1. Physical Properties (Section 2.2)

2. Physical Properties
Is any characteristic of a material that can be observed or measured without changing the composition of the substances in the material
Viscosity, conductivity, malleability, hardness, melting point, boiling point, and density are examples of physical properties

3. Viscosity
Viscosity is the tendency of a liquid to keep from flowing (its resistance to flowing)
The greater the viscosity, the slower the liquid moves
Thick liquids like corn syrup and honey have a high viscosity
Thin liquids like vinegar and water have a low viscosity
The viscosity of a liquid usually decreases when it is heated

4. Conductivity A material’s ability to allow heat to flow
Materials that have a high conductivity, such as metals, are called good conductors
If a material is a good conductor of heat it is usually also a good conductor of electricity
Wood is not a good conductor of heat

5. Malleability
Is the ability of a solid to be hammered without shattering
Most metals are malleable
Solids that shatter when struck are brittle

6. Hardness
Tip of drill is coated in diamond
One way to compare the hardness of two materials is to see which of the materials can scratch the other
Diamond is the hardest known material

7. Melting & Boiling Points
The temperature at which a substance changes from a solid to a liquid is its melting point
The temperature at which a substance boils is its boiling point (liquid to gas)
Melting and Boiling Points of Some Substances
Substance
Melting point
Boiling point
Hydrogen C C
Nitrogen C C
Ammonia
-77.70C
-33.30C
Octane (found in gasoline)
-56.80C
125.60C
Water
0.00C
100.00C
Acetic Acid (found in vinegar)
16.60C
117.90C
Table Salt
800.70C
14650C
Gold C
28560C

8. Density Is the ratio of the mass of a substance to its volume
Density = Mass
Volume
Can be used to test the purity of a substance
Silver has a density of 10.5 g/cm3 at room temperature but if you have a coin with a density of 9.9 g/cm3 at room temperature it must not be pure

9. Using Properties to Identify Materials
Step 1: decide which properties to test
Step 2: do tests on a sample of the unknown
Step 3: compare the results with the data reported for the known materials
When a car is involved in a hit-and-run accident detectives use paint chips from the scene of the crime to identify the make and model of the vehicle using a database of the different paint mixtures

10. Using Properties to Choose Materials
People don’t consider just one property when choosing a material for a particular application
Example
You wouldn’t want shoelaces made of wood or steel
Shoelaces need to be flexible, durable, and easy to secure

11. Separating Mixtures Some properties can be used to separate mixtures
Filtration
Uses a porous barrier to separate a solid from a liquid
Good for heterogeneous mixtures

12. Distillation
Uses differences in the boiling points of the substances involved
Crystallization
Results in the formation of pure solid particles of a substance from a solution containing the dissolved substance

13. Chromatography
Parts of a mixture are separated based on how fast they travel through a medium

14. Recognizing Physical Changes
A physical change occurs when some of the properties of a material change, but the substances in the material remain the same
Change in the state of matter

15. Physical Changes
Crumpling a piece of paper changes the size and shape of the paper and slicing a tomato changes the size and shape of the tomato but it does not change their composition
Some physical changes can be reversed such as melting ice and then freezing it again
Some cannot be reversed (You can’t put the sliced tomato back together and make it whole)