3 Does a chemical reaction take place when one substance dissolves in another? No, dissolving is a physical change because no new substances are formed. When one substance dissolves in another, the resulting mixture is called a solution.
4 Some Definitions A solution is a _______________ - Mixture of 2 substances in one phase - Composed of a solvent and solute (can be more than one) HOMOGENEOUS
5 Parts of a Solution Substance dissolved Present in smaller amount Dissolves the solute Present in greater amount Determines the state of the solution (solid, liquid, or gas) Solute + Solvent = Solution (Homogeneous mixture) Solute Solvent
6 The solute breaks up into tiny particles that spread evenly throughout the solvent. In a solution of sugar water, sugar is the solute, and water is the solvent.
7 Are all solutions liquids? Many types of solutions are possible. Let’s talk about a few examples…. No! With your shoulder partner, think of solutions that are not liquids and be ready to share with the class your examples..
8 Alloy - a mixture done by the melting of two or more metals
9 How do I get solutes to dissolve faster in solvents? Ex. Sugar in iced tea? With your shoulder partner answer the question and be ready to share with the class…..
10 How do I get solutes to dissolve faster in solvents? Ex. Sugar in iced tea? Stirring Increase temperature of solvent Grind the solute to make it smaller Fresh solvent contact and interaction with solute Greater surface area, more solute-solvent interaction Faster rate of dissolution at higher temperature
12 The Polarity of Water Water has a simple molecular structure. Composed of one oxygen atom and two hydrogen atoms. Each hydrogen atom is covalently bonded to the oxygen via a shared pair of electrons.
13 Electronegativity Ability of an atom to attract electrons to itself while bonding to another atom Looking at water, which element has a higher electronegativity? OXYGEN
14 Since oxygen has a higher electronegativity than hydrogen: Electrons in molecule get closer to oxygen than with hydrogen The oxygen side has a slight or partial negative charge The hydrogen side has a slight or partial positive charge.
15 What does this do to the water molecule???? The partial positive and negative ends of the molecule make it a “polar” molecule There is an uneven distribution of electron density in the molecule
16 Hydrogen bond: Electrostatic attraction between partial positive charge near hydrogen atoms and partial negative charge near oxygen atom Weak bonds Non-covalent bonds Effective solvent https://www.youtube.com/watch?v=PVL24HAesnc
17 Dissolving process in water Na + Cl - When particles of the solute are completely dispersed and surrounded by particles of the solvent, this process is called SOLVATION.
18 Na + Cl - For water: POLAR-POLAR For NaCl (s): ion-ion For hydrated ion: Ion-polar The separation of the ions in an ionic compound (usually by dissolving water) is called DISSOCIATION
19 “Like dissolves like” –Polar dissolves in polar and ionic Ex. Salt and Water, sugar and water –Non-polar dissolves in non-polar Ex. oil and soap
20 Definition: The maximum amount of solute that will dissolve in a given amount of solvent at a specified temperature and pressure. Soluble- the solute can be completely dissolved in the solvent Insoluble- the solute cannot be dissolved in the solvent. In fact, it separates completely. SOLUBILITY
21 Miscible vs. Immiscible When two liquids completely mix they are said to be miscible. When two liquids do not mix they are said to be immiscible.
22 The physical process of converting an atom or a compound into ions by adding or removing electrons. Usually done by a solvent in a solution. IONIZATION
23 How do we know ions are present in aqueous solutions? If the solution conducts electricity it is called an ELECTROLYTE it is called an ELECTROLYTE Aqueous Solutions (water is the solvent)
24 Types of solutes Na + Cl - Strong Electrolyte - 100% dissociation, all ions in solution high conductivity
26 Aqueous Solutions Some compounds dissolve in water but do not conduct electricity. They are called NONELECTROLYTES. Examples include: sugarethanol ethylene glycol Examples include: sugarethanol ethylene glycol
27 Types of solutes sugar Non-electrolyte - No dissociation, all molecules in solution no conductivity
28 Electrolytes in the Body Carry messages to and from the brain as electrical signals Maintain cellular function with the correct concentrations electrolytes Make your own 50-70 g sugar One liter of warm water Pinch of salt 200ml of sugar free fruit squash Mix, cool and drink
29 Definitions Solutions can be classified as saturated or unsaturated. A saturated solution-Contains the maximum quantity of solute that dissolves at that temperature. An unsaturated solution- Contains less than the maximum amount of solute that can dissolve at a particular temperature
30 Definitions SUPERSATURATED SOLUTIONS contain more solute than is possible to be dissolved Supersaturated solutions are unstable. The supersaturation is only temporary, and usually accomplished in one of two ways: 1.Warm the solvent then cool the solution 2.Evaporate some of the solvent. http://www.youtube.com/watch?v=XSGvy2FP fCw
31 Solubility Curves 1. What is the solubility of KNO 3 at 40°C? ____________ 2. What is the solubility of NaNO 3 at 60°C? ____________ 3. At what temperature can 45 grams of HCl be dissolved in 100 grams of water? ____________ 4. At what temperature can KNO3 and NaNO3 have the same solubility? ____________
33 Solubility Curves 1. What is the solubility of KNO 3 at 40°C? ____________ 2. What is the solubility of NaNO 3 at 60°C? ____________ 3. At what temperature can 45 grams of HCl be dissolved in 100 grams of water? ____________ 4. At what temperature can KNO3 and NaNO3 have the same solubility? ____________ 65-66 grams 125 grams 90°C 67-68°C
34 Supersaturated Sodium Acetate Supersaturated Sodium Acetate One application of a supersaturated solution is the sodium acetate “heat pack.”One application of a supersaturated solution is the sodium acetate “heat pack.”