chem mystery - behs science · chem mystery 11 student number ... read pages 56 through 60 in...

Chem Mystery 11

Student Number _________________

Hour ______

Chem Mystery

“My Word! It is Professor Dickle! Weinberg, see if you can make out what the devil he was working on,

and the rest of you get back to your stations.”

Chem Mystery 2

Unit Objectives

1. KNOW and EMPLOY safe laboratory practices.

2. DISTINGUISH between accuracy and precision.

3. Accurately DETERMINE physical measurements with the correct number of significant digits.

4. APPLY the concepts of area, volume, mass, temperature and density to common science problems.

5. In a laboratory setting, CALCULATE the density of solid objects.

6. CALCULATE the percentage error from given data.

7. CONVERT between metric unit prefixes involved in measurements of mass, volume and length.

8. INFER from demonstrations the parts of the Kinetic Theory of matter.

9. IDENTIFY examples of Brownian motion and diffusion.

10. IDENTIFY the major parts of scientific method: stating a problem, obtaining information, forming a hypothesis, conducting an experiment and stating conclusions from the results.

11. APPLY knowledge of experimental design by correctly IDENTIFYING and DIAGRAMING the independent variable(s), dependent variable(s), constant(s), control group and the number of repeated trials.

12. DESIGN, CONDUCT and EVALUATE a scientific investigation.

Chem Mystery 3

Measurement Again Accuracy: How close a _______________ comes to an __________________________ value. Precision: How close a ______________ of similar ________________________ comes to

___________other (reproducibility).

Significant Figures All the ____________ in a measurement that can be _______________known plus an ________ digit that must be ____________________.

Rounding Rule Measurements or _________________ cannot be _______ precise than the _____________ precise measurement and should be _______________ .

Read pages 56 through 60 in Chemistry Visualizing Matter, then answer the following:

1. Which graduated cylinder shown in Figure 217 would you selected for measuring 17.5 mL of a liquid?

2. Define accuracy.

3. What are significant figures?

4. How would you round a multiplication calculation?

5. How would you round an addition calculation?

0 100 200

0 10 20 30 40 50 60 70 80 90 100

1 0 2 3 4 5 6 7 8 9 10

0.1 0 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

1 2 3 4 cm

20

30

1 2 3 4 cm

Chem Mystery 4

EXPERIMENTAL ERROR AND PERCENTAGE ERROR

The experimental error is calculated by _________________________ the _______________ value from the __________________ value (E = OA).

The ________________________ error is the comparison of the experimental error to the accepted value expressed as a percentage. The sign of the error may be either positive (the experimental result is too__________) or negative (the experimental result is too ______________).

% Error = Observed Accepted X 100 Accepted

UNITS The Language OF Science

1. The___________(m) is the SI unit of length measurement. There are __________ centimeters (cm) in a meter.

______________ is a measurement of the number of squares ( i.e.______ ) that fit into a twodimensional object. DRAW A CM 2 HERE:

2. __________ is a measurement of the number of cubes ( i.e.______ ) that fit into a threedimensional object.

The_________ (L) is the SI measurement of volume. There are 1,000 millimeters (mL) in a liter. A __________ is the same as a________. DRAW A CM 3 HERE:

3. __________________ is anything that occupies space. Mass is the _______________ of matter present.

The SI unit of mass is the ___________________ (Kg) which is defined as the mass of 1,000 cm 3 (mL) of water at 4 o C. There are _________________ grams (g) in one kilogram.

4. Density measures the amount of ________________ in a given unit of __________________. The units for density are _____________ or ____________. Density is defined as mass/volume.

5. Water has a density of ________________. If an object is ____________ dense than water, it will sink. A sunken object displaces its _______________ in water. If an object is _____________ dense than water, it will float. A floating object will displace its _____________ in water.

