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COMPOUNDING THE MATTER
Take a minute and think back to the discussion you and your classmates have been having about matter. Remember that matter is classified into two categories: mixtures and pure substances. The pure substances are divided into elements and compounds. You have already learned about mixtures and one type of pure substance: elements. In order to fully understand matter, which comprises everything around you, you need to know about compounds and their properties. Acid precipitation for example is caused by specific compounds which then combine with water in the atmosphere. So, what is a compound? In this investigation, you will discover the properties of compounds.
Objective Students will analyze substances in order to identify the properties of compounds.
Materials
Samples of compounds Periodic Table
Prentice Hall Science Explorer: Chemical Building Blocks: Activity 1
1. Examine the objects provided by your teacher.
2. Identify the properties that are unique to each object.
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3. Identify the properties that the objects have in common.
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4. All of the objects you examined are compounds. Construct a definition for the term compound, based upon your observations of the objects.
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Activity 2
5. Read “Compounds” on p.21 in Prentice Hall Science Explorer: Chemical Building Blocks in order to identify the properties of compounds and Complete Chart 1 on compounds as you read. Chart 1: Compounds
Definition / Properties / Representation / ExamplesActivity 3 Compounds are made when elements react chemically to form a new substance. The compound can be represented as a formula. For example, a snail’s shell is made mostly of calcium carbonate (CaCO3), a compound made from calcium (Ca), Carbon (C), and oxygen (O).
Calcium
CaCO3
Carbon
Oxygen
Adapted from Prentice Hall Science Explorer: Chemical Building Blocks
7. Determine the elements that make up the following compounds using the Periodic Table.
a. water (H2O) ______
b. glass (SiO2) ______
c. table sugar (C12H22O11) ______
Another way that compounds can be represented is through molecular diagrams. See figure 1. In the diagrams, the circles represent molecules. The molecules of sodium have combined with the molecules of chlorine to form the compound sodium chloride, or table salt.
Figure 1
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Diagram A Diagram B Diagram C
Sodium Chlorine Sodium Chloride
8. Which diagrams are representing the molecules of an element? ______
9. Which diagram is representing the molecules of a compound? ______
10. Explain why the molecules of sodium are shown as being linked with the molecules of chlorine in the diagram of sodium chloride, diagram C.
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11. Draw a molecular diagram of the compound hydrochloric acid that is formed when the element hydrogen reacts with the element chlorine.
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Hydrogen Chlorine Hydrochloric acid
Analysis
1. Your neighbor is outside grilling steaks in January. You realize that the propane fuel he is using to heat the grill is a compound. Describe the properties of propane (C3H8), based on the fact that it is a compound. Use information from the reading to support your
response.
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2.
A B C
_____ 1 Which diagram best represents the Kool-Aid mixture?
_____ 2 Which substance is best represented by Diagram “B?”
A Element B Compound C Atom D Mixture
Debate Diary #8:Acid precipitation is formed from the compounds sulfur dioxide (SO2) and nitrogen oxides (NOx). Which elements have combined to form those compounds? Explain how the properties of the elements compare to the properties of the formed compounds.