Bio 2 Chapter 2

Bio 2 Chapter 2

Matter

Multiple Choice

What is matter?

• Anything that takes up space and has mass

• The amount of mass that an object has

• A collection of atoms and molecules put together

Multiple Choice

What is a substance that can not be broken down into simpler substances by ordinary chemical means.

• Element

• Atom

• Molecule

• Compound

Elements

• Elements - Substance that can not be broken down into simpler substances by ordinary chemical means

• Every element has its own unique properties; Density, Solubility, melting point

• Only 94 naturally occurring

• Serve as building blocks of matter

• 6 elements are basic to life and make up 95% of organisms.; Carbon, hydrogen, nitrogen, oxygen, phosphorous, sulfur

Atoms

• Atoms - Smallest part of an element that displays properties of the element.

• Two letters create atomic symbol

• Atoms are made of subatomic particles; Protons, neutrons, electrons

• Protons, neutrons found in nucleus, electrons found inn electron shells

Multiple Choice

What represents the number of protons in an atom of a certain element?

• Atomic Number

• Atomic Mass

• Valence number

Atomic Number and mass number

• Atomic number - Number of protons in an atom of a certain element

• Unique to every element

• Also tells you the number of electrons

• Mass number - sum of protons and neutrons in the nucleus
  
  

• When an atom stands alone and not in the periodic table, the atomic number is written as a subscript to the lower left of the atomic symbol, the mass number is written in the upper left.

Atomic Number and Mass Number

• Be sure to use mass and not weight, weight changes according to the gravitational force of the body

• Atomic mass - average mass for all the isotopes of that atom

• Majority of carbon is carbon 12, so atomic mass is very close to 12.

Atomic Number and Mass Number

• Number of neutrons may vary in each element.

• Isotopes - atoms of each element that differ in the number of neutrons

• Carbon has 3 naturally occurring isotopes. 12, 13, and 14 are their mass numbers.

Multiple Choice

What do we use to organize all the different elements?

• A compass

• Mrs. Matuska's classroom

• The periodic table

• Washington D.C.

The Periodic Table

• Constructed by Dmitri Mendeleev

• Horizontal Rows - Periods

• Vertical Columns - groups

• Group 8: Noble gases

• Noble gases rarely react with other atoms

Radioactive isotopes

• Some isotopes decay and become other elements over time.

• Carbon-14 changes into Nitrogen 14.

• Carbon-14 releases various types of energy in the form of rays and subatomic particles.

• Isotopes can have low levels of radiation, and cause no help or harm to the environment

• Can have high levels of radiation, and cause damage to cells and organisms.

Electrons and Energy

• Protons and neutrons are in the nucleus, Electrons are circling around nucleus

• Many different ways to draw atoms.

• Bohr model; Draws electrons in different energy levels

• Electrons can move between energy levels.

Moving between energy levels.

• Energy is absorbed and electrons move to higher energy levels,

• Energy is released as they move back to their original energy level

• First energy level contains 2 electrons, then each level after contains 8, a level must be filled before moving to the next level

The Bohr Model

• Outermost shell is Valence shell

• Determines chemical properties

• Shell is complete when it hits the full number of electrons (one for 1, and 8 for each one after)

• Octet rule - Valence shell after first is complete at 8 electrons

• Noble gases generally do not react.

• Valence shell determines if an element gives up, accepts, or shares electrons to acquire eight.

Molecules and Compounds

• Molecule - two or more of the same type of atoms bond together.

• Compound - Molecule containing elements of different elements

• In biology we mainly speak of molecules, molecule and compound are generally used interchangeably.

Formula

• Formula - Number of each kind of atoms in a molecule

• Glucose

• Electrons possess energy, as do bonds between atoms. Organisms are directly dependent on this bond energy. Break down glucose to obtain energy.

Multiple Choice

How many electrons can go into the first valence shell of an atom?

• 2

• 8

• 6

• 10

Ionic Bonding

• Sodium has 1 electron in its valence shell.

• Tends to donate electrons

• With that electron donated, the otermost shell then has 8 electrons

• Chlorine has 7 electrons in valence shell

• Chlorine tends to accept electrons ro make balanced valence shell.

NaCl

• Losing and gaining electrons causes a charge imbalance

• Na losing 1 electron creates Na+ and Cl gaining one electron creates Cl-

• Sodium has 1 more proton than it does electrons, Chlorine has 1 less proton than it does electrons, causing a charge imbalance

• Ionic bond - Attraction between negatively and positively charges ions

• Ion - charged particles

Covalent Bonding

• Covalent bond - Two atoms share electrons in a way that puts 8 electrons in each valence shell.