Units of Length _____________ Volume ____________ Measurements Mass _____________ Temperature ____________ in the Metric System Heat _____________

Prefixes kilo __________ times larger centi __________ times smaller milli __________ times smaller micro __________ times smaller

Chem Mystery 5

Measurement Madness TABLE 1: DENSITY OF LIQUIDS

Water Liquid A Liquid B Liquid C

Mass of empty pipette _________ _________ _________ _________

Mass of pipette and liquid _________ _________ _________ _________

Mass of liquid _________ _________ _________ _________

Volume of liquid _________ _________ _________ _________

Density of liquid _________ _________ _________ _________

TABLE 2: DENSITY OF SOLIDS

Solid A Solid B Solid C

Mass of empty boat _________ _________ _________

Mass of boat and solid _________ _________ _________

Mass of solid _________ _________ _________

Water volume at start _________ _________ _________

Water volume after _________ _________ _________ solid is added

Volume of solid _________ _________ _________

Density of solid _________ _________ _________

% Error = Observed Accepted X 100 Accepted

CONCLUSIONS

1. Make a drawing of your fourlayer liquids. Label each liquid and give its density.

2. How could you find the volume of an irregular solid that floats in water?

Chem Mystery 6

Kinetic Theory of Matter Demonstration Notes:

1.

2.

3.

4.

5.

States:

1. All __________ is made up of extremely small __________.

2. Between the particles is empty ___________.

3. Particles are in ____________ random ___________.

4. Motion suggests ________________.

The energy an object has because of its particle _________ is _________ energy.

______________ is a measure of the average kinetic energy (speed) of the

particles in an object. The _______ for temperature are o K, o F, o C.

The temperature at which the _________ of particles ceases is known as ___________ zero.

_______________ is the random movement of very small particles suspended in a fluid that results from collisions with molecules.

____________ is the ability of one substance to penetrate into a mass of particles of another substance.

The _____________ of a gas in a closed container can be explained by the movement of molecules and their collisions with walls of the container.

Chem Mystery 7

Scientific Method 1. Stating a _________________ something is considered a problem if its solution is not obvious.

Some crucial information is missing. Solving the problem involves finding this ___________ information.

2. _______________ information on the problem the more you know about the problem the more _______________ you can state the problem and the less time you will waste looking for solutions.

3. Making a _________________

a. Use what you know about the problem to ________________ a solution and try it. b. Look for ________________ that will help you make predictions about the problem,. c. Make a ____________, or a representation, of what you’re working with. d. Break the problem ____________ into smaller, simpler problems.

4. _____________ an experiment design an experiment that will provide a means for you to make a solid ______________ on your hypothesis

5. Make a ________________ a solid conclusion is related to the hypothesis and based on the _________ of a well designed experiment.

EXPERIMENTAL DESIGN CONCEPTS

A science experiment is designed so that only _________ variable is being tested at a time. A ____________ is something that is changed to study how this change affects the time being studied. By changing only one variable, when you make your conclusion you can be assured that it is only that one variable that is causing the ____________.

1. Independent variable (IV) the variable that is purposely ______________ by the experimenter.

2. Dependent variable (DV) the variable that responds and is the variable ______________.

3. Constant (C) all factors that are kept the _____________ during the experiment.

4. ____________ the standard to _______________ the experimental effect against.

5. Repeated trials the ________________ of objects/organisms undergoing treatment for each value of the independent variable, or the number of _______________ the experiment is repeated.

Chem Mystery 8

Scenario One: The amount of vitamin C in orange juice. Description: Erica’s chemistry class was studying a unit on acids and bases. They investigated the amount of absorbic acid (vitamin C) in a solution. Erica’s laboratory group decided to experiment with the amount of vitamin C in types of orange juice. The types of orange juice they experimented with were fresh, frozen, and bottled. They collected 100 mL of fresh squeezed juice. They mixed up 100 mL of frozen juice as directed on the package. They purchased 100 mL of orange juice from the vending machine in the cafeteria. Using an established procedure, the students measured the milligrams of absorbic acid in each sample of juice.

Problem: Possible Hypothesis: IV: units Trt: # trials: DV : units

C's :

Ways that the experiment could have been improved?

Scenario Two: The effectiveness of water sealants Description: Jake’s family had recently built a new deck for a hot tub. He wondered which brand of water sealant would best protect the wood decking from absorbing water splashed from the hot tub. Jake performed a test by cutting small blocks from the decking material. He dipped two blocks in each of one of three major brands of sealant and allowed it to dry for two days. He massed each block. Jake placed the blocks in hot tub water overnight. He massed each block again, finding the difference in the masses (grams). He concluded the difference was the amount of water absorbed.


