Chemical and Physical Change The Nature of Changes in Matter

Types of Changes : Physical Change The fundamental particles stay the same. Small change in energy Evaporating, Dissolving, Melting, Freezing Liquid water = H2O Ice = H2O Chemical Change Nuclear Change

Types of Changes : Physical Change The fundamental particles stay the same. Small change in energy Evaporating, Dissolving, Melting, Freezing Liquid water = H2O Ice = H2O Chemical Change A change in the bonds of a compound. New compound has its own properties. Medium change in energy Produces light, instant heating or cooling AlCl3  AlF3 Nuclear Change

Types of Changes : Physical Change The fundamental particles stay the same. Small change in energy Evaporating, Dissolving, Melting, Freezing Liquid water = H2O Ice = H2O Chemical Change A change in the bonds of a compound. New compound has its own properties. Medium change in energy Produces light, instant heating AlCl3  AlF3g or cooling Nuclear Change Create a new element. Releases radiation. Huge change in energy H + Proton = He

Kinetic Molecular Theory All matter is made of particles Smallest particles of matter are constantly moving Smallest particles = Elements and Compounds

Why Do Chemical Reactions Occur Explained by the kinetic molecular theory The random motion of particles results in collisions between the particles

collision-reaction theory Collision-reaction theory: Explains when these collisions result in chemical reactions 1) Orientation: Has to collide the right way 2) Energy: Needs enough energy to break bonds Orientation + Energy = rearrangement of particles

Chemical Reactions Chemical Reaction = Chemical change Evidence of Chemical Reactions Evidence Description and Example Color Change Final product is a different color then the starting material

Chemical Reactions Chemical Reaction = Chemical change Evidence of Chemical Reactions Evidence Description and Example Color Change Final product is a different color then the starting material Odor Change Final product has a different odor then the starting material

Chemical Reactions Chemical Reaction = Chemical change Evidence of Chemical Reactions Evidence Description and Example Color Change Final product is a different color then the starting material Odor Change Final product has a different odor then the starting material State Change Final product may be a different phase than the starting material

Chemical Reactions Chemical Reaction = Chemical change Evidence of Chemical Reactions Evidence Description and Example Color Change Final product is a different color then the starting material Odor Change Final product has a different odor then the starting material State Change Final product may be a different phase than the starting material Energy Change Heat, energy, sound, or light energy is either released (exothermic reaction) or absorbed (endothermic)

Chemical Reactions What if there is no obvious evidence of Chemical Reactions May require a chemical analysis (diagnostic test) if no observable change occurred

Conversion of Mass in Chemical Change Conservation of mass: The mass of the reactants is equal to the mass of the products Law of Conservation of Matter: Matter cannot be created or destroyed. If you start with 12.3578g your will finish with 12.3578g

Showing the conservation of mass in an equation Conservation of Mass: Next class