Download HOW DO SCIENTISTS APPROACH PROBLEMS

UNIT 1
SOLVING PROBLEMS USING A SCIENTIFIC APPROACH (pp. 8 – 14)
Scientific Method
1. Since any number of scientists around the world can choose to investigate a problem, it would be helpful if
they all used common procedures.
2. The way scientists carry out experiments or investigations is referred to as the ____________________.
3. The scientific method is a logical approach to exploring a problem or question that has been raised through
observation.
4. This approach is designed to produce a solution or answer that can be tested, retested, and supported by
experimentation.
5. The fundamental activities of the scientific method are:
-
Make observations and collect data that can lead to a question. Define the problem. Is it
_______________ or _______________ ?
-
Formulate and objectively test hypotheses by experiments.
-
Interpret results and revise the hypothesis if necessary.
-
State conclusions in a form that can be evaluated by others.
Variables
1. In order to write a good hypothesis to test we need to understand the variables involved.
2. Variables are factors, conditions, and/or relationships that can change or be changed in the experiment.
3. In a scientific investigation there are four kinds of variables:
- The ____________________ variable is a factor or condition that is intentionally changed during the
experiment.
- The ____________________ variable is a factor or condition that might be affected as a result of that change.
- A ____________________ variable is a factor or condition that is not changed.
- A ____________________ is a standard used for comparison.
***** List the variable for the following problem and identify both the independent and dependent variables.
PROBLEM: Determine the % water in a chemical compound
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Hypothesis
1. A __________________ is a proposition based on certain assumptions that can be evaluated scientifically.
2. It is usually written in the form of an ____________________ statement.
3. Steps for writing a good hypothesis:
- Identify variables in a given event or relationship.
- Identify a pair of variables that might logically be related.
- Identify the independent and dependent variable.
- Write the hypothesis.
***** Write a hypothesis for our problem:
Independent variable:
Dependent variable:
Hypothesis:
Experiment
1. An ____________________ is a process carried out under controlled conditions to test the validity of a
hypothesis.
2. By carefully controlling variables, researchers can identify the dependent variable and its relationship with
the other variables.
3. An experiment plan would include the following:
Theory
1. Any conclusion scientists make must come directly and solely from the data they obtain in their experiment.
The data and results may, or may not, support their hypothesis.
2.
Any hypothesis that withstands repeated testing may become part of a _______________.
3.
A theory is an explanation of an observation that is based on experimentation and reasoning.
4.
A theory is not a fact; it is an explanation. Theories can be adjusted as new information comes to light.
Laws
1.
Certain facts in science always hold true. Such facts are labeled as ____________________.
2.
A scientific law is a statement or mathematical expression describing the behavior of the natural world.
3.
There are a limited number of laws in science compared to the number of theories or hypotheses.
4.
A hypothesis __________ an event; a theory __________ it; and a law __________ it.
HOW SHOULD DATA BE REPORTED? (pp. 113 – 130)
Significant Figures and Standard Units
1. Observations and properties can be described most exactly in numerical terms. You can describe a person’s
characteristics such as height, mass or age using words such as:
2. These descriptions are very subjective and vague. Numbers are more useful and make the descriptions more
exact.
3. In this section we will study how data should be reported in terms of significant figures and standard units.
Significant Figures
1. If a measurement is reported with either too many or too few digits, it is not possible to tell how precise the
measurement really is. To indicate precision, significant figures are used.
2. Significant figures are those digits in a measurement that have actually been measured by comparison with a
scale, plus one estimated digit.
3. The number of significant figures you obtain is limited by how finely divided your measuring scale is.
Rules for Significant Figures
1. All nonzero digits are significant. Examples:
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2. All zeros that fall between nonzero digits are significant. Examples:
3. Zeros to the left of the first nonzero digit (leading zeros) in a number are __________ significant; they
merely help indicate the position of the decimal point. Examples:
4. When a number ends in zeros (trailing zeros) that are to the right of a decimal point, they __________
significant. Examples:
5. When a number ends in zeros that are not to the right of a decimal point, the zeros may or may not be
significant. They are not normally considered significant. Examples:
6. Exact numbers. Often calculations involve numbers that were not obtained by using measuring devices but
were determined by counting such as __________ or __________. Such numbers are called exact numbers.
They can be assumed to have an unlimited number of significant figures.
7. Exact numbers can also arise from definitions. For example, 1-inch = 2.54 centimeters. Neither 2.54 nor 1
will have any effect on limiting the number of significant figures when used in a calculation.
