1. Materials…
What happens when?

2. Explain Why..

4. Degradation …

5. Chemical Reactions What is a chemical reaction?
What are the signs of a chemical reaction?

6. Chemical Reactions What is a chemical reaction?
A reaction that modifies the nature of a substance (how it is made) and, therefore, changes the properties of the substance

7. Chemical Review Signs of Chemical Reaction Gas formation
Release or absorption of energy (light or heat)
Precipitation
Color change

8. Chemical Reactions 2. Types of chemical changes
A) Synthesis vs. Decomposition
B) Photosynthesis vs. Cellular Respiration
C) Oxidation
D) Combustion

9. Chemical Reactions 2. Types of chemical changes
A) Synthesis vs. Decomposition
Synthesis
When 2 or more molecules or elements become one molecule
They Combine together
Decomposition
When 1 molecules is broken down into 2 or more molecules or elements
They break apart

10. Chemical Review 2. Types of chemical changes
A) Synthesis vs. Decomposition
Synthesis
Decomposition

11. What type of reaction are these?
2 H2(g) + O2(g) → 2 H2O(g)
2 CO(g) + O2(g) → 2CO2(g)
2 NH3(g) →3 H2(g) + N2(g)
4 Al(s) + 3 O2(g) → 2 Al2O3(s)
8 FeS→8 Fe + S8
 2 K(s) + Cl2(g) → 2 KCl(s)

12. Chemical Review 2. Types of chemical changes
B) Photosynthesis vs. Cellular Respiration
Cellular Respiration
What we do
Takes in Oxygen
Photosynthesis
Plants (during the day)
Takes in Carbon dioxide

13. Chemical Reactions 2. Types of chemical changes C) Oxidation
Chemical reaction that requires oxygen as a reactant.
E.g. corrosion (a.k.a. rust)

14. Chemical Review 2. Types of chemical changes C) Oxidation
Requires Oxygen
2 Mg + O2 ----> 2 MgO
E.g. corrosion

15. Chemical Review with the Particle model
2. Types of chemical changes
C) Oxidation
Requires Oxygen
2 Mg + O2 ----> 2 MgO
>
E.g. corrosion

16. Chemical Reactions 2. Types of chemical changes D) Combustion
Chemical reaction that requires oxygen (or oxidizing agent) as a reactant and releases energy.

17. Chemical Review 2. Types of chemical changes
D) Combustion
Requires Oxygen as a product
Gives off energy
CH4 + 2O2 = CO2 + 2 H2O + energy

18. Combustion side note: Types of combustion: Slow Rapid Spontaneous
Requires outside energy input
gives off heat and light that is observable
Spontaneous

19. Fuel Oxidation Ignition Agent Temperature
Combustion Triumvirate (Fire Triangle)
Fuel
Oxidation
Agent
Ignition
Temperature

20. What kind of reaction? CH4(g) + 2 O2(g) CO2(g) + 2 H2O(g)+ energy
2 Fe(s) + O2(g)   2 FeO(s)

21. Constraints Constraints are Constraints describe
The different types of stress the material undergoes
Constraints describe
the effect of external forces on a material
E.g. weight of a building
** Dead load: weight of the bridge itself
** Live load: weight added on the bridge

22. Types of constraints Compression:
When a material is subjected to forces that tend to crush it Hi

23. Tension When a material is subjected to forces that tend to stretch it
That was close

24. Torsion When a material is subjected to forces that tend to twist it
Do you mind?

25. Deflection
When a material is subject to forces that tend to bend it

26. Shearing
When a material is subjected to forces that tend to cut it

27. Types of material deformation
Elastic:
When the constraint leads to a temporary change in the shape or dimensions of the material. When the constraint is removed, the material returns to its original form
Plastic:
The constraint leads to a permanent change in the shape or dimensions of the material. Even when the constraint is removed, the material remains deformed
Fracture:
The constraint is so intense that it breaks the material