toc:physical/chemical changes i starter: 1.what is the formula for density? 10/7/2013
TRANSCRIPT
Physical Changes• a change that occurs
changing the of the substance.
• ____ new substances are formed.
withoutidentity
No
Physical Change:
1)Whipping egg whites – air is forced into the fluid, but no new substance is produced!
2)Sugar dissolving in water – sugar molecules are spread
within the water, but the individual sugar molecules are
unchanged
3)Boiling water –water molecules are forced away from each
other when the liquid changes to vapor, but molecules are
still H2O
4)Dicing potatoes – cutting usually separates molecules
without changing them.
Chemical Changes• a change that occurs
that the of a substance to change; something is formed.
• New substances with properties are
formed
causesidentity
new
new
Chemical Change:
1) Iron rusting – Iron oxide forms through the reaction
of iron and oxygen in the presence of water or air
moisture.
2) Gasoline burning – when gasoline is burned in car
engines, water vapor and carbon dioxide
form.
3) Eggs cooking - Fluid protein molecules uncoil and
crosslink to form a network.
4) Bread rising – Yeast changes carbohydrates into
carbon dioxide gas.
5) Milk souring – When bacteria use the lactose sugars
in milk they change the sugar and sour-tasting lactic
acid is produced.
SIGNS OF CHEMICAL CHANGE (How can you tell?)
▫Gas Formation– a gas is formed & released as the reaction is completing (NOT the same as boiling)
▫Solid formation (precipitate) – a solid “rains down” to the bottom of the container, may be suspended in a cloudy solution
▫Temperature Change – It takes energy to break chemical bonds. Energy is released (heat) OR energy is absorbed (cold).
▫Color Change – Not the same as mixing colors.▫Light is given off▫Change in smell (or taste)
Application•Construct a T-Chart•Categorize each following example as a
physical or chemical change
Physical Change Chemical Change
Physical or Chemical Change?•The yolk of an egg, which contains sulfur, causes tarnish to form on silver.
Connection•List 3-5 places or professions where
paying attention to physical and chemical changes might be important?
•Predict what might happen if you didn’t pay attention to the physical/chemical changes in your answer above.
▫USE COMPLETE SENTENCES!!!