Chemistry I Summative 1 Study Guide

Completion

Complete each statement.

1.The extent to which a measurement approaches the true value is referred to as ______.

2.______is the closeness of a measurement to the actual value being measured.

USING SCIENCE SKILLS

Figure 1-2

3.Controlling VariablesIn Figure 1-2, what is the responding variable?

USING SCIENCE SKILLS

A scientist conducted an experiment to determine the effect of environment on the color of fur of a Himalayan rabbit. The Himalayan rabbit typically has a white coat except for its colder nose, feet, tail, and ears, which are black. The scientist shaved an area of hair on the back of each rabbit, then placed an ice pack over the shaved area on one rabbit (A).

Figure 1–1

4.Interpreting Graphics In Figure 1–1, which rabbit is the control?

5.Applying Concepts Why is Rabbit B essential to this experiment?

6.Interpreting Graphics In Figure 1–1, what is the variable in this experiment?

7.Formulating Hypotheses Before completing the experiment in Figure 1–1, the scientist made a hypothesis. What is the hypothesis she is testing?

8.Drawing Conclusions Based on your observations of Figure 1–1, conclude what effect temperature has on Himalayan rabbits.

9.An organized plan for gathering, organizing, and communicating information is called a(an) ______.

10.Although a measurement of 6.13457902 cm is very ______, it may not be accurate.

Figure 1-3

11.InferringWhy might the data in Figure 1-3 be important to share with a scientist studying agriculture in Port Hardy?

12.A(An) ______explains a pattern found in nature.

13.An experiment in which only one variable, the manipulated variable, is changed at a time is called a(an) ______.

14.Any factor in an experiment that can change is referred to as a(n) ______.

15.Each of four students separately makes four measurements of the mass of the same object. The readings are as follows:

Student 1: 9.1 g, 9.2 g, 9.1 g, 9.1 g

Student 2: 11 g, 9 g, 9 g, 11 g

Student 3: 14.1 g, 11.0 g, 17.4 g, 18.8 g

Student 4: 10.1 g, 9.9 g, 10.0 g, 10.0 g.

The real value of the object's mass is 10.0 g. Evaluate each student's set of readings in terms of precision and accuracy.

17.A student measures the mass of an object as 135.80 g. Calculate the percent error in the measurement, given that the accepted value for the mass is 137.23 g.

18.Suppose researchers at a drug company have developed a new medicine that they hope will be useful against a disease. Explain the steps that the researchers might follow in finding out whether the medicine is effective. Relate each step to a step in the scientific method.

19.State three important laboratory safety rules or procedures and explain why each is important.

20.“That measurement is very precise, but it is still not accurate.” Explain how this statement might be true.

21.While walking outside one night, you notice that moths are staying close to a light. Think about this phenomenon and generate a hypothesis to explain why it occurs. Outline the design of a controlled experiment that would test your hypothesis.

22.Explain what causes uncertainty in measurements and provide an example.

23.Describe a possible order of steps of a scientific method used in an investigation.

24.Compare and contrast precision and accuracy.

25.Find the measured mass of a sample if the accepted value is 20 grams and the percent error is 2 percent.

26.Explain the differences between qualitative and quantitative observations.

27.Define the terms theory and hypothesis in a way that shows the role of each in the scientific method.

28.What is an inference?

29.A number of rats are divided into two groups: One group is fed a normal diet, whereas the other group is fed the same diet but with one necessary mineral left out. The animals receiving the normal diet remained healthy; those in the other group grew weaker. Formulate a hypothesis based on this experiment.

30.The following length measurements were taken by students using several different measuring devices. Find the average of the measurements. Was the student accurate or precise? The known value of the item is 12.00 cm.

10.05 cm, 10.1 cm, 9.741 cm, 10.6 cm, 10.5 cm

Chemistry I Summative 1 Study Guide

COMPLETION

1.ANS:accuracy

PTS:1DIF:1REF:3OBJ:3

2.ANS:Accuracy

PTS:1DIF:L1OBJ:1.3.3BLM:knowledge

3.ANS:mass

PTS:1DIF:L2OBJ:1.4.2BLM:comprehension

4.ANS:Rabbit B is the control.

PTS:1DIF:L3REF:p. 9OBJ:1.2.1

NAT:II | A.1 | G.3KEY:evaluation

5.ANS:Rabbit B is the control. An experiment without a control has no value, because the cause of any observed change cannot be determined.

PTS:1DIF:L3REF:p. 9OBJ:1.2.1

NAT:II | A.1 | G.3KEY:evaluation

6.ANS:Ice (temperature) is the variable.

PTS:1DIF:L3REF:p. 9OBJ:1.2.1

NAT:II | A.1 | G.3KEY:analysis

7.ANS:The fur color of the Himalayan rabbit changes with the temperature.

PTS:1DIF:L3REF:p. 8OBJ:1.2.1

NAT:II | A.1 | G.3KEY:synthesis

8.ANS:When the body of a Himalayan rabbit is cool, the rabbit’s hair will grow in dark. When the rabbit’s body is warm, the hair color is the normal white color.

PTS:1DIF:L3REF:p. 10OBJ:1.2.1

NAT:II | A.1 | G.3KEY:synthesis

9.ANS:scientific method

PTS:1DIF:L1OBJ:1.2.1STA:SC-CC-2.1

BLM:knowledge

10.ANS:precise

PTS:1DIF:1REF:3OBJ:3

11.ANS:The precipitation data might provide insight into agriculture.

