Law-Forums.org

[ardwyad]

Hi, I'm having a science test on 12/14/11 and I have some questions to ask before I have my test.
1. How can I distinguish between physical and chemical changes?
2. What are definitions and examples of an element and compounds?
3. How can compounds be decomposed into the elements that make them up?
4. How can compounds be synthesized from elements?
5. How do compounds have different characteristic properties than the individual elements that make them up?
6. How to use electrolysis to split compounds?
7. How can I test for hydrogen and oxygen?
8. Collect information about the characteristic properties of elements.
9. What are real life uses and the importance of various elements?
10. What does the periodic table classify elements according to their properties?
11. How can elements be catorgerized into two major groups: the metals and nonmetals?
12. How do metals have similar properties?
13. How do metals vary in their reactivity?
14. How is rusting a chemical reaction?
15. How do you identify the reactants and products in a chemical reaction?
16. How to conduct an experiment in which iron (Fe) reacts with oxygen?
17. How do I define the laws of conservation of mass?
18. How do I apply conservation of mass to phase changes, dissolving, and chemical reactions?
19. How do I recognize an open and close system?

Note: I know this is a lot of questions, but please I need good and detailed answers, I want to ace that test. So please work with me on this, please?
- Thank you very much (sincerely) :)

[bernd]

Since you want to "ace that test," let me suggest that you read through your textbook with your list of 19 questions and write out solutions and answers to the 19 questions as you read. You might also review your notes from class -- I am certain that you took notes during class, because you said that you wanted to "ace that test," and students who take notes will ace the test. If you have any questions that you still cannot answer, then speak to your instructor. Spend some time reviewing his or her view of the questions. Finally, if you want additional information, post your question AND all your comments from your textbook, your notes and discussions with your instructor and ask for additional information. I realize that you probably cannot accomplish all of this by 14 December. Next time, start the process earlier. You can take your notes from class and make summary notes at the end of each week. This will keep you up-to-date with the material.

This is how one aces a test. If you post the list of 19 questions that you should know the answer to and someone fills in the answer to all 19,you will learn very little.

This answer is working with you and not doing your for you. If you want to learn, you will have to accept the burden of doing the lion's share of the work.

To help you to learn, read the material; say the answers out loud; write the answers down; re-read what you wrote down. The process of reading, stating, writing and re-reading is what helps the brain to learn.

Good luck with your test.

[ailwyn]

System says my answer is too long, so I'm taking out a lot of it.

2. Only 92 elements occur in nature, though a few dozen others have been made in laboratories. The millions of compounds that can occur in nature are all composed of various combinations of the 92 naturally-occurring elements. The smallest possible particle of a compound is called a molecule; the smallest possible particle of an element is called an atom. Thus, a molecule is made of two or more atoms; the molecule will contain a whole number of atoms (not 3.64 atoms, for instance).
The 20 elements having the lightest atoms are hydrogen, helium, lithium, beryllium, boron, carbon, nitrogen, oxygen, fluorine, neon, sodium, magnesium, aluminum, silicon, phosphorus, sulfur, chlorine, argon, potassium, and calcium. Many of these form familiar compounds: table salt is made of sodium and chlorine; water is made of hydrogen and oxygen; gasoline (a mixture of compounds) is made mainly of hydrocarbon compounds, that is to say, its compounds are made of hydrogen and carbon; sugar is made of hydrogen, carbon, and oxygen; the compound that forms seashells is made of calcium, carbon, and oxygen.

3. If a compound is stable in a given environment (let's say, at a certain temperature and pressure), some energy must be added if one wants it to decompose quickly into its component elements. Examples of energy that can decompose various compounds are heat, UV light, and electricity.

4. Strangely, while the addition of energy may decompose a compound into elements, very often if two elements are stable in a given environment, some energy must be added to get them to combine into a compound. That's because the manner in which they combine involves the sharing of "electrons," which make up the outer shells of an atom; some heat may be required to make the electrons more energetic and hence more accessible to neighboring atoms.

5. Consider the case of table sugar, whose formula is C12H22O11. That means, each sugar molecule is made of 12 carbon atoms, 22 hydrogen atoms, and 11 oxygen atoms. These atoms are bonded together in a particle pattern, two rings with an oxygen in between. While pure oxygen and pure hydrogen are gaseous at room temperature, and charcoal can be made of nearly pure carbon, table sugar looks nothing like its component elements.

9. Almost everything you eat is made mainly of carbon, hydrogen, oxygen, and nitrogen. There will be trace amounts of other elements: iodine in seafood, iron in beef and spinach, potassium in broccoli and bananas and avocados, calcium in milk and cheese, sulfur in eggs. Your body needs calcium to build bone, iron to make red blood cells, potassium to regulate heartbeat.
Mankind has found innovative industrial or household uses for many of the elements: silicon in computer chips, boron in kitchen cleaning products, phosphorus in matches, aluminum in aircraft bodies and in shiny kitchen foil, lithium in tranquilizing drugs, neon and argon in light bulbs, copper wire for the efficient conduction of electricity, gold and silver in coinage, mercury in thermometers, helium for flotation (it's lighter than air).