Solids Liquids And Gases

Solids, Liquids, Gases

Tangerines, snakes and fireflies “Oh My” 

Tangerines = Solid

  

Snakes = Liquid

   

Fireflies = Gases

• • • •



A Molecular View of Water

All matter is made of atoms. atoms Elements are made of only one kind of atom. There are ~90 naturally occurring elements. Water is an example of a compound– compound a pure substance made of atoms of 2 or more elements joined together chemically in fixed proportions.

Molecules • The smallest part of a pure substance that still has all of its properties is called a molecule. molecule • Atoms within molecules are joined together by chemical bonds. bonds • One molecule of water is made of 2 hydrogen atoms bonded to 1 oxygen atom, or H2O. • A molecule of ammonia (NH3) will always be made of 1 nitrogen atom & 3 hydrogens

The Electrical Nature of Matter • How do bonds form? • Everyone experiences the electrical nature of matter. – Socks that stick together in the clothes dryer – Walking across a rug and then touching someone and getting shocked

• Summary of electrical properties of matter: – Like charges repel – Opposite charges attract

Causes of positive & negative charges • Atoms are neutral – Nucleus has positively-charged protons and neutrons with no charge at all – Orbiting the nucleus are an equal number of negatively-charged electrons that cancel-out the charge of the protons

• Attractions between the oppositely-charged particles hold the atoms together • Attractions between the + charged particles in one atom and the - charged particles in another atom hold multiple atoms together to form molecules

Ions & Ionic Compounds • Molecules are one type of compound • Compounds made of electrically-charged atoms or groups of atoms are ionic compounds. compounds • Ionic compounds have no net electrical charge • Ex: Na Cl (sodium chloride) had = numbers of Na+ and Cl - ions arranged in a 3-D crystal • •

Ions in Solution • When ionic cmpds. are dissolved in water, the ions separate (disassociation) disassociation and spread throughout the water. • Writing the ionic formula NaCl with the symbol (aq) after it shows that it’s dissolved in water (aqueous) aqueous solution • The + ion in the cmpd. is called the cation (Na+) and the – ion is called the anion  (Cl-). – Ex: CaCl2, AgCl, FeO  

Writing Ionic Formulas • Ions can be single atoms, like a sodium cation (Na+) or a group of bonded atoms like an ammonium cation (NH4+). • When an ion is made of more than one atom, it is a polyatomic ion. • When you write a compound formula, you always write the cation’s symbol first and the anion’s symbol second. • In a correct formula, formula the # of + & - ions will be equal, making the net charge of the compound zero.

Writing Ionic Formulas • Polyatomic ions formulas have one main difference: w/ more than one ion, they must be put in ( ), with a subscript to show how many ions there are. – Ca(NO3)2

• The written names of ionic cmpds. have two parts: cation + anion. • Many ionic cmpds.’ cation names are the same as their original elements’. • Single-atom anions have the ion name w/the suffix –ide on the end. • Ex: KF is potassium fluoride •

Investigating the Cause of the Fish Kill

Solubility of Solids • Could something dissolved in the Snake river have caused the fish kill? • To know whether or not it could have caused a problem, it is necessary to know about how solutions form and what affects them.

Factors Affecting Solubility (How much of a solute will dissolve in a solvent)

“A covalently bonded substance typically disperses in the solvent as individual molecules, while an ionic substance usually dissolves as individual ions among one or more solvent molecules.” Basic Chemistry

Temperature • Gases in water: water As temperature increases, the solubility of a gas in water decreases. • Solids in liquids: liquids Solubility usually increases when the temperature increases, with some exceptions. (?) 

Pressure • Henry’s Law: Law the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid. – Ex: If the partial pressure of the gas above the liquid is doubled, the solubility of the gas in the liquid is doubled; if the partial pressure is halved, then the solubility is also halved. – Effervescence: Effervescence the rapid escape of a gas from the liquid in which it is dissolved 

Properties • Many ionic compounds dissolve readily in water because of water’s polarity. (Adhesion) • Ionic compounds do not dissolve well in non-polar compounds, because their own + and – ions are more strongly attractive than a neutral molecule. • General rule: “Like dissolves like”.

If the solubility of a gas in water is 0.77g/L at 3.5 atm of pressure, what is its solubility (in g/L) at 1.0 atm of pressure and a constant temperature of 25° C? S 1 = S2 

P1



P2

S2 = 0.77 g/L X 1.0 atm

 

3.5 atm

   

= 0.22g/L

Factors Affecting Rate of Dissolution (How quickly solutes dissolve in solvents)

Particle size • Smaller particles of solute expose a greater total surface area to the solvent than larger particles. • The greater the surface area exposed, the more quickly a solute dissolves.

A Stirring tribute: • Stirring a solution creates more opportunities for undissolved particles of solute to come into contact with solvent molecules. 

Getting energized: • Raising the temperature increases the rate of solubility by increasing the kinetic energy of the solute and solvent particles. • The greater their kinetic energy, the more opportunities they have to collide and interact. • The higher the temperature, the more quickly the solute will dissolve.

Concentration of Solutions • ConcentrationConcentration a measure of the amount of solute in a given amount of solvent or solution • “Dilute” means that there is just a relatively small amount of the solute in a solvent. • “Concentrated” means that there is a relatively large amount. • A solution that is saturated is holding all of the solute that it can hold at that temperature.

Molarity • Molarity- the number of moles of solute in one liter of solution. • Ex: a 1M solution of NaOH contains 1 mole of NaOH in every liter of solution • Molarity (M) = amount of solute (mol) mol volume of solution (L) • 

• You have 3.50 L of solution that contains 90.0g of NaCl. What is the molarity of the solution? • Mass of solute = 90.0 g NaCl • Volume of solution = 3.50 L • Molar mass of NaCl = 58.44 g/mol  90.0g NaCl x 1.00 mol NaCl = 1.54 mol NaCl 58.44g NaCl    

1.54 mol NaCl = 0.0440 M NaCl 3.50 L of soln.

Molality

• Molality is the concentration of a solution expressed in moles of solute per kilogram of solvent. • 1 mol of NaOH dissolved in 1 kg of solvent is a 1molal soln. • molality (m) = moles solute (mol) mol mass of solvent (kg) kg  0.500 mol NaOH = 0.500m NaOH  1kg H20 



• Mass of solute = 17.1 g C12 H22 O11 • Mass of solvent = 125 g H20 • Molar mass of C12 H22 O11 = 342.34 g/mol • Unknown = molal concentration of C 12 H22 O11 

17.1g C12 H22 O11 x 1mol C12 H22 O11 = 0.0500

    

•

342.34g C12 H22 O11

mol

C12 H22 O11 125gH2O/1000g/kg= 0.125 kg H2O 0.0500 mol

STOP AND THINK

?

Definition (in own words) Examples (in own life)

Situation s (in own life)

Nonexamples (in own life)

SOLUTIONS

Careers

Situations (in rest of world)

Skills

Characteristics