule has no charge Water (H2O) is formed when oxygen makes a Water (H2O) is formed when oxygen makes a

covalent bond and shares electrons with 2 covalent bond and shares electrons with 2 hydrogen atomshydrogen atoms

Ionic BondIonic Bond

Ionic BondIonic Bond: forms when 2 or more atoms : forms when 2 or more atoms gain or lose electrons and combine gain or lose electrons and combine electricallyelectrically Ex: sodium (Na) is positive, chlorine (Cl) is Ex: sodium (Na) is positive, chlorine (Cl) is

negative. They form an ionic bond because the negative. They form an ionic bond because the Na+ is attracted to the Cl-Na+ is attracted to the Cl-

Hydrogen BondHydrogen Bond

Hydrogen BondHydrogen Bond: a weak bond formed : a weak bond formed between the hydrogen atoms in a compoundbetween the hydrogen atoms in a compound Water and DNA have hydrogen bondsWater and DNA have hydrogen bonds

Chemical Reactions (rxns)Chemical Reactions (rxns) Molecules become rearranged into other Molecules become rearranged into other

moleculesmolecules Bonds are broken and new ones formBonds are broken and new ones form May release or absorb energyMay release or absorb energy ReactantsReactants = starting materials (on left of rxn) = starting materials (on left of rxn) ProductsProducts = ending materials (on right of rxn) = ending materials (on right of rxn) Same # of each type of atom must be present Same # of each type of atom must be present

on each sideon each side Example: NaOH + HCl Example: NaOH + HCl NaCl + H2O NaCl + H2O

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Bohr ModelsBohr Models Bohr ModelBohr Model – a drawing of an atom with the correct – a drawing of an atom with the correct

number of protons, neutrons, and electronsnumber of protons, neutrons, and electrons1. Find the atomic number. Write that in the middle with a 1. Find the atomic number. Write that in the middle with a

“p” next to it. Circle it. This is your number of protons“p” next to it. Circle it. This is your number of protons

2. Find the mass number. Subtract the number of protons 2. Find the mass number. Subtract the number of protons from the mass number. This is your number of neutrons. from the mass number. This is your number of neutrons. Write that next to the proton number with an “n” next to Write that next to the proton number with an “n” next to it. Circle it.it. Circle it.

3. Protons and neutrons are found in the nucleus. You’ve just 3. Protons and neutrons are found in the nucleus. You’ve just made that!made that!

Bohr Models (continued)Bohr Models (continued)4. Electrons are found in “shells” in a cloud around the 4. Electrons are found in “shells” in a cloud around the

nucleus (called the “electron cloud”nucleus (called the “electron cloud”Find the atomic number. This is your number of Find the atomic number. This is your number of electronselectrons

5. Shells have specific numbers of electrons that can 5. Shells have specific numbers of electrons that can fitfit11stst shell = 2 shell = 222ndnd shell = 8 shell = 833rdrd shell = 8 shell = 844thth or more shells = 18 or more shells = 18

Bohr ModelBohr Model

With Bohr Model diagrams, elements and

compounds are represented by dots to show

electrons, and circles to show the shells. For

example;

Nitrogen 7p+7n⁰ XX X

X

XX

X

N

Why is water so important?Why is water so important?

70% of your body is made of water70% of your body is made of water Almost 70% of the earth is covered with waterAlmost 70% of the earth is covered with water Cells are filled with water, surrounded by Cells are filled with water, surrounded by

water, and need you to drink water to stay water, and need you to drink water to stay healthyhealthy

Water is made of 2 hydrogen atoms covalently Water is made of 2 hydrogen atoms covalently bonded to 1 oxygen atom (H2O)bonded to 1 oxygen atom (H2O)

Properties of waterProperties of water

Water stores heatWater stores heat A pot of boiling water takes a long A pot of boiling water takes a long

time to cool down to room time to cool down to room temperaturetemperature

A warm ocean or lake will take a A warm ocean or lake will take a long time (many months to freeze)long time (many months to freeze)

