rob nobles [email protected] vhe 2015 “hands on chemistry” (with household items)
TRANSCRIPT
Hands on Chemistry (with household items)1. Density of solids and liquids2. Separations—Chromatography and Evaporation3. Learning to Count (MOLES) using oatmeal and candles4. Building Molecules with Marshmallows5. Acids and Bases—pH of common household liquidsBonus 6. Feel the Burn—calories in various foods
1. Density of solids and liquidsPurpose: A—to determine the density of various metals by displacement.
B—to determine the density of several liquids by use of a volumetric pipette.
Procedure A—to determin the density of various metals by displacement.
1. Find the mass of each metal using an scale. Record mass of each metal to the nearest 0.01 gm
2. Fill a 50 ml or 100 ml graduated cylinder about half-way with water. Record the volume of water in milliliters. (be sure to read the bottom of the meniscus).
3. Carefully place the metal into the graduated cylinder. It works best to tip the graduated cylinder and slide the metal cylinder along the side.
4. Record the new volume of water in the cylinder.
5. Determine the mass and volume of all four metals on your table.Metal Mass (gm) Volume (ml) Density (gm/ml)Copper pennies
Aluminum foil
Iron nails
Gold jewelry
Procedure— B—to determine the density of several liquids by use of a volumetric pipette.
1. Find the mass of a small empty container to the nearest 0.01 gm.
2. Use a dropper to measure 5.0 ml of tap water into the container and determine the new mass.
3. Repeat the process for all solutions and then calculate density. (Density = mass / volume)
4. Rinse all equipment with tap water when finished.
Liquid Mass of container (gm)
Mass of container with liquid (gm)
Mass of liquid (gm)
Volume of Liquid (ml)
Density (gm/ml)
Tap Water
Distilled Water
Rubbing Alcohol
Soda
Diet Soda
Others
• Conclusion from Part A: Organize the metals from most dense to least dense. What does this tell you about their atomic structure?
• Conclusion from Part B: Which solution was the most dense?___ least dense?____
• If you could float in rubbing alcohol what does that tell you about your density?
2. Separations—Chromatography and EvaporationPurpose--separate the colors in different markers using paper chromatographyProcedure—• Cut a 3 cm wide strip of paper towel long enough to hang in a glass of
water. Make a pencil mark 2 cm from the bottom. • Mark a chromatography paper with knowns.• Write the color of the marker on the paer in pencil.• Measure the length so the marker is not submerged in the liquid.• Tape the paper to a “hanger” so it can hang undisturbed for 30 min.• Remove and allow to dry.
Chrom--Calculate Rf values.Brand and Color of Marker
Distance spot 1 traveled D1 (cm)
Distance spot 2 traveled D2 (cm)
Distance solvent traveled Ds (cm)
Calculate RfD1/Ds
Calculate RfD2/Ds
Conclusion:1. Which Rf’s are most similar? Why?
2. What kind of solvent would you use for a permanent marker?
EvaporationPurpose—to determine the % of minerals in ocean water.
Procedure—1. Weigh an empty glass container that can be heated.2. Measure out 20.0 ml of salt water with the graduated cylinder.3. Pour into glass container and weigh.4. Heat on hot plate until all H2O has evaporated. 5. Be careful as you get to the end the salt will spatter and it is hot!!!6. Allow container to cool and weigh.
Trial 1 Trial 2 Trial 3
Mass of Empty glass container
Mass of container and salt water
Mass of salt removed
Mass of salt water used
Percent of salt in water (salt/salt water) *100
Average Percent
3. Learning to Count (MOLES) using oatmeal and candles
Purpose—To determine how many flakes of oatmeal are in a 1 gallon jar.
Prodecure—
Trial 1 Trial 2 Trial 3
Mass of empty weighing dish
Mass of 50 flakes of oatmeal plus weighing dish
Mass of 50 flakes of oatmeal
Mass of all the oatmeal in the jar
Solve for X flakes of oatmeal in jarRatio: (50 flakes/ ___ gm)= (X flakes / ___ gm)Solve for X Jars to hold 1 mole of oatmealRatio:___ flakes / 1 jar = 6.02x1023 flakes / X jarsConclusion: How many jars would it take to hold a mole of oatmeal? (Show all calculations)
PURPOSE: to burn candle wax and to determine the number of moles and molecules used up.
