Changes Physical Reversible Irreversible Chemical EXAMPLES? The world around us (matter) is always in a a state of flux. All changes involve some form of energy transfer. Changes Physical Reversible Irreversible Chemical EXAMPLES? Atoms are constantly rearranging Cook an egg Eat food, gain energy, digest it poop Mountains come and go Grand Canyon –ice ages Weather systems hurricanes etc. Cooking Rusting Fireworks

Physical Changes Aluminum Aluminum Aluminum The internal composition of something does not change. It remains the same chemically. Examples: Ripping paper, crushing a can, cutting hair, breaking chalk, molding Play-Doh cracking an egg. Aluminum foil is made up of aluminum atoms. Tearing aluminum foil in half still results in aluminum atoms Rrip paper Rip open a bag of chips Rip student notebook Fake homework email from azzarra Pretend to cut somone’s hair Aluminum Aluminum

Two Types of Physical Changes Irreversible Physical Change: something that cannot be undone. For example, you cannot uncrack an egg or uncut hair. Reversible physical change: a change that can be reversed. Phase changes are reversible. Ice that melts can be refrozen.

Phase Changes are Physical Changes Whether solid in the form of ice, as a liquid or as a gaseous vapor, water is always H2O. Water always has a ratio of two hydrogen atoms to one oxygen atom regardless of the form it is in. Phet App: States of Matter O H Show water, show neon

EVAPORATION CONDENSATION Physical Changes DEPOSITION MELTING FREEZING GAS CONDENSATION LIQUID Physical Changes DEPOSITION MELTING FREEZING SOLID SUBLIMATION

Burn Burn Burn Play Ellie Goulding Song Burn students notebook

Something New forms at the Molecular Level Chemical Changes One or more substances changes into something new. The internal properties of a substance change. Example: Burning Paper (combustion in general), digestion of food, rusting, fireworks exploding, cooking an egg, any chemical reaction. Light sparkler Something New forms at the Molecular Level

Combustion of Steel Wool 4Fe+ 3O2---> 2Fe2O3 O O Fe Fe Fe Fe Fe + Fe  O O Fe Fe O O O O O O O O Burn Steel wool   2H2 + O2  2H2O Formation of water 2H2O  2H2 + O2 Electrolysis of water 4 iron atoms (4Fe) combine with 6 oxygen (3O2) atoms to form two units of iron oxide (2Fe2O3)

+  Electrolysis of Water 2H2O + electricity  2H2 + O2 Hoffman apparatus…show this 2 water molecules (2H2O) split into 4 hydrogen atoms (2H2) and 2 oxygen atoms (O2),

Hoffman Apparatus: Electrolysis Electrocuting water (H2O) causes its bonds to break and it separates into H2 and O2 This is a CHEMICAL CHANGE, something new forms. H2O + Electricity  H2 + O2 TheoryA Hoffman voltameter, or Hoffman apparatus, uses electrolysis to produce hydrogen and oxygen gasses from water. By passing a DC electric current through the water (with an electrolyte solute to improve conductivity), energy is put into the water – enough so that the chemical bonds within H2O are broken and it splits and reforms into H2 and O. The O then finds another O that split from another molecule of water and forms O2. Hydrogen gas (H2) forms as bubbles at the negative cathode and oxygen gas (O2) at the positive anode, so if the two electrodes are kept slightly separate, the two gasses can be collected separately and used for good, or evil, depending on personal preference.

CHEMICAL OR PHYSICAL CHANGE? Baking Soda and Vinegar Chemical or Physical Cooking an Egg Ripping Paper Lighting a Match C₃H₈O molecules evaporating Ice Melting Mixing Baking soda and vinegar Getting a suntan Show Video Talk about rockets https://www.youtube.com/watch?v=UclxSfPoapc

5 Clues a Chemical Change might have taken Place Transfer of Energy (temperature change…endothermic/exothermic reactions) Color Change (ex. Fruit changes color over time, this is a chemical change) Formation of a Precipitate (a solid particle when two solutions are mixed) Production of Gas (gas bubbles indicate a chemical change might have occurred) Production of an Odor (an egg rotting, smell of the atmosphere after a lightning storm) Lab 1) Endothermic and Exothermic Lab