Chemistry Test 2

Practice 3 (Sample Problem 2-5): Calculate the area of a crystal surface that measures 1.34 µm by (x)0.7488 µm.

1.34 µm x 0.7488 µm = 1.00 µm2 since you would have to round to the least amount of placeholders to the right of the decimal.

Practice 1 (Sample Problem 2-5): What is the sum of 2.099 g and 0.05681?

2.099 g + 0.05681 g = 2.156 g since you would have to round to the least amount of placeholders to the right of the decimal.

Practice problems after the sample problems Practice 1 (Sample Problem 2-3): What is the percent error for a mass measurement of 17.7 g, given that the correct value is 21.2 g?

21.2 g - 17.7 g / 21.2 g X 100 = 17% (two digit sig fig)

Practice 2 (Sample Problem 2-3):A volume is measured experimentally as 4.26 mL. What is the percent error, given that the correct value is 4.15 mL?

4.15 - 4.26 / 4.15 X 100 = -2.7% (two digit sig fig)

Practice 2 (Sample Problem 2-5): Calculate the quantity 87.3 cm - 1.655 cm.

87.3 cm - 1.655 cm = 85.6 cm since you would have to round to the least amount of placeholders to the right of the decimal.

What is accuracy? A. It is the closeness of measurements to the correct or accepted value of the quantity measured. B. It is the closeness of a set of measurements of the same quantity made in the same way. C. Both D. None of the Above

A

What is an hypothesis? A. an educated guess that you can test B. the main idea in a document C. the next step after a thesis statement D. none of the above

A

What is scientific notation? A. In scientific notation, numbers are written in the form M x 10^n, where the factor M is a number greater than or equal to 1 but less than 10 and n is a whole number. B. In scientific notation, numbers are written in the form M x 10^n, where the factor M is a number greater than or equal to 10 but less than 100 and n is a whole number. C. In scientific notation, numbers are written in the form M x 10^n, where the factor M is a number greater than or equal to 1 but less than 10 and n is a natural number. D. none of the above

A

What is a control and what might be functioning as a control for this experiment?

A control is used as the standard for comparison. For example, if you give a plant no fertilizer, then you would not expect special growth. The yellow line could represent a control.

How do hypotheses and theories differ?

A hypothesis is a testable statement that serves as a basis for making predictions and for carrying out further experiments. A theory is a broad generalization that explains a body of facts or phenomena.

What is a system?

A system is a specific portion of matter in a given region of space that has been selected for study during an experiment or observation.

How are models related to theories and hypotheses?

A useful model is usually proposed after a hypothesis is shown to be correct. A model that successfully explains many phenomena may become part of a theory.

Practice 1 (Sample Problem 2-4): How many significant figures are in? A. 804.05 g. B. 0.014 403 0 km. C. 1002 m. D. 400 mL. E. 30 000 cm. F. 0.000 625 000 kg.

A. 5 B. 6 C. 4 D. 1 E. 5 F. 6

Practice 2 (Sample Problem 2-4): Suppose the value "seven thousand centimeters" is reported to you. How should the number be expressed if it is intended to contain the following? 1 significant figure 4 significant figures 6 significant figures

A. 7000 cm B. 70000. cm C. 7000.00 cm

A. What is the density of an 84.7 g sample of an unknown substance if the same occupies 49.6 cm^3? B. What volume would be occupied by 7.75 g of this same substance?

A. The density would be 1.71 g/cm3 because 84.7 g /49.6 cm3 is 1.71 g/cm^3. B. The volume that would be the same as 7.75g would be 4.53 cm^3

What is the volume, in cubic meters, of a rectangular solid that is 0.25 m long, 6.1 m wide, and 4.9 m high?

Answer is 7.5 m^3. The volume would be 7.5 m^3 because 0.25 x 6.1 x 4.9 is 7.5 m^3.

How many significant figure are in the number: 0.046 04 L? A. 0 B. 4 C. 6 D. none of the above

B

What is precision? A. It is the closeness of measurements to the correct or accepted value of the quantity measured. B. It is the closeness of a set of measurements of the same quantity made in the same way. C. Both D. None of the Above

B

How much is 25.1 g + 2.03 g? A. 27.13 g B. 27.00 g C. 27.1 g D. none of the above

C

Which is the correct explanation for finding percent error? A. Subtract the accepted value from the experimental value, dividing the difference by the experimental value, and then multiplying by 100. B. Subtract the accepted value from the experimental value, dividing the difference by the accepted value, and then multiplying by 100. C. Subtract the experimental value from the accepted value, dividing the difference by the accepted value, and then multiplying by 100. D. none of the above

C

Which of the following are quantatives? A. The liquid on water B. The metal is malleable C. The liquid has a temperature of 55.6 degrees C

C

Which represents the definition for significant figures? A. Significant figures in a measurement consist of all the digits known with certainty plus one final digit, which is never estimated. B. Significant figures in a measurement consist of all the digits known with certainty plus one extra digit for added measure.. C. Significant figures in a measurement consist of all the digits known with certainty plus one final digit, which is somewhat uncertain or is estimated. D. none of the above

C

What is the density of the unknown substance using the following figures, 3.05 g / 8.47 mL? A. 0.4 g/mL B. 0.360 094 451 g/mL C. 0.360 09 g/mL D. none of the above

D

Which would NOT have anything to do with the scientific method? A. formulating an hypothesis B. observing and collecting data C. formulating a theory D. none of the above

D

Express the formula for density in a mathematical way.

