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