Changing matter
Transcript of Changing matter
Changing Matter• Matter can be changed two ways:
–Physically • Physical reaction
• Physical change
–Chemically• Chemical reaction
• Chemical change
Physical Changes
• Do NOT CHANGE THE TYPE OF MATTER
– Nothing new or different is formed– Could be a change in:
• Mass
• Volume
• Hardness
• Color
• Density
How to Recognize a Physical Change
• Change in. . .– Size– Shape– State
Examples of Physical Changes
• Boiling • Freezing• Dissolving • Breaking • Making a mixture
– 2 or more types of matter (substances) mixed together
• Not in specific amounts• Can be separated physically
Chemical Properties
• Describes how a substance reacts
• Examples:– What happens when
it’s burned?– What happens when
it’s mixed with vinegar?
Chemical Changes
• Evidence of a chemical reaction– Formation of gas (bubbles form)– Formation of precipitate (new substance)– Change in color– Change in energy (heat and light)
• Endothermic– Absorbs heat energy (gets cold)
• Exothermic– Releases heat energy (gets hot)
Examples of a Chemical Change
• Burning anything• Rusting• Tarnishing• Baking a cake• Frying eggs
Chemical Changes
• Atoms are re-arranged, NOT created or destroyed– Law of Conservation of Matter– Law of Conservation of Mass
Chemical Changes
• Matter is conserved type of atoms does not change– Nothing is created or destroyed
• Mass is conserved amount of atoms cannot change– Nothing is created or destroyed
Chemical Changes
• To show conservation of mass Balance equations– Make sure there are the same number of
each type of atom in the products and in the reactants
Balancing Equations
The equation for the burning of methane gas in oxygen is:
CH4 + 2 O2 → CO2 + 2 H2O
Subscript
Shows # of atoms
Coefficient
Shows # of molecules
Balanced Equation
CH4 + 2 O2 → CO2 + 2 H2O
Reactants Products (Original Substances) (New Substances Formed)
Types of Chemical Reactions
• Synthesis Reaction2 or more simple substances combine to form a more complex substance.
A+B AB
• Decomposition Reaction
A more complex substance breaks down into its more simple parts
AB A + B
Types of Chemical Reactions
• Replacement Reactions
AB + CD AD + CB