C's:


Chem Mystery 9

Scenario Three: The rate of a metal reaction is affected by the concentration of acid. Description: Susan found that magnesium reacts with hydrochloric acid. She observed that the metal disappears as the acid reacts with it. She found that many bubbles were released as the reaction happened. She wondered if changing the concentration (strength) of the acid would affect how fast the reaction occurred. Susan prepared five concentrations of hydrochloric acid, .25M, .5M, 1M, 2M, 4M. She placed a piece of magnesium in each concentration and described the intensity of the reaction as fast, moderate, or slow. She also recorded color changes in the metal as the reaction occurred. She repeated the procedures four times for each concentration of acid.


C's:


Scenario Four: Which kind of metal gives the most voltage in a battery? Description: Tyler was studying batteries. He discovered that a battery works as electrons flow between two dissimilar metals through a solution. He wanted to find out what common metal combinations would give him the highest voltage measurements. He decided to test copperiron, copperaluminum, copper zinc, ironaluminum, and ironzinc. He cut out strips of various sizes of the metals. Tyler prepared three different weak salt solutions. He placed each pair of metals into 50 mL of the solutions and measured the voltage produced, using a voltmeter. Tyler conducted three trials in each of the three different solutions with each pair of metals.

Problem: Possible Hypothesis: IV: units Trts: # trials: DV : units

C's:


Chem Mystery 10

Scenario Five: The effect of salt on the freezing point of water. Description: Amy was performing a special project in chemistry dealing with salt and the freezing point of water. Amy prepared .5%, 2.5%, 6% and 10% salt solutions. She put some ice in a styrofoam container. She placed a test tube of each solution one at time into the ice and began to make it freeze by turning it around and around in the ice. When the solution in the tube turned to slush Amy took the temperature with a thermometer.


C's:


Practice with experimental design

1. _____

2. _____

3. _____

4. _____

5. _____

6. _____

7. _____

8. _____

9. _____

10. _____

11. _____

12. _____

13. _____

14. _____

15. _____

16. _____

17. _____

18. _____

19. _____

20. _____

21. _____

22. _____

23. _____

24. _____

25. _____

Chem Mystery 11

Mystery Lab Experimental Design Box:

Procedures:

Data Table:

Chem Mystery 12

Graph:

Conclusion:

Title:

Chem Mystery 13

Measurement Practice Percent Error

Every measurement is a comparison of a physical quantity with a standard or unit of measurement. To check the validity of your experimental values, you can determine the percent error between your value and the theoretical or literature value. Find the percent error in each of the following problems.

1. The literature value of the atomic mass of an isotope of nickel is 57.9 g/mole. If a student determined the mass to be 59.6 g/mole, what was the percent error?

2. At 20 o C, the solubility of potassium chloride is actually 34.7 grams per 100 cm 3 water. A laboratory experiment yielded 32.3 grams per 100 cm 3 water at 20 o C. What is the percent error?

3. What is the percent error in a measurement of the boiling point of naphthalene (C10H8) as 221.0 o C, given that the literature reports the value as 217.9 o C?

4. A student measures the density of beech wood as 0.741 g/cm 3 . The value that appears in the literature is 0.655 g/cm 3 . Calculate the percent error.

5. In an experiment, a student measured the amount of vitamin C in 200 mL of orange juice as 95 mg. The label on the carton stated the amount was 95 mg. What was the percent error in the measurement by the student?

Solve the following density problems.

6. A 16.1 g sample of platinum has a volume of 0.750 cm 3 . What is its density?

7. What volume will 6.38 g of the mineral quartz occupy, given that its density is 2.65 g/cm 3 ?

8. If the density of silver is 10.5 g/cm 3 , what is the mass of a sample of silver that occupies 65 cm 3 ?

9. Calculate the mass, in kilograms, of an object that occupies 15.3 cm3 and that has a density of 4.14 g/cm3.

10. What volume will 41.2 g of carbon tetrachloride occupy, if it has a density of 1.90 g/ cm 3 ?

Accuracy and Precision

11. Each of five students used the same ruler to measure the length of the same pencil. The measurements gave these results: 15.33 cm, 15.34 cm, 15.33 cm, 15.33 cm, 15.34 cm. The actual length of the pencil was 15.55 cm. Using these numbers as examples, distinguish between accuracy and precision.

12.Comment on the accuracy and precision of these basketball freethrow shooters. a. 99 of 100 shots are made. b. 99 of 100 shots hit the front of the rim and bounce off. c. 33 of 100 shots are made; the rest either miss the rim completely or rebound off the

backboard.

