Place a charcoal briquette into a plastic sandwich bag and take it to the hammer
ID: 158372 • Letter: P
Question
Place a charcoal briquette into a plastic sandwich bag and take it to the hammering nation in your lab. Lightly hammer the bag enough to break apart the briquette. Return to your table with the bag of charcoal. View the broken piece of charcoal with a hand lent. Describe what kind of grains you see and their texture. Charcoal is made by allowing wood to smolder just enough that an impure mass of carbon remains. In the presence of oxygen, the charcoal briquette will naturally combine with oxygen to make carbon dioxide. Over a period of many years, it will all react with oxygen and chemically weather to carbon dioxide. When you burn charcoal in your grill, yon are simply speeding up the process. However, if plant fragments are buried beneath layers of sediment that keep oxygen away from them, then they can slowly convert to a charcoal like rock (peat, lignite, or coal) and remain so for millions of years. Obtain a piece of coal and compare it to your charcoal. How is it different? Why? Based on your observations in tins activity, write a definition of biochemical sedimentary rock in your own words. Bedrock can remain buried underground for millions to billions of years. However, when it is exposed to water and air at Earth's surface it weathers chemically and physically, for example, acidic water reacts with potassium and plagioclase feldspars ro make clay minerals plus water containing dissolved silica (hydrosilicic acid) and metallic ions (K, Na, Ca). This is one of the main sources of clay found in soil and wont assay into rivers and the ocean. The metals in many minerals oxidize (combine with oxygen) to form metal oxides like limonitc ("rusty" iron) and hematite. Obtain and observe samples of both. What is the color and chemical formula lot hematite? (Refer to Minerals Database. page 95) What is the color and chemical formula for limonite? (Refer to Minerals Database, page 96) As iron oxides form, they act like glue to cement together grains of sediment, like the "sandstone" above. Which iron oxide mineral has cemenred together this sandstone? How can you tell? Powder some limonite in a morrar and pestle, and note its true streak color (yellow-brown). Put on safety goggles. In a frame hood or behind a glass shield, heat some of the powder in the Pyres rest tube over the Bunsen burner. Be sure to point the test tube at an angle, away from people. After about a minute of heating, pour the hot limonite powder onto the toil on the table. What happened to the yellow-brown limonite? Why? The rapid chemical change that you observed above can occur quickly only at temperatures like those above the Bunsen burner. However, some modern desert soils do contain hematite and appeal red. How can that be?Explanation / Answer
1. The colour of hematite is Black, gray to silver gray, brown to reddish brown, red. Some specimens are iridescent, and other are multicolored or banded gray and dark red.
Chemical formula of hematite is Fe2O3.
2. The colour of limonite is Yellow, brown, reddish-brown. Occasionally iridescent in a play of colors.
Chemical formula of limonite is FeO(OH) · nH2O
3. Hematite. As we can see silvery -brown- red colour of the sandstone.
4. It becomes solid as limonite becomes magnetic after heating up.