Packet 1 - Holy Family Catholic Schools

Chemistry
Name:__________________
Period:____
Introduction to Chemistry
Packet 1
Day
In Class Work
1 Scientific Method/ Bubble Lab
2 Variables and Constants
3 Variable Lab
4 Candle Lab
5 Using a Banlance
6 Sodium Bicarbonate Lab
7 Packet Test
Outcomes
‣ Students will explain and apply the scientific method.
‣ Students will be able to read the mass setting on the balance.
‣ Students will correctly determine the mass of objects to the hundredth.
Chemistry: The study of change
1

The Scientific Method
A Nobel Prize winner in science once said that science is about “ordinary people doing ordinary
things.” Scientists have a powerful tool that they can use to produce valuable, sometimes
spectacular, results. Like all scientists, the biochemist shown in Figure 1.18 is using the scientific
method to solve difficult problems. The scientific method is a logical, systematic approach to the
solution of a scientific problem. Steps in the scientific method include making observations,
testing hypotheses, and developing theories.
Making Observations
The scientific method is useful for solving many kinds of problems because it is closely related to
ordinary common sense. Suppose you try to turn on a flashlight and you notice that it does not
light. When you use your senses to obtain information, you make an observation. An observation
can lead to a question: What’s wrong with the flashlight?
Testing Hypotheses
If you guess that the batteries are dead, you are making a hypothesis. A hypothesis is a proposed
explanation for an observation. You can test your hypothesis by putting new batteries in the
flashlight. If the flashlight lights, you can be fairly certain that your hypothesis is true. What if the
flashlight does not work after you replace the batteries? A hypothesis is useful only if it accounts for
what is actually observed. When experimental data does not fit a hypothesis, the hypothesis must be
changed. A new hypothesis might be that the light bulb is burnt out. You can replace the bulb to test
this hypothesis.
Replacing the bulb is an experiment, a procedure that is used to test a hypothesis. When you design
experiments, you deal with variables, or factors that can change. The variable that you change
during an experiment is the manipulated variable, or independent variable. The variable that is
observed during the experiment is the responding variable, or dependent variable. If you keep
other factors that can affect the experiment from changing during the experiment, you can relate any
change in the responding variable to changes in the manipulated variable.
For the results of an experiment to be accepted, the experiment must produce the same result no
matter how many times it is repeated, or by whom. This is why scientists are expected to publish a
description of their procedures along with their results.
Word Origins
Experiment contains the Latin root peri, meaning “to try or test.” The words expert and
experience contain the same root. How could experiments provide the experience for someone
to become an expert.
2

Bubbles!
Purpose
To test the hypothesis that bubble making can be affected by adding sugar or salt to a bubbleblowing
mixture.
Materials
3 plastic drinking cups
drinking straw
pre-mix bubble solution
Procedure
1. Label three microbeakers1, 2, and 3. Fill each beaker
½ full with bubble solution.
2. Dip the drinking straw into cup 1, remove it, and blow
gently into the straw to make the largest bubble you
can. Practice making bubbles until you feel you have
reasonable control over your bubble production.
3. Repeat Step 3 with the mixtures in cups 2 and 3.
Analyze and Conclude
1. Did you observe any differences in your ability to produce bubbles using the mixtures in
cup 1 and cup 2?
2. Did you observe any differences in your ability to produce bubbles using the mixtures in
cup 1 and cup 3?
3. What can you conclude about the effects of table sugar and table salt on your ability to
produce bubbles?
4. Propose another hypothesis related to bubble making and design an experiment to test
your hypothesis.
5. Why are bubbles round?
3

