Name the levels of life from the smallest to the largest!!!

Name the levels of life from the smallest to the largest!!!

Learning checkList levels of life.

Name 3 subatomic particles, charges, how to calculate and location

What is in the element box?

Important elements in organisms

Why do we use Bohr models and Lewis Dot structure?

Can you draw an atom using Bohr’s model?

Define an isotope and how are they used?

Describe how the periodic table is organized.

Learning Check• Periods vs. Groups• Counting atoms in compounds• How compounds are formed• Parts of an equation• Explain why atoms bond• Ions – positive and negative• Describe functions of ions in organisms• Draw compounds bonding – ionic and

covalent

Levels of the Organization of Life

• Subatomic particle organism• Atom populations• Molecule(compound) community• Organelle ecosystem(biome)• Cell biosphere• Tissue• Organ• Organ system

What is this a picture of ? Name 3 facts about this object!

ELEMENTS, ATOMS, AND MOLECULES

Copyright © 2009 Pearson Education, Inc.

How are atoms studied?• Atoms are the building blocks of matter

• Atoms are too small in size to study easily

• Size of Earth : soda can = soda can : atom

Democritus• Not until around 460 B.C., did a Greek

philosopher, Democritus, develop the idea of atoms. He asked this question: If you break a piece of matter in half, and then break it in half again, how many breaks will you have to make before you can break it no further? Democritus thought that it ended at some point, a smallest possible bit of matter. He called these basic matter particles, atoms.

Democritus

• He said in the world this was “atoms and void”. No space between the atoms.

ATOMS

Atoms: smallest unit of matter that still retains the properties of an element..

2.4 Atoms consist of protons, neutrons, and electrons

• An atom is the smallest unit of matter that still retains the properties of a element– Atoms are made of over a hundred subatomic particles,

but only three are important for biological compounds– Proton—has a single positive electrical charge (nucleus)– Electron—has a single negative electrical charge (shells)– Neutron—is electrically neutral (nucleus)


Electroncloud

Protons

2e–Nucleus

Electrons

Massnumber = 4Neutrons

2

2

2

Protons

Protons are located in the nucleus of the atom. They are positively charged.

Neutrons

Neutrons are located in the nucleus.They have NO charge!

ElectronsElectrons are located in the shells around the atom.They are negatively charged.

Electron shells

a) Atomic number = number of Electrons

b) Electrons vary in the amount of energy they possess, and they occur at certain energy levels or electron shells.

c) Electron shells determine how an atom behaves when it encounters other atoms

Parts of an Atom

Protons and neutrons make up the nucleus and has the most mass. Electrons do not weigh as much. SO the atomic mass is only the Protons + the Neutrons

How Do You Think These Pictures are Related?

What do you think is in this picture?

Atoms make up substances called elements which are

the building blocks of matter.There are 110 elements

2.1 Living organisms are composed of about 25 chemical elements

• Living organisms are composed of matter, which is anything that occupies space and has mass (weight)– Matter is composed of chemical elements

– Element—a substance that cannot be broken down to other substances

– There are 92 elements in nature—only a few exist in a pure state

– Life requires 25 essential elements; some are called trace elements


1. ELEMENTS ARE PURE SUBSTANCES MADE OF ONLY 1 KIND OF ATOM AND ARE THE BUILDING BLOCKS OF MATTER.

2. ELEMENTS CANNOT BE BROKEN DOWN INTO A SIMPLER SUBSTANCE

3. ELEMENTS HAVE THEIR OWN UNIQUE SET OF PROPERTIES THAT NO OTHER ELEMENT HAS.

• ELEMENTS ARE MADE OF ONLY 1 KIND OF ATOM

• SOME COMMON ELEMENTS

– HYDROGEN (H), HELIUM (He), OXYGEN (0),

– Notice that the first letter is capital and the next letter is lower case.

Why Are Elements Different?

• Elements differ in their number of protons, neutrons, and electrons. This is why their atomic numbers and masses are different.

• Helium has two protons, two neutrons, and two electrons

• Carbon has six protons, six neutrons, and six electrons


Why Do Some Elements Have Different Symbols?

They are older elements that were name in a different language like Latin.