• Hydrogen is complete when its outermost shell has 2.

• Will give up its electron in presence of strong electron acceptor,

• Will become hydrogen ion H+

• Can also share with another atom to complete shell

• Hydrogens will generally share with another hydrogen atom

• Electron shells overlap, electrons are shared.

Covalent Bonding

• Atoms may share more than one pair of electrons

• Oxygen (O2)

• Double covalent bond

Nonpolar and Polar covalent bonds

• Nonpolar covalent bond - Sharing of electrons between two atoms is equal

• Some cases, one atom is able to attract electrons to a greater degree than the other

• The atom that attracted better has a greater electronegativity

• Polar covalent bond - electrons are not shared equally

• Water is polar. Oxygen atom is more electronegative than oxygen atoms

Chemistry of water

• The shape of a water molecule and its polarity result in the formation of hydrogen bonds.

• Hydrogen Bonds - caused by attraction of a slightly positive hydrogen to a slightly negativity atom in the vicinity.

Hydrogen Bonding

• Hydrogen atoms in one water molecule are attracted to the oxygen atoms in other water molecules.

• Hydrogen bonds are weaker than ionic or covalent bonds

• Multiple hydrogen bonds, however, are quite strong.

• Hydrogen bonds hold strands of DNA together

• Important properties of water are a result of hydrogen bonding

Properties of Water

• All living organisms are 70 - 90% water

• Without hydrogen bonding, water would freeze at -100 degree C and boil at -91 degrees C, which would make most of earth’s water steam.

Water has a high heat capacity

• Calorie - amount of heat energy needed to raise the temp of 1 g of water by 1 degree C.

• Other covalently bonded liquids require input of only about half this amount

• Hydrogen bonds in water absorb heat without temperature changing significantly.

Water has a high heat of evaporation

• All hydrogen bonds must be broken in order for water to boil

• Takes 540 Calories to convert 1 g of hot water to a gas.

Water is a solvent

• Water facilitates chemical reactions due to its polarity.

• Dissolves great number of substances, especially polar ones

• Solution - contains dissolved substances

• Solutes - dissolved substances

• When NaCl is put into water, negative ends of water molecules are attracted to sodium. Positive ends of the water molecules are attracted to the chloride ions. Chloride and sodium ions then separate in water.

Water Molecules are cohesive and adhesive

• Cohesion - ability of water molecules to cling to each other due to hydrogen bonding.

• A water molecule can form hydrogen bonds with at most four other water molecules

• Because of cohesion, water exists as a liquid under standard temperature and pressure.

• Apparent because water flows freely, yet water molecules do not separate.

Water Molecules are cohesive and adhesive

• Adhesion - ability of water molecules to cling to other polar surfaces

• Result of  water’s polarity

• Multicellular animals often contain internal vessels in which water assists transport of nutrients and wastes.

• Liquid portion of our blood, which transports dissolved and suspended substances about the body, is 90% water.

Water Molecules are cohesive and adhesive

• Cohesion and adhesion contributes to transport of water in plants

• Roots absorb water

• Water evaporating from leaves is replaces with water molecules from transport vessels

• Water is pulled up the roots by cohesion

Water Molecules are cohesive and adhesive

• Water molecules cling together at the surface, creating surface tension

• Surface tension - force between molecules in a liquid

• Makes it possible for humans to skip rocks

Multiple Choice

Which is more dense?

• Frozen water

• Liquid Water

• They have the same density

Frozen water is less dense than liquid water

• As water cools, molecules come closer together

• At 4 degrees, molecules begin to expand, then freeze.

• Ice floats on liquid water.

• If ice was more dense than water, large bodies of water would freeze solid.

Acids and Bases

• When water ionizes, it releases an equal number of hydrogen ions (H+) and Hydroxide ions (OH-)

Acidic solutions

• High H+ concentrations

• Acids - Substances that dissolve in water, releasing hydrogen ions.

• Acidity of a substance depends on how fully it dissociates in water.

• Hydrochloric acid, strong acid, dissociates almost completely

Basic solutions

• Low hydrogen ion concentration

• Bases - substances that take up hydrogen ions or release hydroxide ions.

• If NaOH is added to water, Hydroxide ions increase and hydrogen ions decrease.

pH scale

• Indicates acidity or basicity

• Ranges from 0-14

• pH of 7 represents a neutral state

• Below 7 is acidic

• Above 7 is basic

• As you move down the pH scale from 14 to 0, each unit is 10 times more acidic

Buffers and pH

• Buffer - Chemical or a combination of chemicals that keeps pH within normal limits

• Take up excess hydrogen or hydroxide ions