Chemical Change
Observing, Describing,
Controlling
Observing Chemical Change
• Matter can be described in two
ways:
– Chemical properties
– Physical properties
Observing Chemical Change
• Chemical Properties: The
characteristics of a substance that
describes it’s ability to change ...
Observing Chemical Change
• Physical Properties: a characteristic
of a substance that can be
observed without changing the...
Observing Chemical Change
• Like the properties of matter, the
changes it undergoes can be:
– Physical Changes
OR
– Chemic...
Observing Chemical Change
• Physical Changes: Any change that
alters the form, shape, or
appearance of a substance but
doe...
Observing Chemical Change
• Chemical Changes: a change that
a substance undergoes where a
totally new substance is the res...
Observing Chemical Change
• During a chemical change you
have:
– Reactants: the substance that is being
changed.
– Product...
Observing Chemical Change
• REMEMBER: in order for a chemical
reaction to have occurred- bonds
must be broken and new bond...
Observing Chemical Change
• EVIDENCE that a CHEMICAL
REACTION has occurred:
– Change in properties
– Change in energy
Observing Chemical Change
• Change in properties: color change,
a solid forms (precipitate), formation
of gas, and texture...
Observing Chemical Change
• Change in Energy: During chemical
changes, energy is either absorbed
or released.
– Endothermi...
Describing Chemical Changes
• Chemical equations are used to
show/explain a chemical reaction.
– This shows the reactants ...
Describing Chemical Changes
• Generic formula looks like:
Reactant + Reactant ---> Product + Product
Conservation of Mass (matter)
• During Chemical reactions, atoms
cannot be created OR destroyed.
• The total mass of the r...
Conservation of Mass (matter)
• In a chemical reaction, the number
of atoms stays the same- they are
just rearranged. Ther...
Open and Closed System
• Sometimes it’s hard to understand
where the matter comes from in a
reaction.
• Matter can either ...
Open and Closed System
• Open System: Matter can enter from
or exit into the surroundings during a
reaction.
• Closed Syst...
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Chemicall change

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Chemicall change

  1. 1. Chemical Change Observing, Describing, Controlling
  2. 2. Observing Chemical Change • Matter can be described in two ways: – Chemical properties – Physical properties
  3. 3. Observing Chemical Change • Chemical Properties: The characteristics of a substance that describes it’s ability to change into a different substance. – EXAMPLE: In our magnesium lab, we lit the magnesium on fire, watched it burn as it reacted with the oxygen in the air. This was its chemical property: flammability.
  4. 4. Observing Chemical Change • Physical Properties: a characteristic of a substance that can be observed without changing the substance into something new. – EXAMPLE: Frozen water (ice) melts at 0 degrees Celsius. The tops of the tables in this room are black and 4.5ft long.
  5. 5. Observing Chemical Change • Like the properties of matter, the changes it undergoes can be: – Physical Changes OR – Chemical Changes
  6. 6. Observing Chemical Change • Physical Changes: Any change that alters the form, shape, or appearance of a substance but does not change it into a new substance. – EXAMPLE: If I were to toss fresh berries into a blender and make a fruit smoothie- it would still be fruit, just mashed into smaller pieces.
  7. 7. Observing Chemical Change • Chemical Changes: a change that a substance undergoes where a totally new substance is the result. – EXAMPLE: In the magnesium lab, we burned magnesium and after it’s chemical change the result was magnesium oxide. It was no longer metal!!
  8. 8. Observing Chemical Change • During a chemical change you have: – Reactants: the substance that is being changed. – Products: the new substance formed as a result of the chemical reaction.
  9. 9. Observing Chemical Change • REMEMBER: in order for a chemical reaction to have occurred- bonds must be broken and new bonds must be made!!!
  10. 10. Observing Chemical Change • EVIDENCE that a CHEMICAL REACTION has occurred: – Change in properties – Change in energy
  11. 11. Observing Chemical Change • Change in properties: color change, a solid forms (precipitate), formation of gas, and texture change. • CAUTION!! Sometimes physical changes make it SEEM like a chemical change has occurred. Really THINK about the changes.
  12. 12. Observing Chemical Change • Change in Energy: During chemical changes, energy is either absorbed or released. – Endothermic reactions (heat enters) – Exothermic reactions (heat exits) • (remember those words…??)
  13. 13. Describing Chemical Changes • Chemical equations are used to show/explain a chemical reaction. – This shows the reactants and products of a reaction – They show the substances you start with, on the left and the new substances on the right separated by an arrow.
  14. 14. Describing Chemical Changes • Generic formula looks like: Reactant + Reactant ---> Product + Product
  15. 15. Conservation of Mass (matter) • During Chemical reactions, atoms cannot be created OR destroyed. • The total mass of the reactants must equal the total mass of the products.
  16. 16. Conservation of Mass (matter) • In a chemical reaction, the number of atoms stays the same- they are just rearranged. Therefore, the number of atoms in the reactants are the same as the number of atoms in the products.
  17. 17. Open and Closed System • Sometimes it’s hard to understand where the matter comes from in a reaction. • Matter can either come from an… – Open System or a… – Closed System
  18. 18. Open and Closed System • Open System: Matter can enter from or exit into the surroundings during a reaction. • Closed System: Matter cannot enter or leave during the reaction.

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