Copper – cuprumIron – FerrousGold - aurumSilver - argentum

Elements in Organisms• 4 elements that make up 96% of human

body: Carbon(C), Hydrogen(H), Oxygen(O), Nitrogen(N)

There are 11 elements of which most living things are composed.

The most abundant element in the human body is oxygen.

The second most abundant element in the human body is carbon, and in third place is hydrogen. Together, these three elements make up 92% of a human being.

2.2 CONNECTION: Trace elements are common additives to food and water

• Some trace elements are required to prevent disease– Without iron, your body cannot transport oxygen– An iodine deficiency prevents production of thyroid

hormones, resulting in goiter


2.2 CONNECTION: Trace elements are common additives to food and water

• Several chemicals are added to food for a variety of reasons– Help preserve it– Make it more nutritious– Make it look better

• Check out the “Nutrition Facts” label on foods and drinks you purchase


Where Do you Find a Information on All Elements?

Element Info in Each Box

Atomic weightAtomic NumberSymbol Name

Information from the periodic table

Atomic Number- Number of Protons in an atom

Silver = 47 protons

Atomic Weight - total number of particles in an atom's nucleus

Atomic Weight is not very helpful – you need to find the atomic mass

To find the Atomic Mass:

Round the atomic weight

Krypton's mass number is 84 since its atomic weight, 83.80, rounds up to 84.

Mass Number = (Number of Protons) + (Number of Neutrons)

84 = 36 + 48

2.4 Atoms consist of protons, neutrons, and electrons

• Neutrons and protons are packed in the atom’s nucleus– The negative charge of electrons and the positive

charge of protons keep electrons near the nucleus– The number of protons is the atom’s atomic number

– Carbon with 6 protons has an atomic number of 6

– The mass number is the sum of the protons and neutrons in the nucleus (carbon-12 is written 12C)


VALENCE ELECTRONS

• Number of electrons in the outermost. Determines how the element will bond.

GROUPS: determined by valence electrons.

Group 1 – one valence electron

Group 2 – 2 valence electrons

Now let’s learn how to draw an element

• Two models we will use:

1.Bohr’s model

2.Lewis Dot Structure

How do you calculate Valance Electrons?

You determine the number of electrons.Then place the electrons in electron shells.Bohr’s Model: This is a model used to place

electrons in their shells.

Bohr Diagrams1) Find your element on the periodic table.

2) Determine the number of electrons – it is the same as the atomic number.

3) This is how many electrons you will draw.

4) The number of shells are determined by the period.

Bohr Diagrams

CC

1) Draw a nucleus with the element symbol inside. Place Protons and neutrons in the nucleus.

2) The electrons will go in the orbits around the nucleus. Fill order of

shells, 2,8,8,18.

3) Place an X over the atom. This splits the atom into quarters. Since electrons are negative and repel each other place electrons into different quarters. Clockwise!

4) Place all electrons until gone!

Magnesium

Lithium

Hydrogen

Thirdshell

Firstshell

Secondshell

Sodium

Beryllium

Aluminum

Boron

Silicon

Carbon

Phosphorus

Nitrogen

Sulfur

Oxygen

Chlorine

Fluorine

Argon

Neon

Helium

2.6 Electron arrangement determines the chemical properties of an atom

• An atom may have one, two, or three electron shells– The number of electrons in the outermost shell

determines the chemical properties of the atom– The first shell is full with two electrons, whereas the

second and third will hold up to eight electrons


Bohr Diagrams

1) Add the electrons.

2) Phosphorous has 15 electrons.

3) The first shell can only hold 2 electrons.

Lewis Dot Structure

Copy the instructions from the sheet I gave you!!!!!!!

This is an easier way to drawElectrons in shells!!!!This is how you will draw atoms bonding!!!!

Electron Dot Structures

Symbols of atoms with dots to represent the valence-shell electrons

1 2 13 14 15 16 17 18

H He:

Li Be B C N O : F :Ne :

Na Mg Al Si P S :Cl :Ar :

Isotopes

Atoms with the same number of protons, but

different numbers of neutrons.

