Light and Energy – Flame Test

Agenda  Objective: SWBAT identify an unknown atom in solution using the color emitted when heated and complete post-lab questions using the mathematical relationships between energy, frequency, and wavelength of light.  Agenda:  Warm-up  Introduction to visible light emission  Flame Test Pre-lab Questions  Flame Test  Flame Test Post-lab Questions *Today is the LAST day to turn in late work for this six weeks*

Warm-up Answer warm-up questions on Pg 24 of your notebook  What is the relationship wavelength and frequency?  What is the relationship between frequency and energy?  What has a shorter wavelength red or yellow light?  Which has more energy Blue or Yellow?

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Science behind light.  Salts are electrically neutral compounds that are composed of both positively charged ions and negatively charged ions.  Example:  Table salt consists of both positive sodium ions (Na + ) and negative chloride ions (Cl – ).  Metal salts are used to produce the vivid lights in fireworks!

What causes light/color to be released from metal ions?  The heat from the ignition (flame) causes an influx of energy into the metal atoms. As heat gets absorbed by the metal atoms, electrons that are circling around the lower orbitals of the atomic nucleus excite and jump to a higher energy level.  These electrons do not stay in excited states for long - as the heat dissipates, they soon fall back to their ground states, and give off the extra energy in the form of light energy.

Why do we see different colors for different metal ions?  Light travels in waves.  Different metal atoms produce different colors of light when excited because the light that they emit is traveling at different wavelengths.  The wavelengths of light produced by metals vary due to the amount of energy that is released by the unique arrangement of electrons in the atom as electrons fall from an excited state back to a ground state.

Visible light on the electromagnetic spectrum  When metal salts emit short wavelengths of visible light in the range of 400 to 500 nanometers, they produce violet and blue colors.  When metal salts emit longer wavelengths of visible light in the range of 600 to 700 nanometers, they produce orange and red colors.  Yellow and green colors are produced by metal salts that emit visible light at intermediate wavelengths (500 to 600 nanometers) along the electromagnetic spectrum.

Lab Groups (Period 2)  Group 1 1. Reed 2. Alexi 3. Ella 4. Jake B.  Group 2 1. Ambika 2. Omar 3. Justin 4. Rachel  Group 3 1. Sophia 2. Logan 3. Elijah 4. Sheradyn  Group 4 1. Isaias 2. Andres 3. Leah 4. Jacob  Group 5 1. Summer 2. Alex R. 3. Ilse 4. Alex H.  Group 6 1. Josiah 2. Carly 3. Caleb 4. Aaron

Lab Groups and Roles  The numbers above represent the role that you will be playing in your group: *Note all roles must actively participate and positively contribute to your lab group* 1. Group Facilitator  Keeps everyone on task and focused  Ensures everyone knows what goes in the notebook and where it goes  Leads discussion of pre- and post-lab questions 2. Safety Manager  Makes sure everyone keeps goggles on at all times and are not engaging in off-task or unsafe behavior  Makes sure gas/Bunsen burner is turned off at the end of the lab 3. Materials Manager  Responsible for getting the goggles for each person in your group  Makes sure goggles and lab aprons are put away at the end of lab  Cleans lab bench at the end of lab – wipe any excess water off lab bench. 4. Spokesperson/Assistant Group Facilitator  Relays group answers to pre or post-lab questions during class discussions  Ensures that each student gets the opportunity to participate in the laboratory (everyone gets a chance to use the loop and the flame)  Aids group facilitator in keeping group focused and on-task

Flame Test Lab Notebook Set up  You will take turns reading the introduction to the lab in your group  Once you have finished reading the introduction, you will begin your lab write-up on page 24 and 25 of your notebook. (*Note you can write the title and begin the lab report below your daily warm- up)  You must include:  Names of all group members, Date, and Period (3 pts.)  Title (3 pts.)  Purpose (3 pts.)  Pre-Lab Answers (18 pts)/ Answer in complete sentences  Table (20 pts.) – you must write this in your notebook  Post Lab Answers (50 pts)/ Answer in complete sentences  Once you have properly set up your notebook you can begin answering the pre-lab questions

Flame Test Lab Safety Information  Wear goggles at all times.  You must tie long hair back (see me for hair tie if needed)  No Horseplay – anything I see that I feel is unsafe and/or places you or your classmates in danger will result in your removal from the lab. If you are removed from lab you will be required to work on bookwork for the rest of the class period.  When collecting the metal solution with your loop, gently dip the loop in the beaker. Do not place the entire metal wire in the beaker or bend the wire.  Place only the wire loop in the flame  ALWAYS be aware of the flame – do not reach over it, or clutter your lab area with paper