Chemical Reactions And Solutions, Solutes Types of Chemical Reactions And Solutions, Solutes & Solvents

Changes in Matter There are two categories of changes of matter. 1. A Physical Change is a process that does not change the chemical make-up in a substance. The only change is in size, color or state of the substance. 2. A Chemical Change does involve a change in the chemical make-up of the substance. After the change, it no longer has the same properties.

In any change, physical or chemical, some kind of energy must be applied to the substance in order for the change to occur.

Examples of Physical Changes Breaking Glass Separating rocks from sand Evaporating water Freezing popsicles Slicing bread Making chocolate milk Whipping cream

Examples of Chemical Changes Baking a cake Burning a candle Striking a match Garbage rotting Bread molding Plants making oxygen Frying an egg Bleaching your hair

Properties of Matter Physical Properties are characteristics that can be observed without changing the chemical make-up of the substances. Examples: Mass Weight Density Viscosity Ability to conduct heat Freezing Point Boiling Point Magnetism Color, Size, Shape, Odor & Hardness

Chemical Properties cannot be observed when looking at the substance Chemical Properties cannot be observed when looking at the substance. It shows up when the substance interacts with something else. Examples: Charcoal combines with oxygen, during burning, to form carbon dioxide. When iron combines with oxygen in air, the metal rusts. (Corrosion, the ability to rust) Sodium chloride & chlorine make table salt.

Chemical Reactions A chemical change: any change in which a new substance is formed. Evidence of a Chemical Change: Release of energy as heat Release of energy as light Change in color Formation of a gas Change in odor…

Types of Chemical Reactions Neutralization: Acid(H) + Base(OH)  salt + H(OH) Combustion: AB + oxygen  CO2 + H2O Synthesis: A + B  AB Decomposition: AB  A + B Single displacement: A + BC  AC + B Double displacement: AB + CD  AD + CB Be Aware that there are 6 types, however we are going to focus on Synthesis, Decomposition, Single Displacement and Double Displacement.

Synthesis Reactions A + B  AB where A and B represent elements Synthesis reactions are also known as FORMATION reactions. Two or more reactants (usually elements) join to form a compound. A + B  AB where A and B represent elements The elements may form ionic compounds, like… Sodium metal and chlorine gas combine to form sodium chloride. 2Na + Cl2  2NaCl Sodium added to chlorine gas Note the reactant side of equation: E + E = Synthesis

Synthesis Reactions Skinny Bird plus Worm yields Fat Bird

SYNTHESIS REACTION (iron + sulphur): Synthesis Reactions OTHER EXAMPLES… Elements that form ionic compounds: Magnesium metal reacts with oxygen gas to form magnesium oxide. 2Mg + O2  2MgO 2. Elements that form covalent compounds: Nitrogen gas and oxygen gas join to form dinitrogen monoxide. 2N2 + O2  2N2O SYNTHESIS REACTION (iron + sulphur): http://www.youtube.com/watch?v=A5H6DVe5FAI

Decomposition Reactions Decomposition reactions are the opposite of synthesis reactions. A compound breaks down into two or more products (often elements). AB  A + B where A and B represent elements 1. Ionic compounds may decompose to produce elements, like the following: Table salt, sodium chloride, can be broken down into sodium metal and chlorine gas by melting salt at 800ºC and running electricity through it. 2NaCl  2Na + Cl2 Reactant side: C = Decomposition

Decomposition Reactions Egg yields Shell + Baby Turtle

Decomposition Reactions 2. Covalent compounds may decompose into elements, like the following: By running electricity through water, the water molecules decompose into hydrogen and oxygen gases. 2H2O  2H2 + O2 DECOMPOSITION REACTION: http://www.youtube.com/watch?v=NddwtXEA_Ak

Single Replacement Reactions Single replacement reactions replace one element from a compound with another element. A compound and an element react, and the element switches places with part of the original compound. A + BC  B + AC where A is a metal, or A + BC  C + BA where A is a non-metal Reactant side: E + C = Single Replacement

Single Replacement Reactions

Single Replacement Reactions 1. When A is a metal: Aluminum foil in a solution of copper(II) chloride produces solid copper and aluminum chloride. 2Al + 3CuCl2  3Cu + 2AlCl3 2. When A is a non-metal: When fluorine is bubbled through a sodium iodide solution, iodine and sodium fluoride are produced. Fl2 + 2NaI  I2 + 2NaF SINGLE REPLACEMENT: http://www.youtube.com/watch?v=hKtynbVtMKc

Double Replacement Reactions Double replacement reactions swap elements between 2 compounds that react together to form two new compounds. Two compounds react, with elements switching places between the original compounds. AB + CD  AD + CB Reactant side: C + C = Double Replacement

Double Replacement Reactions Fathead Black hat + Thin head White hat Yields Fathead White hat + Thin head Black hat.

Double Replacement Reactions Two solutions react to form a precipitate (solid) and another solution. Ionic solution + ionic solution  ionic solution + ionic solid. AB + CD  AD + CB When potassium chromate and silver nitrate react, they form a red precipitate, silver chromate, in a solution of potassium nitrate. K2CrO4 + 2AgNO3  Ag2CrO4 + 2KNO3 silver chromate DOUBLE REPLACEMENT: http://www.youtube.com/watch?v=opY3FLrPTa4

SUMMARY OF REACTIONS

Easy way to recognize reaction type:

ENERGY OF CHEMICAL REACTIONS Chemical reactions always involve a change in energy. Energy is neither created nor destroyed so it is absorbed or released in chemical reactions. ENDOTHERMIC REACTIONS Chemical Reactions in which energy is ABSORBED are endothermic. Energy is required for the reaction to occur. Examples are adding heat or electrical energy. EXOTHERMIC REACTIONS Chemical reactions in which energy is RELEASED are exothermic. Energy is stored in bonds & makes product feel hot.

Mixtures A mixture is a combination of 2 or more substances blended together without a chemical reaction. In a mixture… Each substance keeps its own properties . There is no chemical reaction. There is no repeated chemical make-up or chemical formula. Substances can be separated. 2 Types of Mixtures: Heterogeneous & Homogeneous

Kinds of Mixtures: A Heterogeneous mixture is a mixture in which the particles are not spread evenly throughout.

2 types of Heterogeneous Mixtures A Suspension Particles are large enough to be seen by eye or with microscope. Looks cloudy Particles will settle with gravity Can be separated out with filter paper

A substance microscopically dispersed throughout another substance. A Colloid: A substance microscopically dispersed throughout another substance. Particles won’t settle out with gravity. Can produce the Tyndall Effect:    For example, light being shined through water and milk. The light is not reflected when passing through the water because it is not a colloid. It is however reflected in all directions when it passes through the milk, which is colloidal. Examples of Colloids: Cheese, lava, paints, milk, whipped cream, smoke, fog.

The other type of mixture is a Homogeneous Mixture. It is a mixture in which particle of one substance are spread evenly throughout the other substance. Examples: Tea, root beer, vinegar, and lemon juice without pulp.

A solution is a homogeneous mixture with very tiny particles of a substance spread evenly throughout. The particles won’t settle out over time and can’t be filtered out. It is basically two substances that are going to be combined. The Solute is the substance to be dissolved. The Solvent is the one doing the dissolving. The Universal Solvent is Water.