Atoms of the same element (same atomic

number) with different mass numbers

Isotopes of chlorine

35Cl 37Cl17 17

chlorine - 35 chlorine - 37

2.5 CONNECTION: Radioactive isotopes can help or harm us

• Living cells cannot distinguish between isotopes of the same element– Therefore, when radioactive compounds are used in

metabolic processes, they act as tracers– Radioactivity can be detected by instruments

• With instruments, the fate of radioactive tracers can be monitored in living organisms


Isotopesof an element have

different mass numbers

because

they have

different numbers of neutrons,

but they have

the same atomic number.


• Radioactive tracers are frequently used in medical diagnosis

• Sophisticated imaging instruments are used to detect them– An imaging instrument that uses positron-emission

tomography (PET) detects the location of injected radioactive materials

– PET is useful for diagnosing heart disorders and cancer and in brain research



• In addition to benefits, there are also dangers associated with using radioactive substances– Uncontrolled exposure can cause damage to some

molecules in a living cell, especially DNA– Chemical bonds are broken by the emitted energy,

which causes abnormal bonds to form


Learning Check AT 2

Naturally occurring carbon consists of three isotopes, 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of these carbon atoms.

12C 13C 14C 6 6 6

#P _______ _______ _______

#N _______ _______ _______

#E _______ _______ _______

• http://www.idph.state.ia.us/eh/common/pdf/radiological_health/radioisotopes.pdf

ISOTOPIC NOTATIONisotopes are atoms with the same number of

protons but different number of neutrons

A

Z X

A = mass number (the total number of protons + neutrons)

Z = atomic number (the total number of protons)

X = element symbol

PRACTICE PROBLEMS

15N # protons = ____ # neutrons= ____ #electrons = ___

35P # p = ____ # n= ____ #e- = ___

62Cu2+

# p = ____ # n= ____ #e- = ___

76Se3-

# p = ____ # n= ____ #e- = ___

7 8 7

15 20 15

29 33 27

34 42 37

1. ELEMENTS ARE ORGANIZED IN THE PERIODIC TABLE ACCORDING TO ATOMIC NUMBER

Ways the Periodic Table is Organized

2. ELEMENTS ARE ORGANIZED IN THE PERIODIC TABLE OF ELEMENTS ACCORDING TO THEIR SIMILAR CHARACTERISTICS

• 3 major groups: metals, nonmetals and metalloids

Arrangement of the Periodic table

3. Periods – Rows are called periods. The Elements in these rows have the same number of electron shells.

4. Groups – Columns are called groups. These elements have the same properties because of the number of valence electrons.

Bohr Diagrams• Find out which period

(row) your element is in.

• Elements in the 1st period have one energy level.

• Elements in the 2nd period have two energy levels, and so on.

www.chem4kids.com

http://www.chem4kids.com/

Groups When a column goes from top to bottom, it's called a group.

Groups are often called families because these elements seem to be related.

**Elements in the same group show similarities in their chemical and physical properties.

Valence Electrons

The number of valence electrons determines how an atom will bond.The behavior of an atom is determined by its electrons.

Shell Numb

er

Maximum Number of Electrons in the Shell

1 2 x 1 = 2

2 2 x 4 = 8

3 2 x 9 = 18

4 2 x 16 = 32

5 2 x 25 = 50

2.3 Elements can combine to form compounds

• Compound—a substance consisting of two or more different elements combined in a fixed ratio– There are many compounds that consist of only two

elements– Table salt (sodium chloride or NaCl) is an example– Sodium is a metal, and chloride is a poisonous gas– However, when chemically combined, an edible compound

emerges


• MOLECULES ARE 2 OR MORE ATOMS ATTACHED TOGETHER

– THEY CAN BE THE SAME KIND (ELEMENTS)

– THEY CAN BE DIFFERENT KINDS Just one molecule of a COMPOUND!!

Examples: H2O, NaCl, H2, O2, N2 .

How Compounds Form• FOR A COMPOUND TO FORM, A

CHEMICAL CHANGE MUST TAKE PLACE (A REACTION)

• THE ELEMENTS THAT COMBINE MAKE A NEW SUBSTANCE WITH NEW PHYSICAL PROPERTIES

• COMPOUNDS CANNOT BE BROKEN DOWN PHYSICALLY. REQUIRES A CHEMICAL CHANGE

• MORE COMMON THAN ELEMENTS

Common Compounds for Life

• CO2

• H2O

• C6H12O6

• NaCl

• COMPOUNDS ARE MADE OF 2 OR MORE DIFFERENT KINDS OF ELEMENTS.

