Before this lesson: (prerequisite knowledge) Prior to these lessons students learned how to calculate density of a regular and irregular shaped object, define mass and volume, and convert between different units each. Students then learned the difference between homogeneous and heterogeneous mixtures, and performed a chromatography lab. Students were then introduced to the periodic table and the Bohr model of the atom. Student learned the theory behind the Bohr model and atomic spectra, and learned to calculate frequency, wavelength, and energy of a photon. Students also know the difference between a cation and anion. They also know how atoms bond and the difference between covalent, ionic, and metallic bonds. In this lesson: In this lesson, students will learn to explain how mass spectrometry works, and analyze fragment patterns from mass spectra data to identify different substances. They will also perform a density test to identify a substance, calculate percent error, perform a flame test lab to identify metallic cations, apply their skills and lastly, calculate the frequency and energy of the light that they observe.

Review! 1) Which phone booth is the most dense? 2) Which is the least dense? Why? Many particles Same Space = High Density Fewer particles Same Space = Low Density

Density Review Every object has a specific density. We can use the property of density to identify a substance. Densities of some metals (g/cm 3 ) Aluminum 2.70 Copper 8.96 Lead Iron 7.87 Magnesium 1.74 Zinc 7.13 Remember, when a substance is a solid, we use g/cm 3 as the units. For liquids, we use g/mL

Density Lab Purpose: To determine the composition of metals before and after U.S. pennies have been composed of copper and zinc since 1959, but the ratio of copper to zinc has changed over the years because of increases in the price of copper. Copper and zinc are both metallic elements, and they share many physical properties, but they have different densities. By measuring the density of pennies from different years, it’s possible to track changes in the penny’s composition. Which method of finding density will you use in the penny lab? The water displacement method as a penny is too small to use standard ruler measurements.

Review: Using the Displacement Method to Determine Density The amount of matter in something is measured using an electronic scale. Steps: 1.Turn scale on. 2.“Zero” the scale before measuring an object’s mass. 3.Place the object on the scale using weigh paper * UNITS:__________ grams

The Displacement Method 1)What is the density of object “A”? 2) What is the density of object “B”? OBJECT AOBJECT B Always read the volume at eye level—where the meniscus is.

Calculation Ex. 1: A piece of metal: 36.2 g, Volume of water alone = 29.9 mL, Volume of water with metal A = 36.1 mL a) volume = ____________________________________________ b) Mass=___________ c) density = __________________ d) Will object float or sink in water (density of water= 1.0 g/mL)? 36g = 6g/cm 3 6mL 36g Final Volume – Initial Volume= Volume of Metal 36mL – 30mL= 6 mL SINK! Because the density of the metal is greater than the density of water Remember: 1 mL = 1 g/cm 3

A ring made of 24K gold: g, Volume of water alone = 20.0 mL, Volume of water with metal A = 66.9 mL a) volume = _______________________________ b) Mass=___________ c) density = ________________________ Ex. 2

Percent Error Percent Error: The difference between Approximate and Real Values, as a percentage of the Real Value. Allows you to see how accurate your measurements and calculations are. %Error Formula: Experiemental Value – True Value x 100% True Value What is your percent error for the density of gold in ex. 2? What are some reasons that might account for the error in your value?

Percent Error %Error Formula: Experiemental Value – True Value x 100% True Value We do: A student determines the experimental density of aluminum to be 2.3 g/cm 3. What is the student’s percent error?__________________ What might some sources of error? You + Partner do: A student measures the mass of a piece of iron to be 5 grams. But, the true mass, is 5.3 grams. What is the students perent error? ___________________What might be some sources of error? You do: A student measures the length of a wire to be 3.2 cm. If the true length is 3.5 cm, what is the students percent error? ___________________What might be some sources of error?

Penny Lab Handout Read quietly Watch me model how to do the lab Questions? Homework: Summarize parts 1-4 of the lab handout. This is your pre-lab and should be written in your lab notebook. Due: Next Class Session “Lab Title”, Name, Partner, Date 1.Intro/background 2.Materials 3.Procedure: write out each step 4.Data tables (draw in lab book)

Day 2-Exit Slip : A student measures the volume of water in a graduated cylinder to be 40 mL. She drops a 5 gram piece of aluminum into the cylinder, and the volume increases to 42 mL. What is the density of the student’s piece of aluminum? What is the student’s percent error if the true density of aluminum is 2.70 g/cm 3 ?__________________ What might be some sources of error?

Penny Lab Data Post your group’s data on the white board. Discussion Topics: 1)Why didn’t everyone get the same results? 2)What are some limitations of using the density test to identify a substance? 3)How is the density test different from mass spectrometry?

