4. What is “Change”?
It is the act of altering a substance.
An event, NOT a trait.
Before condition After condition.
Can be PHYSICAL or CHEMICAL.
5. All Changes of Matter Involve Energy
being Tranfered and Transformed
Energy always moves between the system
and the surroundings during changes of
matter.
System = the chemicals of interest
Surroundings = everything else (including
the beaker and thermometer)
Energy cannot be created or destroyed, it can
only be transferred from place to place and
transformed from type to type (Law of
Conservation of Energy).
6. Physical Change
Does not alter the chemical composition or
identity of the substance, only the form.
Melting ice (change in state or phase)
Freezing Kool-aid
Tearing paper
Boiling water (change in state or phase)
Stretching silly putty
Making a mixture (ex. Sugar water)
Unmixing a mixture (ex. sorting)
7. States of Matter
The 3 main states of matter: solid, liquid, gas.
Changes in state are physical changes (no
change in composition).
Temperature is caused by the vibrational
(kinetic) energy of atoms or molecules.
As temperature increases, 1) solids turn to
liquids, and 2) liquids turn to gases.
14. Chemical Changes
Does alter the chemical composition or
identity of a substance and makes new
substances.
Burning paper
Digesting food
Rotting
Iron reacting with oxygen gas
A chemical change is also called a chemical
reaction.
15. Exothermic change - heat moves out
the the system into the surroundings.
The surroundings get hotter.
System
Surroundings
System
System
System
16. Endothermic change – Heat moves into
the system from the surroundings, so
the surroundings gets colder!
System
Surroundings
System
Surroundings
System
System
Surroundings
Surroundings
Surroundings
