Ch. 2: Energy Forms of Energy Energy: is the ability to do work or to produce change. Ex: lifting arm or melting snow. SI (International System of Units) expresses the unit of measure for energy in joules(J) 1 J is the amount of energy needed to lift an object weighing 1 newton (N) to a height of 1 metre. Forms of Energy 1) Thermal Energy: the energy that comes from the random motion of particles of a substance. Ex: melting snow, steam train, hot-air balloon 2) Mechanical Energy: Results from the speed of an object, its mass and its relationship to its surroundings. Ex: a rock held at different heights, wind energy, hydraulic energy, creation of a crater.

Properties affecting Thermal Energy Factor Factor variation Result Number of particles More particles Increased thermal energy Fewer particles Reduced thermal energy Temperature Higher temperature Lower temperature Both have the same temperature, but the second beaker contains twice the amount of thermal energy. 250 ml 50º C 500 ml

Radiant & Chemical Energy 3) Radiant Energy: contained in and transported by electromagnetic waves. Electromagnetic waves transport energy from one place to another. Quantity depends on wavelength and amount of radiation. Shorter the wavelength the more energy transported. Ex: light, UV rays in tanning, X- Ray images, radiation therapy 4) Chemical Energy: stored in the bonds of molecules. Energy in reserve. Amount is dependant upon strength & number of bonds. Stronger bonds contain more energy. Energy is released when the bonds are broken. Ex: burning a candle, combustion of gasoline in car, cellular respiration.

Energy Transformation and Transfer Energy transformation: is the changing of energy from one form to another. Ex: burning a log: chemical energy stored in wood is transformed to  radiant energy (light) and thermal energy (particle movement). Energy transfer: is the movement of energy from one place to another. Movement of energy from burning log to surroundings; heat. Heat: transfer of thermal energy from one place to another. Travels from place of higher temperature toward lower temperature. *Energy transfer and transformation can result in both chemical and physical changes.

3 Types of Physical Changes involving Energy 1. Phase Changes/Changes of State 3 states of matter: solid, liquid and gas The transformation from one state or phase to another. Ex: (freezing) H2O(s) ↔ H2O (l) (melting)

CHANGES OF STATES/PHASE CHANGES Phase changes: The change in thermal energy (addition or removal of heat) changes the forces of attraction causing the particles to move closer to, or further from, one another resulting in a change of state. 1) Melting/Fusion: Solid → Liquid Ex: Ice  water Freezing/Solidification: Liquid → Solid Ex. water  Snow flakes Vaporization (boiling & evaporation): Liquid → Gas Ex: water  steam

4) Condensation: Gas → Liquid Ex: Steam  water 5) Sublimation: Solid → Gas *The solid does not melt to liquid, Instead turns directly to gas. Ex. Dry Ice [CO2 (s)] to CO2 (g)] 6) Deposition: Gas → Solid The gas cools but skips condensation and turns directly to a solid. Ex: Snow, frost, hail Ex: Iodine vapour -> Solid Iodine

3. Deformation 2. Dissolution The creation of a solution by a solute dissolved in a solvent. Ex: sugar in water, carbon in iron. Normally involves the absorption or release of energy. When dissolution releases energy temperature When dissolution absorbs energy temperature ־ Dilution: Decreasing the concentration of a solution does not change the physical nature of the solution. 3. Deformation Changing the shape of a material. Some are reversible (stretching a coil), some are permanent (tearing a sheet of metal). Involves an energy transfer, usually more than one. Ex: jumping on a trampoline (mechanical to elastic which is a reversible deformation)

4 Types of Chemical Changes Involves the production of one or more new substances. One or more substances (reagents) react to make new substances (products) Bonds between reagents change and reform making new substances. Changes the nature and characteristic properties of matter. Law of conservation of mass: all matter is transformed none is created or destroyed, # of atoms remains constant. Telling difference between chemical and physical changes: -The release of a gas -Greater changes of heat -Generation of light -Change of colour -Formation of a precipitate –Change in mass

Chemical change: 2Na(s) + 2H20 (l) → 2NaOH (aq) + H2(g)

2.Decomposition 1. Synthesis The formation of a complex molecule from atoms or simpler molecules. Ex: H2 reacts with O2 to form H2O. Is a chemical reaction that either absorbs or releases energy. Reaction where 2 or more reactants combine to form a new product ( A + B = AB) Photosynthesis absorbs energy: 6CO2 + 6 H2O + energy C6H12O6 + 6O2 Utilizes radiant energy to form stored energy as glucose. 2.Decomposition The transformation of complex molecules into simpler molecules or into atoms. Is the opposite of synthesis. Reaction where a compound separates into two or more compounds or elements. (AB = A + B) The chemical energy of a molecule is released or transformed into other forms of energy. Ex: glycogen decomposing into glucose releases thermal energy, electrolysis of H2O uses energy

1. Synthesis Reaction: +  +  If you see mass, the ONLY thing you know is that a compound was made!!! 1. Synthesis Reaction: Makes a new substance Sign of a chemical change Increase in mass Ex. +  + 

2. Decomposition Reaction: Two or more substances produced Sign of a chemical change Decrease in mass Ex. If you see mass, the ONLY thing you know is that you started with a compound!  + + 

4. Precipitation 3.Oxidation Occurs when two solutions are combined and an insoluble or less soluble substance forms. Ex: when doing the Fehling reagent test for carbohydrates the presence of certain carbohydrates formed a precipitate. Requires very little energy. Is a chemical reaction involving oxygen in the air or a substance with similar properties to oxygen. Ex: iron rusting, banana ripening, fire, cellular respiration (opposite of photosynthesis). C6H12O6 + 6O2 6CO2 + 6 H2O + energy 4 Fe + 3 O2 2 Fe2O3 +energy Combustion is a form of oxidation that releases a large amount of energy.