PROCEDURE:1) Mass a glass plate 2) Light a candle. Drip a little of wax on the plate. Stick candle to plate blow out candle. Find the total mass.
3) Light the candle and allow it to burn 5 minutes. Do not play with wax this will effect your results. Blow out candle and reweigh.
4) Calculate the new mass of the candle by itself.
Trial 1 Trial 2 Trial 3
Mass a glass plate
Calculate the mass of the candle by itself
Mass of candle and glass plate after burning 5 min
Mass of candle alone after burning 5 min
Mass of the candle that burned (left) in 5 min
CALCULATIONS
Wax is a mixture of hydrocarbons. C25H52 can be used as a representative hydrocarbon in the mixure. The burning of wax is shown below:
C25H52 + _____ O2 _____ CO2 + _____ H2O + energy
a) Balance the equation. Count atoms below.___________ carbon _______________________hydrogen_______________________oxygen____________
b) What is the molar mass of wax?c) How many moles of wax were in the candle before it burned ?d) How many molecules are in the candle before it burned?e) How many moles of wax were used up during the burning?f)How many molecules were used up during the burning?g) How long would it take to burn 1 mole of candle?
CONCLUSIONS 1) What 2 resources are used up as a candle burns?2) What has happened to the atoms in these resources?3) Is it possible to recover these 2 resources after they've been used? Explain
4. Building Molecules with Marshmallows (or other favorite candies)
Secrets of the Periodic Table• Objectives—to help students learn Lewis Dot Structures
for molecules.• Group 1 has 1 dot• Group 2 has 2 dots• Group 3 • Etc• Group 8 has 8 dots
• Learn how Lewis Dot structures help us build Molecules• Examples• Li• Be• B• C• N• O• F• Ne
You will need:Lots of Toothpicks and lots of mini marshmallows (or other candies)1. Using the toothpicks and marshmallows create a water molecule.2. Draw the lewis Dot Structure including all electrons3. Be sure to label the atoms and the shape of the molecule
Chemical formula
Lewis Dot Structure Shape
BeF2
H2O
AlCl3
NH3
CH4
Objective 3: Learn the primary shapes of molecules
Linear—BeF2
Bent—H2O
Trigonal planar—AlCl3
Trigonal pyramidal—NH3
Tetrahedral—CH4
Vitamin B12
Monster Molecules for FUN
5. Acids and Bases—pH of common household liquids
Purpose: To determine the pH of some household liquids.Procedure:• Obtain a small amount of liquid in a container (cup or bowl)• Using pH paper dab a piece of paper in the liquid and compare the color to the color chart.• Record the pH.
Discussion:
Summarize your results in a couple of sentences.
What types of molecules are acidic?
What types of molecules are basic?
Which solution had the lowest pH? _________What does that tell about the Hydrogen ion concentration?
Which solution had the highest pH? _________What does that tell about the hydrogen ion concentration?
Solution Prediction (Acid or Base) Measured pH
Bonus 6. Feel the Burn—calories in various foods
Food 1 Food 1 Food 1 Food 2 Food 2
Food 2
Mass of Food Before burning (gm)
Mass of Food After burning (gm)
Temp of water before (Celsius)
Temp of water after burning (Celsius)Volume of water used in can (ml)
Objective—to determine the number of calories in various foods.Procedure-- • Set up the apparatus as shown and weigh a food item.• Add 200 ml of water to the can and take the temp.• Burn the food, recording the maximum temp and weigh burnt food.• Repeat 3 times for each food.
• Calculations: • energy in food = mass of water used * specific heat * change in temp / change in mass of nut• q = (m*c* t) / (mass of nut)
Food 1 Food 1 Food 1 Food 2 Food 2 Food 2
Change in mass of food (gm)
Change in temp of water (C)
Mass of water used (kg)
q=energy in food (Kcal / gm food)
Average energy in food 1: _____Average energy in food 2:______Which food had the most energy?
Resources
• PhET—University of Colorado, virtual labs• World of Chemistry—online videos• Bozeman Science—online videos