Developing Theories
Once a hypothesis meets the test of repeated experimentation, it may be raised to a higher level of
ideas. It may become a theory. A theory is a well-tested explanation for a broad set of observations.
In chemistry, one theory addresses the fundamental structure of matter. This theory is very useful
because it helps you form mental pictures of objects that you cannot see. Other theories allow you
to predict the behavior of matter.
When scientists say that a theory can never be proved, they are not saying that a theory is
unreliable. They are simply leaving open the possibility that a theory may need to be changed at
some point in the future to explain new observations or experimental results.
Scientific Laws
A scientific law is a concise statement that summarizes the results of many observations and
experiments. In Chapter 14, you will study laws that describe how gases behave. One law describes
the relationship between the volume of a gas in a container and its temperature. If all other variables
are kept constant, the volume of the gas increases as the temperature increases. The law doesn’t try
to explain the relationship it describes. That explanation requires a theory.
Independent & Dependent Variables
Independent Variables (IV) & Dependent Variables (DV)
In an experiment, the independent variable is the variable that is varied or
manipulated by the researcher, and the dependent variable is the response that is
measured.
An independent variable is the presumed cause, whereas the dependent variable is the presumed
effect. ***The IV is the antecedent, whereas the DV is the consequent.
In experiments, the IV is the variable that is controlled and manipulated by the experimenter;
whereas the DV is not manipulated, instead the DV is observed or measured for variation as a
presumed result of the variation in the IV.
When reseaerchers are not able to actually control and manipulate an IV, it is technically referred to
as a status variable (e.g., gender, ethnicity, etc.). Even though researchers do not actually control or
manipulate status variables, researchers can, and often do, treatthem as IVs (Heppner, Kivlighan &
Wampold, 1999).
"The DV refers to the status of the 'effect'(or outcome) in which the researcher is interested; the
independent variable refers to the status of the presumed 'cause,' changes in which lead to changes
in the status of the dependent variable…any event or condition can be conceptualized as either an
independent or a dependent variable. For example, it has been observed that rumor-mongering can
sometimes cause a riot to erupt, but it has also been observed that riots can cause rumors to surface.
4

Rumors are variables that can be conceived of as causes (IVs) and as effects (DVs)." (Rosenthal &
Rosnow, 1991, p. 71)
Some Examples of Independent and Dependent Variables
1. "There will be a statistically significant difference in graduation rates of at-risk high-school
seniors who participate in an intensive study program as opposed to at-risk high-school seniors who
do not participate in the intensive study program." (LaFountain & Bartos, 2002, p. 57)
IV: Participation in intensive study program. DV: Graduation rates.
List the Independent and Dependent Variables for the following:
If one were to measure the influence of different quantities of fertilizer on plant growth, the
independent variable would be the __________________ used (the changing factor of the
experiment). The dependent variables would be the ________________ of the plant (the factors
that are influenced in the experiment) and the controlled variables would be the
_____________________________________________________________________________
_____________________________________________________________________________
In a study of how different doses of a drug affect the severity of symptoms, a researcher could
compare the frequency and intensity of symptoms (_______________ variables) when different
doses (_______________ variable) are administered, and attempt to draw a conclusion. The
controlled variables would be the
_____________________________________________________________________________
In measuring the acceleration of a vehicle, time is usually the ___________ variable and speed
is the ____________ variable. This is because when taking measurements, times are usually
predetermined, and the resulting speed of the vehicle is recorded at those times. The controlled
variables would be the
_____________________________________________________________________________
In measuring the amount of color removed from beetroot samples at different temperatures, the
dependent variable would be the_________________, because it is depending on the
_______________ (which is the independent variable). The controlled variables would be the
_____________________________________________________________________________
In sociology, in measuring the effect of education on income or wealth, the dependent variable
could be a _____________________ measured in monetary units (United States Dollars for
example), and an independent variable could be the ________________of the individual(s) who
compose(s) the household (i.e. academic degrees). The controlled variables would be the
_____________________________________________________________________________
5

