CHEMICAL REACTIONS

8.5E – Investigate how evidence of a chemical reaction indicate that

a new substance with different properties has formed

CHEMICAL REACTIONS:

Elements can combine to form new substances

Substances can be broken down into simpler substances

Atoms are re-arranged NOT created or destroyed

CHEMICAL REACTIONS:Formulas and equations express what happens

What is written is a recombination of those atoms

Ex. O2 + 2H2O 2H2O

This “rearrangement” shows that new substances with new properties has been formed

Remember: Law of Conservation

Mass of Reactants = Mass of Products

CHEMICAL CHANGES

A change that produces new substances

Properties of the substances change

Signs (Evidence) of a Chemical Change

Gas is formed/released

Change in odor

Change in temperature

A precipitate forms

Light is produced (flame, bioluminescence, glow sticks, explosions)

Change in color (unexpected)

Sound

Common Misconception Alert!

Temperature change due to adding or removing heat does not represent a chemical change.

For example, melting or freezing is a change of state which is a chemical change.

Specific examples that a chemical change has occurred:

GAS- baking soda and vinegar

COLOR CHANGE- rust

HEAT- fireworks (combustion)

SOLID- lead nitrate + potassium iodide = lead iodide (a precipitate)

Gas is Formed

Elephant’s Toothpaste

Gas Production

Flammable Water

Water = H2O. The batteries split the

H2 and the O. H2 = hydrogen.

Change in Color

Steve Spangler – Color Change

Change in Odor

Rotten Egg Lab

A Precipitate is Formed

Golden Rain

Golden Rain Part 2

Light is Produced

Surprize Fire

Change in Temperature

X on Fire!

Thermite Reaction

Several Examples in One

Multiple Reactions

HW:

Read through the “Chemical Reactions” packet.

On the last page is a table to complete. Use the reading to help you fill in this table.

Due next class

Now let’s observe a chemical reaction!

This is the student version of notes – what reaction we are doing is a surprise – you will just have to come class !