Chem Mystery 14

13.Three students made multiple masses of a copper cylinder, each using a different balance. The correct mass of the cylinder had been previously determined to be 47.432 g. Describe the accuracy and precision of each student’s measurements.

Mass of Cylinder

Jim Ann Randall

Mass #1 47.13 g 47.45 g 47.95 g Mass #2 47.94 g 47.39 g 47.91 g Mass #3 46.83 g 47.42 g 47.89 g Mass #4 47.47 g 47.41 g 47.93 g

Significant Figures

14. Accurately read the following values. Be sure to record the correct number of decimal places (significant figures) and the units that the measurement is in.

15. Draw the gradations on three graduated cylinders which produced the following measurements 24.6 mL 43 mL 9.34 mL

Units

Match the prefixes, with their equivalent values. Identify the kind of quantity measured Write the letter of the correct value in the blank by each unit. provided.

a. Thousand ____ 16. centi 22. Meter ______________ b. Ten ____ 17. kilo 23. Milliliter ______________ c. Tenth ____ 18. deci 24. Kelvin ______________ d. Hundredth ____ 19. milli 25. Gram ______________ e. Thousandth ____ 20. micro 26. Cm 3 ______________ f. Millionth ____ 21. deca g. Billionth

27. An object is 1.3 m long, 0.65 m wide, and 15 cm high. Calculate the volume of this object.

28. A desktop is found to be 1.26 m long and 0.85 m wide. Calculate its area.

1 2 3 4 cm

1 2 3 4 cm

5 6 7 8

Chem Mystery 15

29. Two samples of the same liquid are mixed together. If the total volume is 95.3 cm 3 , and the volume of one of the liquids alone was 17.624 cm 3 , what was the volume of the other liquid?

30. The mass of a beaker is found to be 40.2 g. The mass of the beaker plus a substance placed into it is 63.16 g. Calculate the mass of the substance.

31. The volume of a large desk drawer is 0.31 m 3 . How high is the drawer if it is 0.94 m long and 0.579 m wide?

Change the following metric measurements into the units asked for.

32. Calculate the number of millimeters there are in 0.31 kilometers.

33. The distance between two atoms is 0.0000000011 m. What is this distance in cm?

34. How many millimeters are there in 22.35 cm?

35. Calculate the number of mL in 3.5 L.

36. A balloon has a volume of 10 L. What is its volume in cubic centimeters?

The table below shows the masses and volumes of nine different samples of the same substance.

Mass (g) Volume (cm 3 ) Mass (g) Volume (cm 3 ) 0.50 0.71 6.5 9.3 2.0 2.9 7.0 10.0 3.5 5.0 8.5 12.1 4.5 6.4 10.0 14.3 5.0 7.1

37. Calculate the density of each of nine samples, to the appropriate number of significant figures. 38. Plot the mass and volume data, to create a graph of mass (yaxis) versus volume (xaxis).

Calculate the slope of the graph (change in y to change in x).

Graph:

Title

Chem Mystery 16

39. How does the value of the slope relate to that of the densities you calculated earlier?

40. Using the density from question 37, calculate the mass of a sample of the substance that occupies 3.0 cm 3 .

41. Using the density from question 37, calculate the volume of a sample of the substance that has a mass of 45 g.

42. Four balloons filled with neon, carbon dioxide, nitrogen, and hydrogen are released into the air. Using the data below, describe the movement of each balloon. (Up/Float or Down/Sink)

Substance Density at 20 o C (g/L) Air 1.20 Carbon Dioxide 1.83 Hydrogen .084 Neon .84 Nitrogen 1.19

Experimental Design Boxes

43. A student wanted to answer the question, “How does temperature affect the rate of an enzyme reaction?”. She decided to test the temperatures of 10 o C, 20 o C, and 50 o C. She would add 10 mL of enzyme to 50 mL of reactants. She measured the time it takes for the bubbling reaction to stop. Complete an experimental design table about the above experiment.

44. What problem did the student investigate? 45. What might have been one hypothesis she made?

46. Another student did an experiment to discover which acid would react fastest with magnesium. He put a 1 gram piece of magnesium into 100 mL of each acid. He would measure the time for the reaction to cause the piece of magnesium to disappear. He tried the following acids: 1M HCl, 1M H2SO4, 1M HNO3, and 1M HC2H3O2 . Complete an experimental design table for his experiment.

chem mystery - behs science · chem mystery 11 student number ... read pages 56 through 60 in...

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