Test Reminder - Study Guide Solutions

Below is the key for the study given out in class today. If you are having a hard time reading the images, click on the images to enlarge them. Come in and see me before the test if you have any questions.

Below are the solutions to problems #6 and #8 of the calorimetry worksheet. Please finish the worksheet and the calorimetry lab for tomorrow, Friday, September 22nd, 2011.

Dance, Dance, Dance

I hope that everyone enjoyed the little dance lesson offered in class today. Remember, when I D.J. the homecoming dance, I had better see all my students movin' and groovin'. Let's review the parts of the "Molecular Motion / States of Matter Dance" or if you prefer "States of Matter / Molecular Motion Dance".
Part 1 - "The Solid" - Fists together and an ever so slight motion showing the molecules vibrating. The fists cannot move around one another nor can they move apart from one another. This shows the "vibrational motion" that all solid molecules have when subjected to energy.

• Definition - Energy - the ability to cause change. Changing the position of a molecule due to movement requires energy.

Part 2 - "The Liquid" - Fists are still touching one another, but they can now move around each other in a circular motion. Vibrational motion is still retained and movement of the fists around each other illustrates the "rotational motion" now afforded to the molecules. Rotational motion is achieved because enough energy is absorbed by the material to cause the vibrational motion of the solid to become so intense, the bonds that once held the molecules in place as a solid are broken.

• Definition - Temperature - the direct measure of molecular motion. A substance's melting point (solid to a liquid; vibrational motion to rotational and vibrational motion) is the molecular motion rate (temperature) that causes the bonds between the solid particles (atoms, molecules) to be broken.

Part 3 - "The Gas" - Fists are no longer touching and are moving in all directions in three dimensional space. Vibrational and rotational motion are still retained and the movement of the fists in all directions illustrates the "translational motion" now afforded to the molecules. Translational motion is achieved because enough eneryg is absorbed by the material to cause the rotational motion of the liquid to become so intense, the bonds that once held the molecules together as a liquid (touching, but able to move around each other) are broken.

• Analogy - "The Mean Uncle" - You are at a family outing and you are a young child. You go to your uncle, "Please swing me!" Your uncle abliges you, but before he grabs your hands to swing you around in a circle, he puts grease all of you hands and arms and his hands and arms. As he spins you round and round and picks up more speed, the weak bond that exists between you and him (greasy hands) is broken quite easily. You end up flying off into a bush. This is just like a liquid. The molecular motion becomes so great (high enough temperature), the bonds holding the liquid molecules together are broken and a gas is formed.

Just as energy can be placed into a material to increase molecular motion and break bonds, thus changing states of matter, energy can be removed (or lost) from a material. As energy is removed, the molecular motion decreases. The decreased molecular motion does not allow the particles (atoms or molecules) to overcome the attractive forces between them, thus bonds are formed between the particles.

**Molecular motion exists as long as there is energy. What is the name of the theory when no energy exists, thus no molecular motion exists in matter.

***Absolute Zero is the theoretical point when all energy has been removed from matter and no molecular motion exists for atoms of an element.

Book work for Monday, 9/12/2011

For homework, you are to read pages 55 - 65 (sections 3.1 through 3.5) in the textbook. At the back of the chapter, starting on page 74, answer the following questions: 1 through 5, 13, 14, 18, 21, 22, 25, 29, 33, and 34. The question #1 to start with is - How, in general, do we define matter?

Answers for Homework Questions Assigned on 9/12/2011

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.

Test Reminder

Below is a summary of all of the concepts that will be covered by the first major exam of the semester. You received back from me all of your work materials, so you have material to study from. On the calendar for the chemistry class, I have posted a key for the data analysis worksheet. You will not be performing any calcuator skills, only your comprehension of your data analysis skills will be assessed. Good luck and I will be at school early tomorrow moring, Friday, September 9th, 2011 if anyone has questions prior to the exam.

Partial Solutions Guide for the Conversions Packet

A pdf file for the conversions packet can by found on the class calendar under the date September 7th, 2011.