1. Physical and Chemical Changes
Intro to Chemistry

2. Physical Properties
Physical Property: Any characteristic of a material that can be observed or measured without changing the composition (make up) of the substances in the material.
Seven examples of Physical Properties
Viscosity Melting Point
Conductivity Boiling Point
Malleability Density
Hardness

3. Physical Properties
Viscosity: The tendency of a liquid to keep from flowing (syrup has MORE viscosity than water).
Conductivity: A material’s ability to allow heat to flow.
Malleability: The ability of a solid to be hammered without shattering.

4. Physical Properties
Hardness: Compare hardness of objects by seeing which one would scratch the other.
Melting Point: The temp. at which a substance changes from solid to liquid.
Boiling Point: The temp. at which a substance changes from liquid to gas.
Density: can be used to test the purity of a substance.

5. Physical Changes
Physical Change: Occurs when some of the properties of a material change, but the composition of the substance stays the same.
Any change in the form or appearance of matter.
A physical change DOES NOT change the substances chemical makeup.
A physical change DOES NOT produce a new substance.

6. Physical Changes There are TWO types of physical changes.
Reversible Change: A change that can be changed back to its original form.
Irreversible Change: A change that CANNOT be changed back to its original form.

7. Examples of Physical Changes
Reversible Hair being put into a pony tail
Iron removing wrinkles

8. Examples of Physical Changes
Reversible Crumpling Paper Solid to Liquid to Solid – ANY Phase Change

9. Examples of Physical Changes
Reversible Crushing a Can Folded Shirt

10. Examples of Physical Changes
Irreversible Cutting a Piece of Paper Peeled Orange Sliced Tomato Hair Cut

11. Chemical Change
Chemical Change: When one substance reacts and forms one or more new substances.
A chemical reaction occurs when atoms are rearranged not taken away or added.
For you to know that a chemical change has happened A NEW SUBSTANCE MUST BE PRODUCED!!!!
Evidence of a chemical change:
Oxidation (rusting) Flammability
Production of Gas (Bubbles) Warming or Cooling
Formation of a Precipitate (Two Liquids form a solid)

12. Physical Changes & Mixtures
** Reminder: A physical change DOES NOT produce a new substance**
Two Main Types of Mixtures
Heterogeneous Mixture
Homogeneous Mixture

13. Physical Changes & Mixtures
Heterogeneous Mixture: A mixture in which substances are NOT evenly mixed.
In a heterogeneous mixture…
You can easily see the different parts of the mixture OR
You can only see the different parts of a mixture with a microscope.

14. Physical Changes & Mixtures
Example – Blood looks evenly mixed; its color and texture are the same throughout. Under a microscope you can see the uneven mixing.

15. Physical Changes & Mixtures
Example – Granite or Fruit Salad. You can easily see the different parts that make up the substance.

16. Physical Changes & Mixtures
Homogeneous Mixture: A mixture in which substances are evenly mixed.
In a homogeneous mixture…
You CANNOT easily see the different parts of the mixture

17. Chemical Reactions Chemical changes either absorb or release heat!
These reactions are called Endothermic and Exothermic Reactions.
When you need to determine if a reaction is endothermic or exothermic, watch how the temperature of the surroundings changes.
Endothermic reaction – chemical reactions that absorb thermal energy (heat). Cools the surroundings.
Exothermic reaction – chemical reaction that releases thermal energy (heat). Heats the surroundings.

18. Endothermic & Exothermic Reactions
Label each example as Endothermic or Exothermic. Melting Ice Cubes Cooking an Egg A Candle Flame Making Ice Cubes Condensation of Water from Water Vapor Evaporation of Water