• COMPOUNDS ARE IDENTIFIED BY A CHEMICAL FORMULA

+ =

NaClTABLE SALT

Why Do Elements Bond to Form Compounds?

Elements bond to fill their outer shell and become stable!!!

THEY WANT TO BE HAPPY

Sodium ChlorideChlorineSodium

+

Sodium

Chlorine

Sodium Chloride

The elements lose their properties in a compound!

How to Count AtomsChemical Formula

Definition – Short way to write a compound using symbols.Subscript – Small number that is written below the element.

Coefficient – The large number in front of the symbols.

Subscripts• A subscript refers to the number found on the lower

right side of an element or attached to a compound.

• These numbers tell you how many atoms of which elements the equation is made up of.

• In this equation it explains that, on the product side, there are 2 hydrogen atoms as well as 2 oxygen atoms.

• A subscript can never be changed to balance an equation.

.

Ba(OH)2 – 1) In this compound there are three different elements (Ba), Oxygen (O) and Hydrogen (H). 2) In this compound the subscript 2 goes with the O and H3) Since Ba is not in the parentheses and it does not have a subscript there is one Ba. 4. Oxygen is in the parentheses and the two elements in the paraentheses so there parentheses are Oxygen (O) and Hydrogen (H) is 2. Same for Hydrogen.

Coefficients• In other words a coefficient is used to display 2 or

more of the entire unit it appears in front of. The coefficient used in this example shows that, in the left reactant, there are 4 hydrogen, and in the product, there are 4 hydrogen and 2 oxygen.

• The coefficient does not effect the oxygen in the reactant because it is not a compound with hydrogen but is separated by the plus sign.

Chemical Changes Through Chemical Reactions

A chemical reaction – Process in which the physical and chemical properties of the original substance change as new substances with different properties are formed

http://www.eepybird.com/dcm1.html



CHEMICAL REACTIONSCHEMICAL REACTIONS

Reactants: Zn + IReactants: Zn + I22 Product: Zn IProduct: Zn I22

!

What is a Chemical Equation?

• A chemical equation is described as a symbolic representation of a chemical reaction.

• The reactants of the reaction are found on the left and the products on the right, separated by an equal sign or directional arrows

What Makes up a Chemical Equation?

• There are several parts that make up a chemical equation, other then the 3 previously listed (reactants,

• products,

• and the yield symbol).

– Chemical reactions occur when bonds between the outermost parts of atoms are formed or broken

– Chemical reactions involve changes in matter, the making of new materials with new properties, and energy changes.

– Symbols represent elements, formulas describe compounds, chemical equations describe a chemical reaction

IntroductionIntroduction

• The charcoal used in a grill is basically carbon. The carbon reacts with oxygen to yield carbon dioxide. The chemical equation for this reaction, C + O2 CO2, contains the same information as the English sentence but has quantitative meaning as well.

• Show video of gummi bear and zinc and H gas!!!!

Equation for gummi bear

2KClO3 -- 2KCl + O2 melting

C6H12O6 +6O2 ----- 6CO2 + 6H2O

The energy released is coming from the bonds in the sugar!! This is where we get our energy!!!

Why do elements bond?• Elements bond to fill their outer shells.

This make the element stable. TO BE HAPPY!

• Elements will either gain, lose or share electrons to fill their outer shell.

http://www.google.com/imgres?imgurl=http://www.cholesterol-and-health.com/images/Hydroxyl_Real_3.jpg&imgrefurl=http://cmhsbonding.wikispaces.com/Iodine1&usg=__M9Qj9x9iZfp0is8ej2gkYXA9N6U=&h=180&w=224&sz=11&hl=en&start=1&um=1&itbs=1&tbnid=7Xvsk_f14QgWFM:&tbnh=87&tbnw=108&prev=/images?q=elements+bonding&um=1&hl=en&rlz=1T4RNWN_en___US208&ndsp=20&tbs=isch:1

2.7 Ionic bonds are attractions between ions of opposite charge

• An ion is an atom or molecule with an electrical charge resulting from gain or loss of electrons– When an electron is lost, a positive charge results; when

one is gained, a negative charge results

• Two ions with opposite charges attract each other– When the attraction holds the ions together, it is called

an ionic bond


Animation: Ionic Bonds

An ion is an atom, or group of atoms, that has a net positive or negative charge.

cation – ion with a positive chargeIf a neutral atom loses one or more electronsit becomes a cation.

anion – ion with a negative chargeIf a neutral atom gains one or more electronsit becomes an anion.

