What are examples of extensive physical properties?
How useful are extensive properties at defining what a substance is?
- volume (length* width* height)
- Not very useful because they change depending on the amount of substance you have
What is an intensive physical property?
- as the volume increases, the mass increases. They increase in a directly proportional fashion, making the value of density a constant, and, therefore, an intensive physical property.
What are examples of chemical properties?
- burning (oxidative/ reduction reactions) combination of a substance with oxygen
Why do we use physical and chemical properties?
- To try to determine the characteristics of a substance. The easiest to measure are the physical properties because you can take a sample and measure the other physical properties.
- The chemical changes are not as easy to identify because, usually, what you begin with is not what you end up with. It changes.
Explain the first group of the periodic table.
- Alkali metals (most metallic metals)
- - In terms of reactivity, going down the family, the reactivity increases
- - periodic trend= if thrown into water, they react with water, getting more reactive as you go down.
- - They turn the solution basic.
- - You will not find the solid metals in nature because they would have already reacted with moisture in the air.
Is Hydrogen a part of the Alkali metals? Why or why not?
No because it is not an alkali metal. In certain situations, it acts like them because it forms a positive charge. But, it also forms a negative charge.
Explain the 2nd group of the Periodic Table.
- Alkaline Earth Metals
- - react a bit, but not as much, with water
- - Some are found in earth, but, for the most part, they would have reacted already
What is the 7th column?
Explain the 8th column (17th family) of the periodic table.
- Noble gases
- - not very reactive (inert)
- - some can undergo chemical reactions, but they are very unreactive
- - will not be included in periodic trends due to unreactivity
What is the periodic table divided into?
- Metals (before zig-zag)
- Nonmetals (after zig-zag)
- Semi-metals (zig-zag)
Explain metal properties.
- - ductile and malleable
- - luster (ability to reflect light- shiny in nature)
- - conduct heat/ electricity
- - solids at room temp except mercury and gallium
Explain non-metal properties.
- hydrogen is included in this
- - in elemental form, some are diatomic
- ---> instead of single atom present, there are two atoms joined together
- -------> Hydrogen, Nitrogen, Fluorine, Oxygen, Iodine, Chlorine, Bromine
- - No noble gases exist diatomically due to unreactivity, therefore, they are not included
Explain semi-metal properties.
- some are semi-conductors
- - under certain conditions, they conduct electricity
What is used to measure:
amount of a substance
Mass vs. Weight
- Mass: amount of matter in an object
- Weight: measures the force with which gravity pulls on an object
- - if on moon, mass won't change, weight will.
Temperature vs. Heat
Explain the two.
- Temperature: avg. kinetic energy associated with the particles
- - kinetic energy also has a mass factor
- ---> the heavier something is, the less kinetic energy it will have at a given temperature
- Heat: amount of thermal energy transferred from one object to another (hotter--> cooler)
What are the three ways to measure temperature?
- Kelvin: waater freezes at absolute zero 273 K (where no particles moves) and boils at 373 K
- Fahrenheit: freezes at 32o and boils at 212o
- Celsius: freezes at 0o and boils at 100o
What is the Kelvin scale offset by with Celcius?
How do you convert Kelvin to Celsius?
How do you convert Fahrenheit to Celsius?
(5oC/9oC) * (oF -32oF)
How do you convert Celsius to Fahrenheit?
(9oF/5oC) * oC + 32oF