8. The rules for significant figures also apply to numbers written in scientific notation:
9. In paragraph 5 it is hard to tell whether zeros to the right of a nonzero digit, but not to the right of a decimal
point, are significant. There are two ways you can write such numbers so you can tell whether such zeros are
significant:
- place a decimal point after the zeros that are significant
- use scientific notation
***** Determine the number of significant figures in each of the following:
503
635.526
500.
630
0.00015
10,001
2.407
601
Rounding Numbers
1. Before we can apply the rules for significant figures to calculations, we need to look at the procedures for
rounding numbers.
2. If the digit to be removed is 5 or greater, the preceding number is _______________ by one.
3. If the digit to be removed is less than 5, then the preceding number is _______________________.
***** Round each of the following measurements to three significant figures:
24.590
3.002
24.353
956.789
OVER
67.963
NAME:
PERIOD:
HOMEWORK 1.1 (2013-2014)
Scientific Method
a. Read pp. 8 - 14
b. Review your notes
c. Answer the following questions:
1. List the parts necessary to create a good hypothesis.
2. Classify each of the following as observation, hypothesis, theory, or law:
a. Mass is neither created nor destroyed during a chemical reaction; it is conserved.
b. The substance is silvery white, fairly hard and is a good conductor of electricity.
c. Collisions between gas particles are perfectly elastic because the particles have no volume and are neither
attracted nor repelled.
d. If I pay attention in class, then I will succeed in this course.
3. A researcher wishes to measure the gas mileage of the Jeep Cherokee. List five variables that can affect the
mileage.
4. Identify the independent, dependent and at least five constants in the following experiment: An experiment is
designed to determine how the brand of coffee affects the percent of caffeine in coffee.
5. You read in the paper that experiments have shown that listening to music increases the efficiency of studying.
Should you immediately start listening to music as you study? Explain.
6. You are asked to study the effect of temperature on the volume of a balloon. Identify the independent and
dependent variables. List two variables that should be held constant. State the hypothesis.
NAME:
PERIOD:
HOMEWORK 1.2 (2013-2014)
Significant Figures – Rounding
a. Review pp 113 – 116; pp 122 - 130.
b. Review your class notes
c. Answer/ solve the following:
1. Determine the number of significant figures in each of the following numbers:
a. 343
e. 0.09305
b. 0.93
f. 10001
c. 340.
g. 3.9 x 103
d. 0.0097
h. 89050
2. Round each of the following numbers to three significant figures:
a. 12.09
e. 23.437
b. 32.647
f. 525.5
c. 0.002017
g. 6.022 x 1023
d. 50.010
h. 3.768 x 10-4
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NAME:
PERIOD:
Unit 1 Review Sheet (2013-2014)
WORD BANK/MULTIPLE CHOICE
experimentation
quantitative data
dependent variable
qualitative data
independent variable
1. Physical characteristics such as color, odor or shape are _________________________.
2. The variable allowed to change or purposely changed by the experimenter is the ____________________.
3. Mass, volume or temperature measurements are called _________________________.
4. The act of gathering information is _________________________.
5. This changes as a result of changing another variable: _________________________.
6. A constant is a factor that
a.
b.
c.
d.
changes during an experiment
changes from one lab group to another
is affected by the dependent variable
is not allowed to change during an experiment
7. A control is a
a.
b.
c.
d.
variable that changes during an experiment
standard for comparison
type of dependent variable
type of experiment
8. A theory is a(n)
a.
b.
c.
d.
set of controlled observations
explanation supported by many experiments
tentative explanation of observations
law describing a relationship in nature
9. The difference between an accepted value and an experimental value is called a(n)
a.
b.
c.
d.
error
percent error
measured value
precise measurement
10. When you calculate percent error, you can ignore the
a.
b.
c.
d.
accepted values
measured values
experimental values
plus and minus signs
11. If two measurements are very close to each other, then they are
a.
b.
c.
d.
accurate
precise
both accurate and precise
accepted values
12. Which of the following is most likely to produce data that are not precise?
a.
b.
c.
d.
a balance that is not set to zero
not reading a graduated cylinder at eye level
altering the procedure during an experiment
making the same error with each trial
SIGNIFICANT FIGURES
13. Determine the number of significant figures in each of the following numbers:
a. 0.125 _____
f. 8627 _____
b. 0.0147 _____
g. 0.1051 _____
c. 600 _____
h. 8000 _____
d. 503.0 _____
i. 404 _____
e. 250,001 _____
j. 0.00078 _____
ROUNDING NUMBERS
14. Round each of the following numbers to four significant figures:
a. 4.34825
_______________
d. 2.79353 x 10-4 _______________
b. 0.068755
_______________
e. 0.00040591
_______________
c. 45.9019
_______________
f. 9073.45
_______________
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