Na 11 protons11 electrons Na+ 11 protons

10 electrons

Cl 17 protons17 electrons Cl-

17 protons18 electrons

2.5

Formation of Ions from Metals

Ionic compounds result when metals react with nonmetals

Metals lose electrons to match the number of valence

electrons of their nearest noble gas

Positive ions form when the number of electrons are

less than the number of protons

Group 1 metals ion 1+

Group 2 metals ion 2+

• Group 13 metals ion 3+

Formation of Sodium Ion

Sodium atom Sodium ion

Na – e Na +

2-8-1 2-8 ( = Ne)

11 p+ 11 p+

11 e- 10 e-

0 1+

2.5

Ions Function• There are nine types of most

essential ions of our body which plays a role in supporting and sustaining health and life.

• Out of nine, five are positively charged ions and four are negatively charged ions.

Ion (Electrolytes) Function• The positively charged ions are

called cations ; these are Na+ , K+ , Ca++ , Mg++, and H+ .

• The negatively charged ions are called anions ; these are Cl- , HCO3- , PO43- , and OH- .

Electrolytes Functions

• The Sodium (Na+), Chloride (Cl-), Potassium (K+) and Bicarbonate (HCO3-) are called principle electrolytes and are present in the blood and various body fluids.

• Potassium (K+) is essential for heart function.

• Our kidneys play a vital role in maintaining the electrolyte balance. They filter out excess!! Over work them!!!

• The osmosis regulates the movement of water in cells. Theconcentration of electrolytes or ions to a moves water from higher concentration of electrolytes or ions to areas or lower concentration.

• Using ion channels, cells continually adjust their inside and outside electrical charges. Normal levels of calcium ions, for example, are 20,000 times higher outside the cell than inside. Heart cells, using special voltage-sensitive calcium channels, can quickly upset this ratio, generating the spike of energy needed for a heartbeat. Through the controlled movement of ions across its membrane, the cell returns to its resting state and then recharges its battery to begin the next cycle.

• http://www.medicinenet.com/electrolytes/article.htm

Three types of Chemical Bonds

• Chemically combining of two or more atoms

1. Covalent Bonds

2. Ionic Bonds

3. Hydrogen bonds

These are not all the bonds but all we are going to cover.

Ionic Bond – valence electrons are TRANSFERRED from one ion to another!!!,

FK

Ionic Bonds

Drawing an Ionic Compound

1. Draw the Lewis Dot structure for the atoms.

2. Show the electron(s) transfering from one atom to another.

Ionic bondingIonic bonding involves 3 steps (3 energies) 1) loss of an electron(s) by one element,

2) gain of electron(s) by a second element,3) attraction between positive and negative

Ionic Bonds: One Big Greedy Thief Dog!

1). Ionic bond – electron from Na is transferred to Cl, this causes a charge imbalance in each atom. The Na becomes (Na+) and the Cl becomes (Cl-), charged particles or ions.

Ionic Bonds

One or more electrons from 1 atom are removed and attached to another atom, resulting in +ve(cation) and –ve(anion) ions which attract each other

Covalent Bonds

• One or more pairs of electrons are shared by two atoms

2.8 Covalent bonds join atoms into molecules through electron sharing

• A covalent bond results when atoms share outer-shell electrons– A molecule is formed when atoms are held together

by covalent bonds


Animation: Covalent Bonds

Covalent Bond

• Between nonmetallic elements of similar electronegativity.

• Formed by sharing electron pairs

• Stable non-ionizing particles, they are not conductors at any state

• Examples; O2, CO2, C2H6, H2O, SiC

when electrons are shared equally

NONPOLAR COVALENT BONDS

H2 or Cl2

2. Covalent bonds- Two atoms share one or more pairs of outer-shell electrons.

Oxygen AtomOxygen Atom Oxygen AtomOxygen Atom

Oxygen Molecule (O2)

http://www.usfca.edu/fac-staff/Courses/BIOL104_USF/104_Fall03_ppt/Text%20Chapter%2002/OxgnMol.swf



when electrons are shared but shared

unequally

POLAR COVALENT BONDS

H2O

Polar Covalent Bonds: Unevenly matched, but willing to share.

