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Chemistry
Acids and Bases

What are some examples of chemical and physical changes?

Answer

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October 12, 2016 12:42PM

Physical Changes

  • Change of state (such as from solid to liquid or from gas to liquid)
    • Specific examples of state change include water freezing, alcohol evaporating and dry ice (solid carbon dioxide) subliming
  • Absorption of water into a towel
  • Crumpling a piece of paper
  • Pulling copper into a thin wire - a change of shape, but not a change of composition
  • Cutting a material such as wood
  • Tearing a piece of tin foil
  • Breaking glass
  • Deflating a basketball
  • Mixing different solids (such as solid sulfur and iron filings)
  • Inflating a volleyball
  • Cloud forming in the sky

Chemical changes

  • Burning a log of wood
  • Mixing an acid with a base, producing water and a salt.
  • Photosynthesis - a process in which carbon dioxide and water are changed into sugars by plants.
  • Cracking heavy hydrocarbons to create lighter hydrocarbons (part of the process of refining oil).
  • Cooking examples: popcorn, cake, pancakes, and eggs
  • Oxidation examples: rust or tarnishing
  • Combustion
  • Mixing chemicals
  • Rotting of fruit
  • Cooking rice
  • Explosion of fireworks
  • Tarnishing silver
  • Lighting a match
  • Chewing/digesting food
  • Rusting nail
  • Burning gas in a stove
  • Oxidizing food for energy
  • Roasting a marshmallow
  • Adding food coloring to icing
  • Frying an egg
  • Burning a magnesium strip

The following can indicate that a chemical change took place, although this evidence is not conclusive:

  • Change of color (for example, silver to reddish-brown when iron rusts)
  • Change in temperature or energy, such as the production (exothermic) or loss (endothermic) of heat
  • Change of form (for example, burning paper)
  • Light, heat, or sound is given off
  • Formation of gases, often appearing as bubbles
  • Formation of precipitate (insoluble particles)
  • The decomposition of organic matter (for example, rotting food)