Physical and Chemical Properties and Changes

Physical and Chemical Properties and Changes

Physical Property

~  Definition: a characteristic of a substance that can be observed without changing it into another substance

~  Examples: color and texture, flexibility, freezing point, state of matter, luster, ability to conduct heat and electricity, attracted to a magnet, etc.

~  Identify some physical properties of silly putty

Chemical Property

~  Definition: a characteristic of a substance that describes its ability to change into different substances

~  To observe chemical properties of a substance, you must try to change it to another substance

~  Examples: flammability, ability to react with oxygen (rust vs. gold), ability to react with sulfur (silver tarnishing vs. gold)

~  Identify some chemical properties of a match

Physical Change

~  Definition: any change that alters the form or appearance of matter but does not make any substances in the matter into a different substance

~  A substance that undergoes a physical change is still the same substance after the change.

~  Examples: changes of state, dissolving, bending, crushing, breaking, chopping, filtration, distillation

~  Identify the physical change with the lava lamp and dissolving sugar (point out physical properties that are the basis for the changes)

Chemical Change

~  Definition: any change in matter that produces one or more new substances

~  Aka: chemical reaction

~  A chemical change produces new substances with properties different from those of the original substances

~  Examples: hydrogen peroxide into water and oxygen, rusting, burning methane, combustion, electrolysis, oxidation, tarnishing

~  Define flammability and reactivity

~  Identify the chemical change in the alka seltzer cannon and methane mamba (point out properties of original versus new substances)

Conservation of Mass

~  Matter is not created or destroyed in any chemical or physical change

~  Aka: Law of Conservation of Matter

~  Example: Methane + Oxygen à Carbon dioxide and water

Matter and Thermal Energy

~  Any time there is change, energy is involved

~  Temperature: the average kinetic energy of the particles in a substance

~  Thermal energy: the total PE and KE of the particles in a substance

~  Endothermic: energy in, a change in which energy is taken in, ex: melting

~  Exothermic: energy out, a change in which energy is released, ex: combustion