-Used to identify substances and can be observed WITHOUT changing the identity (chemical composition) of the substance
Examples:
Melting Point-solid🡪liquid (0o C/32 o F for water)
Boiling Point-liquid🡪gas (100 o C/212 o F for water)
Density-relationship between mass and volume (Density=Mass/Volume)
Less dense substances float on top of more dense substances
Color-be careful with this one.
Magnetism-is it attracted to magnets
Conductivity-does it transfer heat and/or electricity
Hardness-can be tested with a scratch test
-used to identify substances and can be observed only when the identity (chemical composition) of the substance IS CHANGED
Examples:
Ability to burn-reacting quickly with oxygen to change a substance
Ability to rust-reacting slowly with oxygen to change a substance
pH-(potential Hydrogen) a scale (from 0-14) that tells a relative concentration of Hydrogen ions in a solution. This determines how much of an acid or base a substance is.
-after the change you still have
THE SAME SUBSTANCE
Indicators of a physical change:
Change in State of Matter
melting, freezing, condensing, evaporating, sublimating (change from solid directly to gas with no liquid phase)
Change in Size or Shape
cutting/tearing, stretching, dissolving
-solute-the substance being dissolved
-solvent-the substance doing the dissolving (usually water).
-solution-homogeneous mixture made of solute and solvent
-after the change you have a
A DIFFERENT SUBSTANCE
Indicators of a chemical change:
UNEXPECTED Color Change- ex: two clear liquids mixing to get a pink liquid (non-ex: adding food coloring is physical).
UNEXPECTED Temperature Change- ex: 2 room temperature liquids mix and get hot or cold (non-ex: heating water on the stove is physical)
Formation of a precipitate-when 2 solutions combine to form a solid substance
UNEXPECTED Gas formation- ex: mixing a liquid and a solid and getting bubble (non-ex: boiling water is physical change)
Change in smell