- water is a polar molecule because oxygen is more electronegative than hydrogen, and therefore electrons are pulled closer to oxygen.

Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons

C would like to N would like toO would like to

Gain 4 electronsGain 3 electronsGain 2 electrons

NaSodium atom

Transfer ofelectron

ClChlorine atom

NaSodium atom

Transfer ofelectron

ClChlorine atom

Na+

Sodium ionCl–

Chloride ion

Sodium chloride (NaCl)

+ –

2.9 Unequal electron sharing creates polar molecules

• Atoms in a covalently bonded molecule continually compete for shared electrons– The attraction (pull) for shared electrons is called

electronegativity– More electronegative atoms pull harder



• In molecules of only one element, the pull toward each atom is equal, because each atom has the same electronegativity



• Water has atoms with different electronegativities– Oxygen attracts the shared electrons more strongly than

hydrogen– So, the shared electrons spend more time near oxygen – The result is a polar covalent bond



• In H2O the oxygen atom has a slight negative charge and the hydrogens have a slight positive charge– Molecules with this unequal distribution of charges

are called polar molecules


(–) (–)

O

HH

(+) (+)

2.10 Hydrogen bonds are weak bonds important in the chemistry of life

• Some chemical bonds are weaker than covalent bonds

• Hydrogen, as part of a polar covalent bond, will share attractions with other electronegative atoms

– Examples are oxygen and nitrogen

• Water molecules are electrically attracted to oppositely charged regions on neighboring molecules

– Because the positively charged region is always a hydrogen atom, the bond is called a hydrogen bond


Animation: Water Structure

Hydrogen bond

WATER’S LIFE-SUPPORTING PROPERTIES


2.11 Hydrogen bonds make liquid water cohesive

• Hydrogen bonding causes molecules to stick together, a property called cohesion– Cohesion is much stronger for water than other liquids

– This is useful in plants that depend upon cohesion to help transport water and nutrients up the plant


2.11 Hydrogen bonds make liquid water cohesive

• Cohesion is related to surface tension—a measure of how difficult it is to break the surface of a liquid– Hydrogen bonds are responsible for surface tension


Animation: Water Transport

Water-conductingcells

Adhesion

Cohesion

150 µm

Directionof watermovement

2.12 Water’s hydrogen bonds moderate temperature

• Because of hydrogen bonding, water has a greater ability to resist temperature change than other liquids– Heat is the energy associated with movement of

atoms and molecules in matter– Temperature measures the intensity of heat

• Heat must be absorbed to break hydrogen bonds; heat is released when hydrogen bonds form


2.13 Ice is less dense than liquid water

• Water can exist as a gas, liquid, and solid– Water is less dense as a solid, a property due to

hydrogen bonding


2.13 Ice is less dense than liquid water

• When water freezes, each molecule forms a stable hydrogen bond with four neighbors– A three-dimensional crystal results– There is space between the water molecules

• Ice is less dense than water, so it floats


Liquid waterHydrogen bonds

constantly break and re-form

IceHydrogen bonds

are stable

Hydrogen bond

2.14 Water is the solvent of life

• A solution is a liquid consisting of a uniform mixture of two or more substances– The dissolving agent is the solvent– The substance that is dissolved is the solute


2.14 Water is the solvent of life

• Water is a versatile solvent that is fundamental to life processes– Its versatility results from its polarity– Table salt is an example of a solute that will go into

solution in water– Sodium and chloride ions and water are attracted to each

other because of their charges


Ion insolution

Saltcrystal

2.15 The chemistry of life is sensitive to acidic and basic conditions

• A few water molecules can break apart into ions– Some are hydrogen ions (H+)– Some are hydroxide ions (OH–)

– Both are extremely reactive

– A balance between the two is critical for chemical processes to occur in a living organism



• Chemicals other than water can contribute H+ to a solution– They are called acids– An example is hydrochloric acid (HCl)

