Chemicall change

Chemical ChangeChemical Change

Observing, Describing, Controlling

Observing, Describing, Controlling

Observing Chemical ChangeObserving Chemical Change

• Matter can be described in two ways:– Chemical properties– Physical properties

• Matter can be described in two ways:– Chemical properties– Physical properties


• 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.

• 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.


• 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.

• 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.


• Like the properties of matter, the changes it undergoes can be:– Physical Changes

OR– Chemical Changes

• Like the properties of matter, the changes it undergoes can be:– Physical Changes

OR– Chemical Changes


• 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.

• 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.


• 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!!

• 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!!


• 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.

• 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.


• REMEMBER: in order for a chemical reaction to have occurred- bonds must be broken and new bonds must be made!!!

• REMEMBER: in order for a chemical reaction to have occurred- bonds must be broken and new bonds must be made!!!


• EVIDENCE that a CHEMICAL REACTION has occurred: – Change in properties– Change in energy

• EVIDENCE that a CHEMICAL REACTION has occurred: – Change in properties– Change in energy


• 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.

• 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.


• Change in Energy: During chemical changes, energy is either absorbed or released. – Endothermic reactions (heat enters)– Exothermic reactions (heat exits)

• (remember those words…??)

• Change in Energy: During chemical changes, energy is either absorbed or released. – Endothermic reactions (heat enters)– Exothermic reactions (heat exits)

• (remember those words…??)

Describing Chemical ChangesDescribing 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.

• 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.

Describing Chemical ChangesDescribing Chemical Changes

• Generic formula looks like:

Reactant + Reactant ---> Product + Product

• Generic formula looks like:

Reactant + Reactant ---> Product + Product

Conservation of Mass (matter)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.

• During Chemical reactions, atoms cannot be created OR destroyed.

• The total mass of the reactants must equal the total mass of the products.

Conservation of Mass (matter) 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.

• 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.

Open and Closed SystemOpen 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

• 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

Open and Closed SystemOpen 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.

• Open System: Matter can enter from or exit into the surroundings during a reaction.

• Closed System: Matter cannot enter or leave during the reaction.

Chemicall change

Education

Transcript of Chemicall change