chemistry chapter two. what is chemistry? chemistry- the study of matter, atoms and chemical...

ChemistryChapter Two

What is Chemistry?

• Chemistry- the study of matter, atoms and chemical reactions– Why?

• to understand how our cells are held together

• To understand the molecules and compounds making up the cell

Matter

• Matter- anything that occupies space and has a mass

– Mass- amount of matter an object has– Weight- pull of gravity on an object’s mass

• Weight can change, mass can not

• Volume- measure of the amount of space an object takes up

States of Matter

• Solid– Particles tightly

linked– Definite shape– Definite volume

• Ice, chair, book

• Liquid– Particles more

loosely connected– Definite volume– Shape varies

• Example- water, juice

• Gas– Particles not

linked at all– Volume fills

whatever container it occupies

– No shape• Example- oxygen,

helium

• Plasma

Atoms

• Atom- Basic building block of matter– Protons– Neutrons– Nucleus– Electron– Electron Cloud

(energy level) aka- electron shell

Nucleus

• Nucleus- dense area in center of atom– Houses both protons and neutrons– Gives atoms its mass

• Proton- positively charged particle

• Neutron- particle with no charge

Nucleus of Atom

Electron Cloud

• Vast area of atoms in which the electrons are found moving around

• Electron- negatively charged particle (e-)– Found in different energy levels of cloud

• 1st energy level- can hold max of 2 e-• 2nd and up energy level- can hold max of 8 e-

• Valence electron- number of e- in outermost level

Electron Energy Levels

Elements

• Atoms with the same number of protons are the same

• Pure substance made of only one type of atom

• Periodic Table- table used to organize all elements into rows and columns

Periodic Formulas

• Atomic number = number of protons• Neutral atoms- # protons = # electrons• Atomic mass= # protons + # neutrons• Number of neutrons= mass- # protons

– Example Argon Mass= 40, Protons= 18, Neutrons= 22 (40-18)

Need to Know Elements

• Carbon• Oxygen• Hydrogen• Phosphorus• Nitrogen

• Sodium• Magnesium• Chlorine• Potassium• Calcium

Atomic Bonding

• Two or more atoms combined by a chemical bond

• Compound- substance formed by combining two or more different elements

• Why bond?– Atoms want a complete outer shell (8

e-)– Will gain,lose or share e- to get to 8

– 8 is the magic number!!!!

Types of Bonds

• 1. Ionic- atoms will give or gain e-– Ion- charged

particle

– Gain e- gives negative charge

– Lose e- gives a positive charge

• 2. Covalent- atoms will share e-– Weaker bond

because neither atom is strong enough to take e-

Van der Waals Forces

• In covalent bonds, some atoms have a stronger pull on the e-, so sharing is unequal

• This creates areas of positive and negative charges across the neutral molecule– Opposite charges

then are attracted to each other

Energy

• Energy- ability to do work or cause change

• Free energy- energy available to do work

Chemical Reactions

• Reactants Products

• Reactants- atoms or compounds to start reaction

• Products- atoms or compounds that you end up with

Cont.

• Reactants and products are represented by atomic symbols and numbers– Number of atoms must be same on

both side

– Example- 2 H + O H2O

Cont.

• Arrows indicate direction of reaction

• indicates reaction is occurring in both directions

• Activation energy- amount of energy needed to start a reaction– Every reaction has different amount

of activation energy

Adjusting Reaction Time

• Catalyst- substance that lowers activation energy

– Usually an enzyme

How Enzymes Work

• Each has specific shape– “Lock and Key”

• Substrates (reactants)- bind to active site– Enzyme release

product because it no longer fits

Factors Effecting Enzymes

• pH - only function in small range of pH

• Temperature- function best within a range

• Concentration

• Each will vary depending upon enzyme

Transfer of energy

• Transfer of energy (two types)

– Exergonic- releases energy

– Endergonic- absorbs energy

Reduction-Oxidation Reactions (Redox)• Redox Reaction- energy transfer

that includes a transfer of e-• OiL RiG

– Oxidation Loses

– Reduction Gains

Mixtures

• Materials made of two or more substances that are physically mixed together, not chemically

• Three Types of Mixtures– Solution– Suspension– Colloid

Solutions

• One or more substances equally distributed in another

• Parts of Solution– Solute-substance that is dissolved

– Solvent- substance doing the dissolving

Solutions cont.

• Concentration- amount of solute added to set amount of solvent

– Examples- salt water, blood plasma

Suspensions

• A mixture of water and particles that do not dissolve in water, but break into smaller pieces– Example, finger

paint, oil and water

Colloid

• Substance evenly distributed into another

• Can exist in solid, liquid or gas forms– Particles much smaller than suspensions

Aqueous Solution

• Specific type of solution in which water is always the solvent

• Water- known as universal solvent– All organisms

need water

Properties of Water

1. Water is bent2. Polarity3. Hydrogen bonds4. Cohesion5. Adhesion

Polarity

• Unequal sharing of electrons– Oxygen is much

larger so it steals e-

– Oxygen negative charge

– Hydrogen positive charge

Hydrogen Bonds

• Special type of bond that is formed between two different water molecules– Opposites are

attracted together

• Cohesion- attractive force between same particles

– Example- water beading, bugs walking on water

• Adhesion- attractive force between unlike particles– Ex: meniscus; straw level– Also called capillary action-

movement against gravity

Other Properties

• Freezing/melting point-0ºC

• Vaporization point- 100ºC

• Density- varies by temperature (most dense at 4ºC)

The pH Scale

• What is pH?• Dissociation of water- when water

molecules break apart to form H+ ions and OH- ions

• pH is the measure of the amount of H+ ions in a solution

• Sometimes H+ will bond with H2O to form hydronium (H3O+)

Acid Vs. Base

• Hydroxide ion- the OH- ion

• Hydronium ion- the H3O+

• Acid- solution that has more H+ or H3O+ ions

• Base- solution that has more OH- – Alkaline- another word for base

solutions

The Scale

• pH scale ranges from 0-14

– Under 7= acidic

– 7= neutral (equal H+ and OH- ions)

– Above 7= basic

• Scale is logarithmic– Means every 1 number change is

actually = to 10 times

– Example-• 7-8= 10x• 7-9=100x• 7-10= 1000x

pH of common items

Regulating pH

• Buffers- substances that neutralize small amounts of acids and bases

– Important biologically for reactions to occur and to maintain homeostasis