Day-3-Flame Test Lab Report Homework Lab Report: Complete everything but #5 before the lab 1)Give the lab a title in your composition book 2)Answer Flame Test Pre-lab questions in comp book. (write question and answer). 3)Summarize parts 1-4 of the lab 4)Draw your data table 5)Answer questions in your conclusion and discuss the theory behind the experiment. (after lab)

Day 4- warm-up 1.Identify each fragment 2.Which molecule is represented by the fragment below? 3.Give an example of when it might be appropriate to use density to determine the identity of a substance, and when mass spectrometry would be better?

Review: Why do atoms emit light? 1)Ground State: Lowest energy leave allowed in an atom 2)Excited State: higher energy levels in an atom Niels Bohr: electrons are only allowed to exist in certain “orbits” around the nucleus. When atoms Absorb energy, the can jump from Ground state to the Excited state. The electron then falls back to Ground state and emits energy in the form of EM radiation. ELECTRON GROUND STATE ABSORBS ENERGY EXCITED STATE

The ATOM…quick review (don’t write down) has 2 regions – nucleus – shells 3 subatomic Particles – Protons (+) – Neutrons – Electrons (-)

Review: Shell drawing rule… 1 st shell holds up to 2 e- 2nd shell holds up to 8 e-

Photons = Light or Electromagnetic Energy Review

Ground State H n=1 n=2 Photon!

Bohr Model e- Can gain energy by moving to a higher energy level e- Can lose energy by moving to lower energy level

Review R O Y G B I V

Frequency Frequency (ν) High Frequency Wave Low Frequency Wave

Light = electromagnetic (EM) radiation. All forms of light have: a)Wavelength b)Frequency c)Constant Speed Electromagnetic Spectrum

PROPERTIES OF LIGHT Definition Symbols /Units Equation to find: Wavelength Distance light travels from one low point to one high point. Distance covered before wave repeats itself. λ (lambda) Units: Meters (m), *convert nanometers (nm) λ= c/f Frequency Number of times a wave repeats itself per second f or ν (nuu) Units: Hz = s-1 = cycles/second f= c/λ Speed How fast light travels in a vacuum. = 3.00 x 10 8 m/s c Units: m/s c=λf

b) Frequency (“ν”) Frequency: number of times a wave repeats itself per second Symbol: ν Units: s -1, or Cycles - s -1 (=cyles/second) or Hz Low Frequency Wave Higher Frequency Wave= = BIG WAVES =SMALL WAVES

c) Speed of Light (“c”) Speed of Light: is a CONSTANT (in a vacuum ) = 3.00 x 10 8 m/s * (186,000 miles/second) Symbol: c Units: meters/second (m/s) Definition:

Formula ν = c λ Frequency (s -1 ) Speed of Light= 3.00 x 10 8 m/s Constant Wavelength (m )

Ex. 1: Find the frequency of a green light that has a wavelength (λ) of 545 nm. ν = ? λ = c = Review Problem #1 ν = c λ 3.00 x 10 8 m/s 545 nmX 1.00 x m 1 nm = x m ν = 3.00 x10 8 m/s x m = 3 x10 8-(-7) /s 5.45 = 3 x10 15 /s 5.5 =.54 x /s = 5.4 x s -1 Remember Units!! Hz is same as s -1 (= 1/s)

Ex. 2: Find the wavelength of electromagnetic that has frequency of 3.00 x s -1. What type of radiation is this? ν = 3.00 x 10 9 s -1 λ = ? c = Review Problem #2 λ = c v 3.00 x 10 8 m/s λ = 3.00 x10 8 m/s 3.00 x s -1 = 3 x m 3.00 = 1.00 x10 -2 m ν = c λ ÷ X λv = c λ = v λv Microwaves

Ex. 3: Find the wavelength (in nm) of electromagnetic that has frequency of 2.15 x Hz. What region of the EM spectrum does this represent? ν = 2.00 x Hz λ = ? Review Problem #3 c = 3.00 x 10 8 m/s λ = 3.00 x10 8 m/s 2.00 x s -1 = 3 x m 2.00 = 1.5 x10 -9 m ν = c λ ÷ X x-rays = 1.5 x10 -9 m x 1.00 x 10 9 nm = 1.5 nm m

EM SPECTRUM Radio Wave- Microwave- IR –– UV – X-rays –Gamma- Cosmic λ gets smaller  ν gets bigger  ENERGY gets bigger  Big Wave Length = Small Frequency = Small Energy Small Wave Length = Big Frequency = Big Energy VisibleVisible Know these relationships

Flame Test Lab Demo What safety precautions do you need to take? What colors do you observe for the following ions? (take notes) K + Cu 2+ Li + Na + Cu 2+ Ba 2+ Sr 2+