Unit 2: Properties of Matter
Physical properties: can be observed or measured without changing the composition of matter. Physical properties are used to observe and describe matter. Physical properties include:
* appearance
* texture
* color
* odor
* melting point
* boiling point
* density
* solubility
* polarity and many others.
Ways to separate mixtures (examples):
A solvent is the component of a solution that is present in the greatest amount. It is the substance in which the solute is dissolved. Examples: The solvent for seawater is water.
In chemistry, a solution is a special type of homogeneous mixture composed of two or more substances. ... In such a mixture, a solute is a substance dissolved in another substance, known as a solvent.
For many solids dissolved in liquid water, the solubility increases with temperature. The increase in kinetic energy that comes with higher temperatures allows the solvent molecules to more effectively break apart the solute molecules that are held together by intermolecular attractions.
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The periodic table of elements arranges all of the known chemical elements in an informative array. Elements are arranged from left to right and top to bottom in order of increasing atomic number. The order generally coincides with increasing atomic mass. The rows are called periods.
The vertical columns on the periodic table are called groups or families because of their similar chemical behavior. All the members of a family (groups) of elements have the same number of valence electrons and similar chemical properties.
Hydrogen: This element does not match the properties of any other group so it stands alone. It is placed above group 1 but it is NOT part of that group.
* Very reactive
* Colorless
* Odorless gas at room temperature
Group 1: Alkali Metals: These metals are extremely reactive and are never found in nature in their pure form.
* They are silver colored and shiny
* Their density is extremely low so that they are soft enough to be cut with a
knife.
Group 2: Alkaline-Earth Metals:
* Slightly less reactive than alkali metals
* They are silver colored
* Denser than alkali metals
Groups 3-12: Transition Metals: These metals have a moderate range of reactivity and a wide range of properties.
* Shiny and good conductors of heat and electricity
* They also have higher densities and melting points than groups 1 & 2
Lanthanides and Actinides: These are also transition metals that were taken out and placed at the bottom of the table so that table wouldn't be so long.
* Lanthanides are shiny and reactive.
* The actinides are all radioactive and are therefore unstable.
* Elements 95 through 103 do not exist in nature but have been
manufactured in the lab (man-made)
Stair Step Line: Metalloids: Located between the metals and non-metals. The elements directly to the right of this line are metalloids or semiconductors. These metalloids can be considered BOTH metals AND nonmetals depending on current characteristics such as temperature.
Group 13: Boron Group: Contains 1 metalloid and 4 metals; reactive; Aluminum is in this group. It is also the most abundant metal in the earth's crust.
Group 14: Carbon Group: Contains 1 nonmetal, 2 metalloids, and 2 metals; varied reactivity
Group 15: Nitrogen Group: Contains 2 nonmetals, 2 metalloids, and 1 metal; varied reactivity
Group 16: Oxygen Group: Contains 3 nonmetals, 1 metalloid, and 1 metal
Group 17: Halogens: All nonmetals, very reactive; poor conductors of heat and electricity
Group 18: Noble Gases: Unreactive nonmetals; all are colorless, orderless, gases at room temperature; all found in earth's atmosphere in small amounts.
Valence Electrons:
How do you determine the number of valence electrons?
* The ones place in the group number
Why are they important?
* The valence electrons tells you how reactive that atom is and if it can bond.