Physical Science 9 Unit 4: Organizing the Elements: The Periodic Table #2A: Creating Color Pre-Lab #2A To Begin Remember to add important ideas/concepts/notes in the Unit 4 section of your comp book. How are colors produced from fireworks? Colors in fireworks are produced by the emission of energy from atoms and molecules. As the fuel source burns, energy is transferred from the burning fuel to the chemicals in the fireworks. The chemicals absorb the energy and release (emit) some of that energy in the form of visible light. Each chemical in the fireworks produces a distinct color of light. A similar process occurs when you heat a chemical in a flame. We will be testing 5 different solutions of ionic compounds in a flame and observing the distinct colors that are produced (ionic compounds are called “salts” because of their ability to dissociate into their positive and negative ions). Different colors of visible light are directly related to the amount of energy being emitted. Blue light, which has a shorter wavelength than red light, has more energy associated with it than with the emission of red light. Learning Goal Students will be able to… Describe of the unique properties of ionic compounds. Describe the safety concerns associated with this lab. Light a Terrill Burner, safely! Process and Procedure: Pre-Lab 1. A neutral sodium atom (Na) has 11 protons and 11 electrons. How many electrons does its positive ion have?____ Draw a diagram of the positive ion, sodium (Na 1+), where you show both protons and electrons. 2. A neutral chlorine atom (Cl) has 17 protons and 17 electrons. How many electrons does its negative ion have?____ Draw an atomic diagram of the negative ion, chlorine (Cl 1-), where you show both protons and electrons. Confirm your ideas with your table group as you diagram these ions. Sodium Ion (Na+1) 3. Discuss with your group the differences and similarities between these concepts: charge, ion, and atom. It is very important that each person understands that these are related concepts and NOT interchangeable terms. Use the 3 terms in one sentence: Chlorine Ion (Cl-1) _________________________________________________________________________ 4. Carefully observe each solution displayed on the front demo bench and do the following: a. Describe the color and clarity of all 6 salt solutions in the table below. b. Beneath each description, write the chemical formula for each solution. c. Write the appropriate dissociation equation for each salt (ionic compound). Chemical Name Sodium Chloride Potassium Chloride Cupric Chloride Lithium Chloride Calcium Chloride Strontium Chloride Description Chemical Formula Dissociation Representation 5. By yourself, use your prior learning about ionic compounds in order to prepare for this activity. Complete the statement below using full, detailed explanations (refer to material from last unit). a. I think each salt forms an ionic solid (crystal lattice) because… b. I can use electrical conductivity to test whether each solution contains ions because…. c. I think ionic crystals dissolve in water because at the microscopic level…. d. Positive ions in each salt solution are found on the __________________ (right side or left side?) of the Periodic Table and are classified as_________________________________________ (what group/groups are they associated with?). e. Negative ions in each salt solution are found on the ________________ (right side or left side?) of the periodic table and are classified as ____________________________________________ (what group/groups are they associated with?). f. Check in with your collaborative group to see how they responded to the above prompts. Make adjustments to your statements as needed. Safety 1. You will be placing small amounts of each salt solution in a flame and observing the color that is emitted. Draw a sketch of a Terrill burner’s flame. Label the “Coolest Part of Flame” and the “Hottest Part of Flame”. Your goal will be do transfer maximum energy to each salt solution…where do you think you should place the salt solution? Label this spot “Flame Test”. 2. In the space below, summarize the steps you would take to light the Terrill burner safely. 3. This lab activity has several safety issues of which to be aware. They are: a. Fire: Terrill burners will be lit at each lab station. Discuss with your group 3 precautions your group will take at each lab station (besides keeping long hair tied back). Write these in the space below: 1. 2. 3. b. Exposure to chemicals : All chemicals are potentially dangerous. Some of the ones being used are potentially more dangerous than others. Discuss with your group how you will protect your skin, eyes, clothing and other students coming after you to this lab station. Write these in the space below. c. Ingestion of chemicals (unintentional swallowing of chemicals): Discuss with your group one-way in which this could happen. What precautions could you take to prevent this from happening? Write the scenario and the precautions in the space below.