Chemical

1
Chemical Changes
2
Essential Questions

• What are chemical changes?
• How do I recognize chemical changes?

3
Chemical Changes

• A Chemical Change is a change that results in one
  or more new substances. When a new substance is
  formed, it can never return to its original
  state.

Take a match and light it. Youll notice the red
tip turns black once a flame has been ignited.
Can you ever take a lit match and turn it back to
its original state? NO! This is because a
chemical change has taken
place.
Take an egg and fry it in a skillet. Once the egg
is cooked, can you ever make it a runny egg
again? NO! This means a chemical change
has taken place.
4
Recognizing a Chemical Change
5
Car For Sale?
We all know that this car has several problems.
Look at the color- it used to be yellow from
what we can tell. Now it is a rusty brown.
What caused this?

• Iron in the metal reacts with
• oxygen in the presence
• of water to form rust.
• Rust is a
• CHEMICAL
• REACTION

6
Is it a Chemical Change?

• A Rotten Egg

A Rusty Nail
YES!
YES!
It changed color- it was silver and hard, now
its brittle and a reddish brown
It has a terrible odor! Remember, anything that
gives off an odor is a chemical change.
7
Is it a Chemical Change?

• Burnt toast

Fireworks
YES!
YES!
It not only changed color from its original
state, but it also gives off smoke after being
lit.
It has a terrible odor and it changed colors. A
burnt piece of toast can never be turned back
into the soft piece it once was.
8
Fire, Fire!!!
Believe it or not, every time wood burns, a
chemical change takes place. Not only is there a
color change, but smoke is released into the air.
Wood that is burnt can never be restored into its
original state. This is why were always left
with ash.
9
Lets Bake some bread!
What happened?
Baking caused a chemical change. You can never
take a baked loaf of bread and turn it back into
dough.
10
Lets Review

• Which always happens during a chemical change?
• A. Matter disappears
• B. A smell is produced
• C. A gas is formed
• D. A new substance is formed

D.
11
Lets Review
Substance Reaction
Vinegar (acetic acid) Penny turned green
Water Penny remains the same
Lemon Juice (citric acid) Penny turned green
Look at the table. What conclusion can you draw
about how substances affect pennies?
Acid changes the color of metal, therefore a
chemical change has taken place.
12
Compare/Contrast

• Suppose you bake a loaf of bread. Suppose you
  draw with marker on paper.
• How are the changes in color that occur different
  from one another?