Below are the answers to the problems assigned from the book on Monday, September 12th, 2011.
1. Matter is the "stuff" that occupies space and has mass.
2. Physical states of matter are solid, liquid, and gas.
3. Gases are very compressible.
4. Liquids have a definite volume, but can take on the shape of the container that hold them.
5. Solids are held together the most rigid and can only vibrate next to each other. Liquid molecules touch one another, but can move around each other. Gases can move around and apart from one another.
13. Before question 13 is answered, I want to define the term aqueous. An aqueous is a type of state of matter when a substance is dissolved in water. A physical property of nickel (II) sulfate in solution is a bright green color.
14. A chemical property of nickel (II) sulfate is that it will react with barium form a barium chloride solution to form a white precipitate of barium sulfate. Precipitate is a scientific way of saying a solid was formed.
**The answers to question 18 have explainations with them. You are not required to give the reason for either physical or chemical change, only indicate the type of change. I just added the explainations for the sake of understanding.
18. a. chemical change - the burnt fabric of the shirt will change colors and gases will be released by the burning of the fabric.
18. b. physical change - the gas does not change within the tire, but rather just occupies a smaller volume due to the cold temperatures.
18. c. chemical change - the silver reacts with oxygen in the air to produce a new compound (silver oxide) that appears black in color.
18. d. chemical change - the alcohol in the wine reacts with oxygen to for vinegar (or also called acedic acid).
18. e. chemical change - the physical properties of the grease change. Also, the soapy material would have bubbles within it, indicating the production of a new state of matter, gas.
18. f. chemical change - the leaking of the battery is not in itself a sign of chemical change. The fact that it cannot be recharged (charging is a chemical change) is an indicator that a chemical change has occured. The leaking is probably the result of a new state of matter being produced by the chemical reaction and the design of the battery cannot contain the new substance.
18. g. chemical change - tooth decay is a change in the chemical make-up of the tooth. The acids from the bacterial cause this change.
18. h. chemicale change - related to the sulfuric acid / sugar demonstration done in class. The charring is a result of the sugar burning. Anything that burns undergoes a chemical reaction.
18. i. chemical change - the hydrogen peroxide fizzing (effervescing) is a result of a gas being released from a chemical reaction. This reaction described in 18 i is the reaction for elephant toothpaste done on the first day of class.
18. j. physical change - the term dry ice comes from the fact that solid carbon dioxide (dry ice) goes directly from the solid phase to the gas phase, skipping any liquid that could be produced. This process is called sublimation. The chemical composition of carbon dioxide never changes.
18. k. chemical change - the color change of the fabric is the indicator of the chemical reaction occuring.
21. Elements form compounds.
22. Compounds can be broken down into the component elements by chemical change.
25. A pure substance is a element or compound with a fixed composition. Only that element or compound is in the container. A mixture is not a fixed composition. A mixture can have any number of elements or compounds in the same container.
29. a. The air that you breathe is a mixture. Air consists of different elements in compounds. The main component of air is elements nitrogen (N2), which makes up roughly 75% of the gases in the atmosphere. Elemental oxygen (O2) is roughly 20% of the atmosphere. The remaining percentage are small amounts of carbon dioxide, argon gas, sulfur dioxides, etc, etc.
29. b. A soda is a mixture. The carbon dioxdie dissolved in the soda is a visible component of the mixture as it bubbles out. The sugar that is dissolved in the water could be separated by evaporating away the water. All components of soda can be separted from each other into pure substances.
29. c. Water is a pure substance. It is the chemical combination of two hydrogen atoms and one oxygen atom. Water has consistent properties and cannot be changed as long as the two to one ration of hydrogens to oxygen exist.
29. d. A diamond is pure carbon (not quite an accurate statement). A diamond is considered to be one very large molecule. Therefore; diamond is a pure substance.
33. Distillation can be used to separate two liquids in a mixture. The two liquids must have different boiling points in order to achieve this. An example would be to separate ethanol from watere. Ethanol will boil at a lower temperature thatn water. This concept was covered in the demonstration given on Tuesday, September 13th, 2011.
34. Filtration can be used to sepate anything that can dissolve in a solvent (i.e. salt in water) and a substance that will not dissolve in the same solvent. An example would be to separate ground up glass from sugar. The sugar could dissolve in water but the ground glass could not. The mixture could be passed through filter paper. The ground glass would stay in the filter paper and the dissolve sugar would pass through. The water could be evaporated to collect the solid sugar again.
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