1. Physical & Chemical changes of Matter
Grade 2

2. Content Topics Physical Properties of Matter
Chemical Properties of Matter
Chemical and Physical Changes

3. Macroscopic (Physical) Properties
How compact the material is
Density
What it looks like
Shiny, clear
What it feels like
Smooth, rough
What it does
Conduct electricity
Gets wet

4. Phase
The state (solid, liquid, gas) of the material unless it is heated or cooled.
A phase change is a physical change.
Solid Liquid Gas

5. What is a physical change?
A physical change alters the shape or size.
Physical changes do not change the type of material.
When water is frozen into an ice cube it is still H2O

6. Physical Changes
Ice, water, and steam are all H2O A crumpled piece of foil is still aluminum When we cut a piece of paper in half, we change the length but not the type of material we have. (length is an assessment boundary)

7. Microscopic (Chemical) Properties
The make-up the material (atoms)
Hydrogen + Hydrogen + Oxygen  Water
Structure of the molecule.
Two molecules that contain the same atoms, but have different structures, will have different physical properties.

8. Both are a fuel. One burns faster than the other.

9. What is a chemical change?
A chemical change is a change in the atoms that are present, the make-up of the material.
Chemical changes make a new type of material.
Na + Cl  table salt

10. Chemical Change Indicators
Color change when 2 chemical interact
Production of a gas when 2 materials are mixed
Temperature Change when 2 materials are mixed
Light combustion (flames)
Sound explosions

11. Chemical or Physical? How do we know?
Color wonder paper Chemical – changes color when marker and paper touch
Melted chocolate Physical – this is a phase change caused by heating, nothing was mixed
Food spoils Chemical – a new material forms, there is a color change, there may be production of a gas as well

12. Chemical or Physical? How do we know?
Milk is added to coffee
Physical – the water and milk molecules do not combine to form a new material. While there is a color change, it is simply the combination of the two colors. If the black material plus the white material were mixed and then turned purple, for example, then that would be an indication of a chemical change.

13. How do we know the type of change?
Changes in matter may occur when materials are mixed, heated, or cooled.
Some of these changes do not change the type of matter. (phase change)
Some of these changes do change the type of material. (re-arrange or change atoms in the chemical bonds)

14. Reversible process (unmixing)
Mixing does not always result in a new substance.
Each substance may keep its chemical identity.
Mixtures can be separated which reverses the mixing.
Reversible process (unmixing)

15. How can we separate a mixture?
Separating a mixture isolates the individual types of materials from each other.
Filtration Distillation Osmosis

16. Filtration
Image Credit: wikipedia

17. Distillation
Cooling Device
Pure Water
Heat
Open Source Images

18. Osmosis
Mixture is separated using a membrane. Water passes through but solids do not.
Open Source Image

19. Heating Heating may cause a phase change.
Cooling will make the material look the same as it did before it was heated when there is a phase change.
Ice, Water, Steam
Melted Chocolate
Phase change is a physical change

20. Heating & New Type of Material
Heating may break existing chemical bonds and allow new bonds, new types of materials to form.
Cooling will not make the material look the same as it did before it was heated if there is a chemical change.
Cooking and baking
Cooking is a chemical change

21. Cooling Cooling may cause a phase change.
Cooling something that has experienced a chemical change, will not reverse the process. Cooling will simply cause the new type of material to cool down.
Cooked Egg

22. What does irreversible mean?
If mixed materials cannot be unmixed, then the process was irreversible.
If changing the temperature does not give back the original material(s), then the process is irreversible.
Cookies

23. Reversible Chemical Changes
Some reversible processes are actually chemical processes.
Rechargeable Batteries & Charging a Phone
Open Source Images

24. Reversible Process
Adding energy breaks apart the chemical bonds that formed. The components can then re-combine and be broken apart again.
The reversible process of recharging batteries is a chemical change.

25. Practice
When you strike a match, are you adding energy? Yes, you are adding energy. Striking the match creates friction which results in heating.
Is there a change in the type of material that the match head is? Yes, the match head changes color and texture; there is new material.
Is this change a physical or chemical change? Why? Chemical – new substance was formed (soot)

26. Changes in Matter
The key to separating physical and chemical changes is to determine whether a new type of material is present after mixing, heating, or cooling.
Reversible and irreversible changes apply to both physical and chemical transformations.