Chapter 4 Elements, Compounds & Mixtures Section II
Chapter 4
Elements, Compounds & Mixtures Section II
Section 2 - Compounds
II. COMPOUNDS (p.86-89)- a compound is a pure substance composed of elements that are chemically combined. In order to combine chemically they must react or undergo a chemical change. What are the clues to a reaction?
An example of a reaction or chemical changeFireWorks Video 5/18/02 800kb
FireWorks_320x240.avilidmanmusic.com/sled/
SALT Sodium (Na) combines with Chlorine (Cl)
Section 2 - Compounds
A. Elements combine in a definite ratio to form a compound-
A ratio is a comparison of two numbers. It usually looks like a fraction or a time
1/6 or 1:6 or 1 to 6
http://www.windows.ucar.edu/earth/geology/images/water_molecules_sm.gif
Note to martin- add atom ratio and a second example c6h12o6
Ex.) The mass of hydrogen to the mass of oxygen in water is always 1 gram of hydrogen for every 8 grams of oxygen. If the ratio is different, it is not water.What does an atom of oxygen weigh?
16 amuWhat does an atom of hydrogen weigh ?
1 amuHow many atoms of hydrogen in water?2What is the mass ratio ?2:16 which reduces to 1:6
Section 2 - CompoundsB. Every compound has a unique set of properties-
1. Like elements, compounds have their own sets of
chemical properties like boiling point, density and
color.
2. A compound has different properties than the elements that
form it. (Ex.Sodium chloride)www.powerlabs.org/ chemlabs/sodium.htm
http://www.vanderkrogt.net/elements/images/sodium.jpghttp://www.webelements.com/webelements/elements/media/element-pics/Cl.jpg
resourcescommittee.house.gov/.../ photogallery/
Click pic for video
Na
NaCl
Section 2 - Compounds
C. Compounds can be broken down into element or simpler compounds through chemical changes.
http://www.bytocom.com/Gallery/images/electrolysis.gif
1. These chemical changes can be brought about by running electricity though the substance (water and melted sodium chloride) heating the substance (Mercury (II) oxide) or sometimes even exposure to sunlight (hydrogen peroxide).
Section 2 - Compounds
2. Compounds cannot be broken down by
physical changes.
a. Physical changes include filtration, and
grinding the substance into a powder. (Boiling and melting are also physical changes)
Compound review video
Section 2 – CompoundsD. Compounds in your world. 1. Compounds in nature a. Nitrogen is a key element needed to make proteins. Those proteins can only be made by nitrogen compounds. Bacteria in the soil make those nitrogen compounds. http://www.beefretail.org/uDocs/1133Shoulder%20Steak.JPG
anka.livstek.lth.se:2080/ rootnodules.htm
Section 2 - Compounds
b. Another important compound is carbon dioxide.
Carbon dioxide is exhaled by animals and
people and used by plants. Plants then use the
carbon dioxide to make other compounds like
sugar.
Section 2 - Compounds
E. Compounds in industry a. Nitrogen is combined with the element hydrogen to form a compound called ammonia that is manufactured for fertilizers. There are many other compounds manufactured in
industry.
http://www.uyseg.org/greener_industry/pages/ammonia/images/ammonia.gif
Section 2 - Compounds
b. The compounds found in nature are often not the materials needed for industry. Often the compounds need to be broken down to provide elements used for raw materials. For example, aluminum that is used in cans and airplanes is not
found alone in nature. Breaking down the compound aluminum oxide produces it.
http://mineral.galleries.com/minerals/oxides/spinel/spinel.jpg http://www.leeric.lsu.edu/energy/rrr/aluminum2.gif
Fun little clip on this topic