A chemical change occurs when the atoms within a substance rearrange into different combinations, resulting in different molecules than the original reactants. During a chemical change, chemical bonds are formed or broken as elements combine or decompose. Examples of chemical changes include sugar caramelizing during cooking as molecules rearrange, and iron rusting as it reacts with oxygen and water in the air.
2. WHAT IS A CHEMICAL CHANGE?
• MATTER CAN GO THROUGH PHYSICAL CHANGES AND CHEMICAL CHANGES. A
PHYSICAL CHANGE OCCURS WHEN A SUBSTANCE CHANGES STATES OF MATTER,
OR ITS SIZE OR SHAPE. DURING A PHYSICAL CHANGE THE SUBSTANCE, ELEMENT,
OR COMPOUND DOES NOT CHANGE. HOWEVER, THE CHANGE MIGHT INVOLVE
CHANGES IN ENERGY. FOR EXAMPLE, ICE MELTING IS A PHYSICAL CHANGE IN
THAT AN INCREASE IN THERMAL ENERGY CHANGES THE STATE OF MATTER OF
WATER. HOWEVER, THE WATER MOLECULES THEMSELVES ARE STILL WATER, I.E.,
TWO HYDROGEN ATOMS ARE STILL BONDED TO ONE OXYGEN ATOM. A
CHEMICAL CHANGE, ON THE OTHER HAND, INVOLVES A CHANGE IN CHEMICAL
BONDS OR MOLECULAR COMPOSITION, I.E., CHEMICAL ELEMENTS EITHER
CREATE BONDS OR BREAK BONDS BETWEEN THEM. AN EXAMPLE IS WHEN IRON
REACTS WITH AIR AND WATER TO CREATE RUST. RUST (HYDROUS IRON OXIDES
AND IRON OXIDE-HYDROXIDE) IS A COMBINATION OF IRON, OXYGEN, AND
3. • A CHEMICAL CHANGE OCCURS AS THE RESULT OF A
CHEMICAL REACTION. DURING A CHEMICAL REACTION,
THE ATOMS WITHIN A SUBSTANCE ARE REARRANGED
INTO DIFFERENT COMBINATIONS. FOR EXAMPLE, SUGAR
UNDERGOES A CHEMICAL CHANGE WHEN IT IS COOKED
TO MAKE CARAMEL. THE HEAT FROM THE COOKING
CONVERTS SUGAR MOLECULES INTO DIFFERENT
MOLECULES THAT GIVE CARAMEL ITS COLOR AND
FLAVOR.
4. TYPES OF CHEMICAL CHANGE
• COMBINATION - HAPPENS WHEN TWO OR MORE SUBSTANCES
COMBINE TOGETHER IN A CHEMICAL REACTION TO FORM
ONE OR MORE DIFFERENT SUBSTANCES. COMBINATION
REACTIONS CAN RESULT IN THE CORROSION OF METALS, LIKE
IRON WITH OXYGEN FROM THE AIR. COMBUSTION
REACTIONS, SUCH AS A BURNING CANDLE, ARE ALSO
EXAMPLES OF THE CHEMICAL CHANGE THROUGH THE
COMBINATION OF WAX AND OXYGEN IN A REACTION THAT
PRODUCES HEAT, LIGHT, AND CARBON DIOXIDE.
5. TYPES OF CHEMICAL CHANGE
• DECOMPOSITION -, THE OPPOSITE OF COMBINATION,
OCCURS WHEN A SINGLE SUBSTANCE BREAKS DOWN
INTO TWO OR MORE DIFFERENT SUBSTANCES. THIS TYPE
OF CHEMICAL CHANGE IS EVIDENT WHEN FRUIT
DECOMPOSES OVER TIME. DECOMPOSITION CAN ALSO
OCCUR WHEN SUBSTANCES ABSORB ENERGY, SUCH AS
THE DECOMPOSITION OF WATER INTO HYDROGEN AND
OXYGEN WITH ELECTRICITY.
6. THE THREE MAIN PARTS OF CHEMICAL
REACTION
• THE THREE MAIN PARTS OF A CHEMICAL REACTION ARE REACTANTS,
ARROW, AND PRODUCTS.
• REACTANTS: DURING A REACTION, THESE COMPOUNDS OR ELEMENTS
COMBINE AND UNDERGO SOME CHEMICAL CHANGES. THESE ARE
PRESENT ON THE LEFT SIDE OF THE REACTION EQUATION. FOR EXAMPLE,
• ARROW: IN OTHER WORDS, THIS INDICATES THE FORMATION OF
PRODUCTS FROM THE REACTANT, AS WELL AS SEPARATING THE
REACTANT AND PRODUCT. IT IS REPRESENTED AS,
• PRODUCTS: PRODUCTS ARE FORMED AS A RESULT OF CHEMICAL
REACTIONS BETWEEN THEIR REACTANTS. THIS IS PRESENT ON THE RIGHT
SIDE OF THE CHEMICAL EQUATION. FOR EXAMPLE,