Density = mass/volume or D = m/v

Is density a physical property?

Density is a physical property in chemistry since it does not depend on the size of the sample. If I had a sink filled with water or just a small glass, the amount of water does not change the density.

What is density?

Density is the ratio of mass to volume, or mass divided by volume.

For figure 2-2, let us pretend that the hypothesis is: There will be no change in plant growth when a plant is exposed to phosphorus fertilizer. Based on the chart, what would you conclude?

I would conclude that the hypothesis was not proven. In fact, based on the data, there was greater growth with plants that had fertilizer.

According to the reading in the text, what is a hypothesis?

It is a testable statement.

Is density a derived SI unit? If so, why?

Length is a base unit in SI (also known as the metric system). Volume is often described as length times width times height Therefore, volume is derived from the base metric measurement of length, which uses meters (m). Density uses volume, which is derived from length, so it is a derived measurement, too. It does not matter that density uses the base measurement of mass, grams (g) since volume is derived and is not a base unit.

Read the caption for figure 2-1. How might you design an experiment that studies some factor and popcorn?

One experiment would be to determine how to get the largest volume of popped corn from a fixed number of kernels.

What is the difference between qualitative and quantitative data?

Qualitative data uses words to describe observations whereas quantitative data uses numbers to describe observations.

Solve practice problem 2 after sample problem 2-1. Diamond has a density of 3.26 g/cm^3. What is the mass of a diamond that has a volume of 0.350 cm^3?

The answer is 1.14 g because 3.36 g/cm^3 multiplied by 0.350 cm^3 is 1.14 g.

Solve practice problem 1 after sample problem 2-1. What is the density of a block of marble that occupies 310cm^3 and has a mass of 853 g?

The answer would be 2.75 g/cm^3 because 853 divided by 310 = 2.75 g/cm^3.

Solve practice problem 3 after sample problem 2-1. What is the volume of a sample of liquid mercury that has a mass of 76.2 g, given that the density of mercury is 13.6 g/mL?

The answer would be 5.60 mL because 76.2 g divided by 13.6 g/mL is 5.60 mL.

Practice 4 (Sample Problem 2-5): Polycarbonate plastics has a density of 1.2 g/cm^3. A photo frame is constructed from two 3.0 mm sheets of polycarbonate. Each sheet measures 28 cm by 22 cm. What is the mass of the photo frame?

The density has a label g/cm3. It would make sense then to keep all measurements in cm as you calculate. Therefore, the initial depth of the two sheets is 0.6 cm versus 6 mm, since we want this depth to use a similar label as the goal density label. Now multiply 0.6 cm times 28 cm times 22 cm, giving us a volume of 369.6 cm3. Density = mass/volume, so density times volume will equal the mass. 1.2 g/cm3 x 369.6 cm3 equals 443.52 g, however, it is 440 g since the initial density number is limited to two significant figures. This would mean that our answer, the product, must only be expressed with two significant figures.

Find the density of a material, given that a 5.03 g sample occupies 3.24 mL. (Hint: See Sample Problem 2-1.)

The density of the material would be 1.55 g/mL because 5.03 g/ 3.24 mL is 1.55 g/mL.

Which colored line shows the most growth over time? Why do you think that this is the case, using data related to the growth to support your conclusion?

The red and blue lines both show the best growth over time. Over a period of around twenty days, the two lines showed a total growth of about 25 cm. These solutions possessed greater concentrations of phosphorus fertilizer.

What is the scientific method? (section review)

The scientific method is a logical approach to solving problems by observing and collecting data, formulating hypotheses, testing hypotheses, and formulating theories supported by data.

What is the scientific method?

The scientific method is a logical approach to solving problems by observing and collecting data, formulating hypotheses, testing hypotheses, and formulating theories that are supported by data.

According to table 2-4, which substances would float in water? which substances would not float in water?

The substances that float in water are cork, butter, ice, gasoline, ethyl alcohol, kerosene, and turpentine. The substances that don't float in water are sucrose, bone, diamond, copper, lead, seawater, milk, and mercury.

For figure 2-2, what does the x axis represent and what does the y axis represent?

The x axis represents time while the y axis represents growth in centimeters (cm).

Which colored line shows the least growth over time? Why do you think that this is the case, using data related to the growth to support your conclusion?

The yellow line shows the least growth over time. At the beginning of the experiment, none of the plants showed growth, however over a period of around twenty days, the yellow line (no fertilizer) showed a total growth of almost 7 centimeters. All the other colored lines (using fertilizer) showed growth.

What are the components of the system in the graduated cylinder shown on page 38?

Water, copper shot, and mercury.