Water is released from your body Water is released from your body as sweat to help you cool down as sweat to help you cool down when you are hot (*homeostasis*)when you are hot (*homeostasis*)

Properties of waterProperties of water

Water bonds to itself and other substancesWater bonds to itself and other substances

Cohesion: water can bond to itselfCohesion: water can bond to itself Reason you can “overfill” a glass of water and it not spillReason you can “overfill” a glass of water and it not spill

Adhesion: water can bond to other thingsAdhesion: water can bond to other things Reason that dew and condensation on glasses can leave Reason that dew and condensation on glasses can leave

drips still attached to the surface and not fall offdrips still attached to the surface and not fall off

COHESIONCOHESION ADHESIONADHESION

WATER WATER MOLECULE MOLECULE

((POLARPOLAR MOLECULE) MOLECULE)• PolarityPolarity: substances that are : substances that are neutral can have ends, or “poles” neutral can have ends, or “poles” that are slightly positive and that are slightly positive and slightly negativeslightly negative•Water is Polar – the oxygen is Water is Polar – the oxygen is slightly negative and the slightly negative and the hydrogens are slightly positivehydrogens are slightly positive•*reason for “hydrogen bonding”**reason for “hydrogen bonding”*

Properties of WATERProperties of WATERWater is the SOLVENT of Life!

Solute – substance that is dissolved

Solvent – substance that does the dissolving

Solution – a mixture in which 1 or more substances are evenly distributed in another substance

AcidsAcids Definition: a compound that donates H+ Definition: a compound that donates H+

ions to a solutionions to a solution EXAMPLE: HClEXAMPLE: HCl

In a solution, HCl breaks apart into H+ and In a solution, HCl breaks apart into H+ and Cl- ionsCl- ions

BasesBases Definition: a compound that removes H+ Definition: a compound that removes H+

ions from a solutionions from a solution EXAMPLE: NaOHEXAMPLE: NaOH

In a solution, NaOH breaks apart into Na+ In a solution, NaOH breaks apart into Na+ and OH- ionsand OH- ions

The pH ScaleThe pH Scale

Definition: describes how acidic or basic a Definition: describes how acidic or basic a solution issolution is

Ranges from zero (most acidic) to 14 (most Ranges from zero (most acidic) to 14 (most basic)basic)

The numbers 0-14 represent a 10-fold changeThe numbers 0-14 represent a 10-fold change Example: lemon juice pH = 2Example: lemon juice pH = 2 Grapefruit juice pH = 3Grapefruit juice pH = 3 Lemon juice has 10 times more H+ ions than Lemon juice has 10 times more H+ ions than

grapefruit juicegrapefruit juice

pHpH Acid pH = 0-6Acid pH = 0-6 Acids have more H+ ionsAcids have more H+ ions

Strong acid (SA) = 0-3Strong acid (SA) = 0-3 Weak acid (WA) = 4-6Weak acid (WA) = 4-6

Neutral = 7Neutral = 7 Neutral solutions have equal H+ and OH-Neutral solutions have equal H+ and OH- Base pH = 8-14Base pH = 8-14 Bases have more OH- ionsBases have more OH- ions

Strong base (SB) = 11-14Strong base (SB) = 11-14 Weak base (WB) = 8-10Weak base (WB) = 8-10

BuffersBuffers

Definition: substances that cause a solution to Definition: substances that cause a solution to resist a change in pHresist a change in pH

Works by accepting H+ ions when their levels Works by accepting H+ ions when their levels rise (by adding acid) or donating H+ ions rise (by adding acid) or donating H+ ions when the levels drop (by adding base)when the levels drop (by adding base)

Buffers work to maintain a neutral pH (7)Buffers work to maintain a neutral pH (7) Your blood is a buffer – you can eat lots of foods Your blood is a buffer – you can eat lots of foods

with acids or bases and still keep neutral!with acids or bases and still keep neutral!