Physical and chemical changes. Physical Property: A characteristic of that can be measured without...
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Transcript of Physical and chemical changes. Physical Property: A characteristic of that can be measured without...
Physical and chemical changes
• Physical Property: A characteristic of that can be measured without changing the chemical composition of a substance.
• Ex. Color, shape, size, density, melting point, boiling point, hardness, conductivity, malleability, ductility, state
Slide 8 of 10
• Physical change: a change which does not change the identity of the substance
• Ex. Boiling, melting, changing shape, mixing, freezing, dissolving
• Chemical change: A change where a new substance is formed from other substances, and has new properties
• Burning O2 and H2 gives off H2O and energy
• Chemical property: A characteristic of a substance which indicates whether it can undergo a specific chemical change
• Ex. Flammability, reactivity, or non-reactivity
Signs of a Chemical Change
• color change, • formation of a
precipitate, • gases given off, • energy change-
heating up or cooling down, light,
Signs of a reaction
• Precipitate: substance formed when a solid forms out of two liquids
Energy change
• Endothermic: chemical reaction that absorbs energy or heat
• Exothermic: chemical reaction gives off energy or heat
Exo vs. endo
Law of conservation of mass
• Law of Conservation of mass: mass of all substances before a chemical reaction is equal to the mass of all substances after the reaction
• •Extensive physical
• –Depend on the amount of the material present (ex. mass, length, & volume)
• •Intensive physical
• –Does not depend on the amount of material present (ex. density, boiling point, ductility, malleability, color)
Boiling Point
• Boiling point- Temperature at which vapor pressure overcomes atmospheric pressure.
• Does Water always boil at 100ºC
• Why or why not?
• What would it do in space?