1. Section 2.2
Physical Properties

2. Physical Properties Viscosity Conductivity Malleability Hardness
Melting Point
Boiling Point
Density

3. Viscosity The tendency of a liquid to keep from flowing
The greater the viscosity, the slower the liquid flows
Ex: honey has a high viscosity
Ex: water has a low viscosity

4. Honey has a high viscosity
Water has a low viscosity

5. More Viscosity
When you heat a liquid, it’s viscosity usually decreases
Ex: cooking oil in a frying pan
Why is the viscosity of a liquid important?
Ex: motor oil can’t be too thick or too thin

7. Conductivity Conductivity: A material’s ability to allow heat to flow
Conductors are materials that have high conductivity
Ex: metals are excellent conductors
Ex: wood is a bad conductor

8. If you wanted your coffee to cool faster, which spoon would you use, a metal spoon or a wooden spoon?
You should use a metal spoon. The metal will absorb some of the heat energy and release it into the atmosphere faster than the wooden spoon.

9. Malleability
Malleability – the ability of a solid to be hammered without shattering
Ex: most metals are malleable
Ex: Ice cubes are NOT malleable

10. Because gold is so malleable, it is often used in sculptures and jewelry

11. Hardness
To compare hardness, you can see which materials scratch others
Ex: stainless steel can scratch copper. Which material is harder?
Stainless steel!
Diamond is the hardest known material

12. Melting and Boiling Points
Melting point – temperature when solid changes to liquid
Boiling point – temperature when a substance boils
What is the melting point of water?
0°C or °F or K
What is the boiling point of water?
100 °C or °F or K

13. Ice melts at the melting point of water
Water boils at 100 ° C but gold won’t boil until 2856° C

14. Density REMEMBER: Density = mass ÷ volume
It is measured in g/mL or g/cm³
Density can be used to determine the purity of a substance
Ex: the AMA (American Motorcycle Association) requires racers to have at least 99.65% pure methanol fuel.

15. How can we apply density?
Silver has a density of 10.5 g/cm³ (at room temperature)
If a coin has a density of 9.9 g/cm³, what can we determine about the coin’s composition?
Either the coin is not silver, or it is not pure silver

16. Using Physical Properties
Physical properties are used to:
1. Identify a material
2. Choose a material for a certain purpose
3. Separate the substance in a mixture

17. Separating Mixtures Using Physical Properties
Filtration – separates particles based on their size
Distillation – separates substances in a solution based on boiling points

18. Filtration

19. Distillation
This can be used to convert salt water to distilled (pure) water

20. Recognizing Physical Changes
Physical Changes- occur when some of the properties of a material change, but the substances remain the same
Examples:
Crumpling a piece of paper
Slicing a tomato

21. Some physical changes can be reversed and others cannot:
Ex: Braiding hair vs. cutting hair
Are both of these physical changes?
YES!!!