Chemical/Physical Change
Ice melting is what type of change?
Physical change
HOW DO WE REPRESENT A CHEMICAL REACTION?
Chemical Equation
CHEMICAL POTENTIAL ENERGY IS STORED IN THE ____________ OF COMPOUNDS AND MOLECULES.
Bonds
What law says matter cannot be created or destroyed?
Law of Conservation of Mass
Balance: H₂ + O₂ → H₂O
2H₂ + O₂ → 2H₂O
Burning wood is what type of change?
Chemical change
WHAT IS A CHEMICAL EQUATION?
a shorthand method that uses symbols to tell what elements are in a compound and their ratios.
Determine which of the following Examples are Endothermic or Exothermic Reaction
1. Hand warmers
2. Two chemicals are mixed and get cold
1. Exothermic
2. Endothermic
What must stay the same in a chemical reaction?
Number of atoms
Balance: Na + Cl₂ → NaCl
2Na + Cl₂ → 2NaCl
HOW DO WE KNOW A CHEMICAL REACTION HAS TAKEN PLACE?
We observe indicators of a chemical change.
Subscript is ...
Written after a symbol to tell how many atoms of that element are in a unit of the compound.
Which type of reaction releases heat? and Which type absorbs heat?
Exothermic (releases heat): warmer surrounding
Endothermic (absorbs heat): colder surrounding
Energy cannot be created or destroyed—this is called what?
Law of Conservation of Energy
Balance: Fe + O₂ → Fe₂O₃
4Fe + 3O₂ → 2Fe₂O₃
Define Chemical Change
New substances are produced by the making and/or breaking of bonds.
Coefficient is
The number of units of each substance taking part in a reaction.
IN A CHEMICAL REACTION,
ENERGY CAN TAKE MANY FORMS, What are those forms? (hint 4)
- Heat
- Light
- Sound
- Electricity
Why must equations be balanced?
To follow the law of conservation of mass
What can you change to balance an equation?
Coefficients
WHAT ARE THE INDICATORS OF A CHEMICAL CHANGE? list at least 5 (100 points for every indicator)
A. Formation of a gas. (bubbles)
B. Formation of precipitate
C. Production of light
D. Production of sound
E. A temperature change
F. Production of an Odor
G. An unexpected color change
State of Matter: are symbols tell the state of matter of the substance - what are these symbols (hint: there are 4)
solid (s),
liquid (l),
gas (g), or
aqueous (aq) [dissolved in water]
What is the difference between exergonic and endergonic?
True or False: Atoms can disappear in a reaction
False
Balance: C₃H₈ + O₂ → CO₂ + H₂O
C₃H₈ + 5O₂ → 3CO₂ + 4H₂O