Group Members



Chemistry Name __KEY__________________ Pd.____

Scientific Method Questions 8-28-13

1. A student formulated a hypothesis that cotton will grow larger bolls (pods) if magnesium is added to the soil. The student has two experimental fields of cotton, one with magnesium and one without. Which data should be collected to support this hypothesis?

(a) height of the cotton plants in both fields

(b) diameter of the cotton bolls in both fields

(c) length of the growing season in both fields

(d) color of the cotton bolls in both fields

____B___ Why? The student’s hypothesis said the Mg would make the cotton bolls grow LARGER, so height, and color as well as length of the growing season do not relate to the hypothesis.

2. The current knowledge concerning cells is the result of the investigations and observations of many scientists. The work of these scientists forms a well-accepted body of knowledge about cells. This body of knowledge is an example of a

(a) hypothesis

(b) controlled experiment

(c) theory

(d) research plan

_____C__ Why Because a THEORY is a well-accepted idea based on many experiments performed by many different researchers.

3. In his theory, Lamarck suggested that organisms will develop and pass on to offspring variations that they need in order to survive in a particular environment. In a later theory, Darwin proposed that changing environmental conditions favor certain variations that promote the survival of organisms. Which statement is best illustrated by this information?

(a) Scientific theories that have been changed are the only ones supported by scientists.

(b) All scientific theories are subject to change and improvement.

(c) Most scientific theories are the outcome of a single hypothesis.

(d) Scientific theories are not subject to change.

___B___ Why? Theories are always subject to change or revision as new research data becomes available.

4. A student wanted to test the hypothesis that rooting hormones will stimulate the production of new roots at a faster rate than would take place without rooting hormones. Two stem cuttings of equal length, similar to the one shown below, were taken from a rose, a begonia, and a geranium plant.

[pic]

The cut end of one cutting from each plant was dipped into the hormone and then planted in wet sand. The other cutting from each plant was planted in wet sand without dipping it into the hormone. All cuttings were maintained in identical environmental conditions. At the end of 4 weeks, all the cuttings were removed from the sand and the lengths of the roots that had developed were measured. The results are summarized in the data table below.

[pic]

5. Describe one way the student could make the experiment more valid.

The student should have used MORE THAN ONE SPECIMEN of each plant variety. One subject is not enough to base results upon.

6. What purpose did the untreated cuttings serve in this experiment?

The untreated cuttings serve as the CONTROL GROUP.

7. Acid rain can have a pH between 1.5 and 5.0. The effect of acid rain on the environment depends on the pH of the rain and the characteristics of the environment. It appears that acid rain has a negative effect on plants. The scale below shows the pH of normal rain.

[pic]

Provide the information requested below that should be included in a research plan to test the effect of pH on the early growth of bean plants in the laboratory.

A. State a hypothesis: “Plant growth will be affected when exposed to acid rain.”

“I think plant growth will be affected by acid rain.”

“Plants exposed to acid rain will not grow as well as those

exposed to normal rain”.

B. State a null hypothesis: “Acid rain will have no effect on plant growth.”

C. Identify the independent variable: The acid rain

D. State TWO factors that should be kept constant (there are more than two possible):

Sunlight, temperature, humidity, soil type, fertilizer, bean variety.

E. How would you construct a data …..

|Plant Number |Plant Height, centimeters |

| |Acid Rain |Normal Rain |

|1 | | |

|2 | | |

|3 | | |

|N | | |

11. Many people who are in favor of alternative medicine claim that large doses of vitamin C introduced into a vein speed up the healing of surgical wounds. Describe an experiment to test this hypothesis. Your answer must include at least:

• the difference between the experimental group of subjects and the control group

• two conditions that must be kept constant in both groups

• data that should be collected

• an example of experimental results that would support the hypothesis

The experiment would require TWO groups of subjects: The group that gets the Vitamin C injections would be the EXPERIMENTAL GROUPT while the group that DOES NOT get the Vitamin C injections would serve as the CONTROL GROUP in this experiment.

Each groups should contain subjects of similar size, health status, ethnic group, surgical procedures, diet, medications, (other)…

Wound sizes should be measured at regular intervals, the amount of Vitamin C injected.

If the group of subjects that received the injections healed more quickly than those who did not receive the injections, then the data would seem to support the hypothesis. LARGER trials would need to be conducted in different locations with subjects of varying, health status, ethnicity, etc.

12. A student recorded the following data table for a six month period. She recorded the amount of rainfall that fell per week as measured by the school’s rain gauge.

|Week |Rainfall Amount |Week |Rainfall Amount |Week |Rainfall Amount |

|1 |0.1 inches |9 |0.1 inches |17 |0.1 inches |

|2 |0.3 inches |10 |0.2 inches |18 |0.0 inches |

|3 |0.0 inches |11 |0.1 inches |19 |0.2 inches |

|4 |0.2 inches |12 |0.5 inches |20 |0.2 inches |

|5 |0.0 inches |13 |1.1 inches |21 |0.0 inches |

|6 |0.2 inches |14 |0.7 inches |22 |0.1 inches |

|7 |0.3 inches |15 |0.6 inches |23 |0.3 inches |

|8 |0.0 inches |16 |0.3 inches |24 |0.2 inches |

Make a graph (your choice of type) to display the data.

[pic]

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

A. From your graph what trends or patterns do you see in the rainfall? Overall the rainfall is fairly consistent until weeks 12-16 when it increases significantly, then returns to a similar pattern as in the first weeks.

B. When did the greatest amount of rain fall? Week 13

C. When did the least amount of rain fall? Weeks 3, 5, 8, 18 and 21

-----------------------

1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.0

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download