– This is the acid in your stomach that aids in digestion

• An acidic solution has a higher concentration of H+ than OH–



• Some chemicals accept hydrogen ions and remove them from solution– These chemicals are called bases– For example, sodium hydroxide (NaOH) provides

OH– that combines with H+ to produce H2O (water)

– This reduces the H+ concentration



• A pH scale (pH = potential of hydrogen) is used to describe whether a solution is acidic or basic– pH ranges from 0 (most acidic) to 14 (most basic)– A solution that is neither acidic or basic is neutral

(pH = 7)


Acidic solution

pH scale

Battery acid

0

1

2

3

4

5

Lemon juice, gastric juice

Grapefruit juice, soft drink,vinegar, beer

Tomato juice

Rain water

Human urine

Saliva

Pure water

6

7

Human blood,tears

Seawater

8

9

10

11

12

13

Milk of magnesia

Household ammonia

Household bleach

Oven cleaner

Neutral solution

Basic solution

NEUTRAL[H+]=OH–]

Incr

easi

ngl

y A

CID

IC(H

igh

er c

once

ntr

atio

n o

f H

+)

14

Incr

easi

ngl

y B

AS

IC(L

ower

con

cen

trat

ion

of

H+)

Acidic solution Neutral solution Basic solution

2.16 CONNECTION: Acid precipitation and ocean acidification threaten the environment

• When we burn fossil fuels (gasoline and heating oil), air-polluting compounds and CO2 are released into the atmosphere– Sulfur and nitrous oxides react with water in the air

to form acids– These fall to Earth as acid precipitation, which is rain,

snow, or fog with a pH lower than 5.6

– Additional CO2 in the atmosphere contributes to the “greenhouse” effect and alters ocean chemistry


2.17 EVOLUTION CONNECTION: The search for extraterrestrial life centers on the search

for water

• An important question is, has life evolved elsewhere?– Water is necessary for life as we know it

• The National Aeronautics and Space Administration (NASA) has evidence that water was once abundant on Mars– Scientists have proposed that reservoirs of water

beneath the surface of Mars could harbor microbial life


August 1999 September 2005

New deposit

CHEMICAL REACTIONS


2.18 Chemical reactions make and break bonds, changing the composition of matter

• You learned that the structure of atoms and molecules determines the way they behave– Remember that atoms combine to form molecules– Hydrogen and oxygen can react to form water

2H2 + O2 2H2O


2.18 Chemical reactions make and break bonds, changing the composition of matter

• The formation of water from hydrogen and oxygen is an example of a chemical reaction

• The reactants (H2 and O2) are converted to H2O, the product– Organisms do not make water, but they do carry out

a large number of chemical reactions that rearrange matter

– Photosynthesis is an example where plants drive a sequence of chemical reactions that produce glucose


2 H2 O2 2 H2O

electron transferbetween atoms

creates

electron sharingbetween atoms

creates

ChemicalBonds

atomic number ofeach element

water

nonpolarcovalent bonds

(e)ions

(f) (g)

(h)

attraction betweenions creates

unequalsharing creates

can lead toexample is

equalsharing creates

has importantqualities due

to polarity and

have positivelycharged have neutral

have negativelycharged

number in outershell determines

formation of

number maydiffer in

number presentequals

(a)

Atoms

(b) (c)

(d)

atomic number ofeach element

have positivelycharged have neutral

have negativelycharged

number in outershell determines

formation of

number maydiffer in

number presentequals

(a)

Atoms

(b) (c)

(d)

electron transferbetween atoms

creates

electron sharingbetween atoms

creates

ChemicalBonds

water

nonpolarcovalent bonds

(e)ions

(f) (g)

(h)

attraction betweenions creates

unequalsharing creates

can lead toexample is

equalsharing creates

has importantqualities due

to polarity and

Potassium atomFluorine atom

You should now be able to

1. Describe the importance of chemical elements to living organisms

2. Explain the formation of compounds

3. Describe the structure of an atom

4. Distinguish between ionic, hydrogen, and covalent bonds

5. List and define the life-supporting properties of water

6. Explain the pH scale and the formation of acid and base solutions

7. Define a chemical reaction and explain how it changes the composition of matter


Documents

Name the levels of life from the smallest to the largest!!!