PTS:1DIF:L2OBJ:1.4.3BLM:comprehension

12.ANS:

scientific theory or

theory

PTS:1DIF:L1OBJ:1.2.2BLM:knowledge

13.ANS:controlled experiment

PTS:1DIF:L1OBJ:1.2.1STA:SC-CC-2.1

BLM:knowledge

14.ANS:variable

PTS:1DIF:1REF:2OBJ:1

ESSAY

15.ANS:

Student 1's results cluster together closely, so they have relatively high precision. However, they are not clustered about the correct value, 10.0, but are significantly off, so they are relatively inaccurate. Student 2's results do not cluster together closely, so they are imprecise. However, they are averaged around the correct value, 10.0, so as a set of data they are fairly accurate. Student 3's results are far apart and are far off the correct value, even when averaged, so they are both imprecise and inaccurate. Student 4's results cluster together closely and are close to the correct value, so they are both precise and accurate.

PTS:1OBJ:1A 1.f

16.ANS:

A theory can change over time. No theory is considered absolute truth. As new evidence is uncovered, a theory may be revised or replaced by a more useful explanation.

PTS:1DIF:L2REF:p. 15OBJ:1.2.2

NAT:A.1 | A.2 | G.2 | G.3KEY:analysis

17.ANS:

PTS:1OBJ:1A 1.h

18.ANS:

Accept all logical answers. A typical correct answer might refer to the following steps: noting a need for the particular medicine and studying the characteristics of a certain disease (observation); asking whether a certain medicine that has been developed will be effective (posing a question); posing the tentative answer that the medicine will be effective (hypothesizing); testing various subjects with the medicine (experimenting); studying the results and deciding whether or not the medicine has proven effective (stating a conclusion); proposing an explanation for why the particular medicine is effective or ineffective (theorizing).

PTS:1OBJ:1A 1.b

19.ANS:

Accept all logical answers. A correct answer might list the following: follow the teacher's directions (not paying attention could lead to dangerous errors in procedure); wear safety goggles (not doing so could result in exposure of eyes to splashes from dangerous substances); tie back long hair (to avoid catching it on fire); let heated objects cool before handling (not to do so could result in burns). Accept other appropriate responses as well.

PTS:1OBJ:1A 1.c

20.ANS:

Answers may vary. Sample answer: Suppose you were measuring a room. You might measure the length at 3.452389 m. This is a very precise measurement. However, if you wrote down the numbers incorrectly, and the actual length was 4.452389, your measurement would not be accurate

PTS:1DIF:2REF:3OBJ:3

21.ANS:

Hypothesis: The moths are attracted to the light and/or heat. One way to test this hypothesis is to set up two identical light bulbs. Turn one bulb on and keep the other off to determine whether only the lit bulb attracts the moths.

PTS:1DIF:L3REF:p. 8 | p. 9OBJ:1.2.1

NAT:II | A.1 | G.3KEY:synthesis

22.ANS:

Uncertainty in measurements occurs because measuring instruments are never completely free of flaws and measuring always involves some estimation. An example that might be cited is a measurement of volume using a graduated cylinder. The cylinder cannot be made without imperfections, so there is a built-in uncertainty connected with its use. Also, in reading the level against the calibrations on the device, the measurer must estimate where the level is located and the number of decimal places to which it may be reported.

PTS:1OBJ:1A 1.e

23.ANS:

Possible answer: (1) make observations, (2) ask questions, (3) develop a hypothesis, (4) test the hypothesis, (5) analyze data, (6) draw conclusions, and (7) revise hypothesis.

PTS:1DIF:L2OBJ:1.2.1STA:SC-CC-2.1

BLM:comprehension

24.ANS:

Precision and accuracy are both evaluations of the reliability of measured values. Precision refers to repeatability of values, or closeness compared to one another. Accuracy refers to the closeness of values to the correct or standard value.

PTS:1OBJ:1A 1.f

25.ANS:

PTS:1OBJ:1A 1.h

26.ANS:

In qualitative observations, the data are descriptive and non-numerical. In quantitative observations, the data are numerical.

PTS:1DIF:IIREF:1OBJ:2

27.ANS:

A theory is a broad generalization based on observations, reasoning, and data that are used to explain a phenomenon and predict future events. A hypothesis is an educated assumption based on observations that can be tested experimentally. When tested, a hypothesis may become a theory.

PTS:1DIF:IIREF:1OBJ:3

28.ANS:

An inference is a logical interpretation based on prior knowledge and experience.

PTS:1DIF:L2REF:p. 4OBJ:1.1.1

NAT:A.1 | A.2 | G.2KEY:comprehension

29.ANS:

Sample answer: The missing mineral in the diet is needed for the health of the rats.

PTS:1DIF:L3REF:p. 5OBJ:1.1.2

NAT:II | A.1 | A.2KEY:synthesis

30.ANS:

Average = (10.05 + 10.1 + 9.741 + 10.6 + 10.5) / 5 = 10.2 cm

Measurements are neither accurate nor precise.

PTS:1DIF:L2REF:p. 68 | p. 71OBJ:3.1.3