1. Unit 3: Chemical Reactions
Add the new notes to your table of contents, and then turn to the next clean page and set up your title and date

2. Tape the two slides into your INB flat down, directly under your title - they do not need to flip up

3. Identifying A Substance (Recap)
As you learned in Unit 2:
Substances react chemically in characteristic ways, which can be used to identify a substance
For example – Baking Soda always reacts with vinegar by fizzing/bubbling
Properties that can be used to identify a substance are unique or characteristic
Examples: density, chemical reactions, chemical formula
During a chemical change, the atoms that make up the original substance are regrouped into different molecules
This is what forms the new substances
The change in formation of atoms means the new substances have new physical and chemical properties

4. Notice in these two examples that many properties have changed, but as we noted in Unit 2, the only ones that prove a chemical change has occurred are the unique characteristic properties of:
Chemical formula
Melting point/Boiling point
Density

5. Conservation of Mass
Also notice that before and after the chemical change occurs, we have the same number of atoms for each element

7. Conservation of Mass
Also notice that before and after the chemical change occurs, we have the same number of atoms for each element
Before the change we have 2 Copper atoms and 2 Oxygen atoms, after we still have 2 Copper atoms and 2 Oxygen atoms, although they have been regrouped/rearranged
Before the change we have 2 Hydrogen atoms and 1 Oxygen atom, after we still have 2 Hydrogen atoms and 1 Oxygen atom, although they have been regrouped/rearranged

9. Add Conservation of Mass to your Index
The Law of Conservation of Mass states that matter cannot be created or destroyed – the mass before and after a chemical reaction has occurred will always be the same
The total number of each type of atom in a chemical process is conserved, and thus the mass does not change.
Matter is conserved because atoms are conserved in physical and chemical processes.
Add Conservation of Mass to your Index

11. Is Mass Conserved here?

13. Is Mass Conserved here?

14. Endothermic and Exothermic Reactions
Some chemical reactions release energy, while others store energy.
A chemical reaction involves the breaking of bonds in the reactants and the forming of bonds in the products.
It takes energy to break bonds.
Energy is released when bonds are formed.

17. Endothermic Reactions
Exothermic Reactions
two substances react and the temperature of the mixture decreases
In an endothermic reaction, it takes more energy to break the bonds of the reactants than is released when the bonds of the products are formed
two substances react and the temperature of the mixture increases
In an exothermic reaction, more energy is released when the bonds of the products are formed than it takes to break the bonds of the reactants

18. Endothermic Reactions
Exothermic Reactions
Add
Endothermic Reaction
and
Exothermic Reaction to your Index