TOC:PHYSICAL/CHEMICAL CHANGES

I STARTER:1.What is the formula for density?

10/7/2013

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?

•Water evaporates from the ocean.

Physical or Chemical Change?•The yolk of an egg, which contains sulfur, causes tarnish to form on silver.

Physical or Chemical Change?

•The ice on a lake melts to become water in the lake.

Physical or Chemical Change?

•Charcoal in a fire turns to ash after several hours.

Physical or Chemical Change?

•A pencil is sharpened in a pencil sharpener, leaving behind shavings.

Physical or Chemical Change?

•A battery makes electricity to turn on a flashlight.

Physical or Chemical Change?

•A bicycle rusts when left in the rain.

Physical or Chemical Change?

•A shirt is accidentally torn in the washing machine.

Physical or Chemical Change?

•A log is split in two by an axe.

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!!!

V. Exit

•SHOW ME YOUR WORK !▫I want to see your completed T-Chart and Connection answer.