Variables and Constants
Many experiments are designed to determine the relationship between the independent and
dependent variable. The other variables which could interfere with the experiment must be held
constant.
In this experiment we will investigate if the time need to heat water to 80° C is affected by its
distance from Bunsen burner. The independent variable is ____________________________ and
the dependent variable is _____________________________.
In order to find the relationship between these two variables, other variables which could interfere
with the investigation must be held constant. Some possible constants for this experiment are
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Write a procedure to solve the problem we are investigating. A procedure is a series of steps to
follow to perform the lab. These steps are written to control each of the constants. Each numbered
step should contain only one idea.
Procedure
Data:
Conclusion:
How could this lab be improved?
6

Candle Lab
Problem: What products form in the chemical reaction of a burning-candle?
Make observations about candles?
Hypothesis-
Experiment
1. Place a drop of tap water on a piece of cobalt chloride test paper, and indicator, and note the color change
caused by water. What does cobalt chloride paper indicate? _________________
2. Light the candle and invert a 400ml beaker over the flame until it goes out. Test any liquid formed in the
beaker with the cobalt chloride test paper.
3. Is this evidence for water being a product and explain.
4. Obtain a 50-ml Erlenmeyer flask and fill it half full with limewater, an indicator. The lime water is
dispensed by gravity so just pinch the stopcock.
5. Measure 10 ml of lime water into the flask. Exhale through a straw into the lime water until a change
occurs. What does limewater indicate? ____________
6. Obtain a 50-ml Erlenmeyer flask, relight the candle, and invert the flask over the burning candle until the
flame goes out. Remove the flask and quickly place it upright. Add about 10 ml of limewater solution to the
flask, seal it a glass plate, swirl the solution, and watch for changes in the solution. Carbon dioxide gas
causes limewater to turn cloudy.
7. Decide if this is evidence for carbon dioxide being a product and explain.
8. Make a data table with two columns, one for time and one for temperature.
9. Obtain a large test tube, test tube holder and thermometer. Half fill the test tube with tap water. Measure
and record the temperature of the water; record this first time entry as zero. Keep the thermometer in the
middle of the water and away from the sides and bottom of the test tube. Hold the test tube just above the
candle flame, heat the water and record the temperature every 30 seconds for two minutes. This will give
you five temperatures to record.
7

10. Plot a temperature-time graph with time as the independent variable and temperature as the dependent
variable.
11. Decide if heat is a product and explain.
12. Write a conclusion.
8

Scientific Method
A marine biologist conducted a study of the ability of vertebrate blood to carry oxygen. He believed that a low
environmental temperature would cause the organism's blood to carry less oxygen than blood at a higher
temperature. The following reflects the scientists experiment and the data he collected.
Two tanks of salt water, each containing 25 gallons, was set up in the lab.
Each tank was filled with the same types of organisms ( perch and salmon ).
The same type of aerators were added to each tank to supply dissolved oxygen to the fish.
To one of the tanks, marked TANK A, the temperature was decreased at increments of 5 degrees C
every 20 minutes.
The second tank, marked TANK B, the temperature is raised at increments of 5 degrees C every 20
minutes.
Blood was removed from each of the fish and measured for its oxygen content.
Below is the results from the above experiment.
Temperature in
Degrees C
Amount of Dissolved Oxygen
found in fish in Tank A -ml/g
Temperature in
Degrees C
Amount of Dissolved Oxygen
found in fish in Tank B -ml/g
25 35 25 35
20 30 30 32
15 23 35 39
10 12 40 35
5 8 45 20
1. What is the hypothesis of the above experiment?
_____________________________________________________________________________
2. Is the above experiment a controlled experiment?
_____________________________________________________________________________
3. Explain your answer to question 2.
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
4. What term would be used to denote a person who studies blood?
_____________________________________________________________________________
5. What is the variable factor in the above experiment?
_____________________________________________________________________________
9

Line Graph the above data and then answer the questions that follow.
TITLE: _____________________________________________________________________
6. What is the dependent variable?
____________________________________________________________________________
7. What is the independent variable?
____________________________________________________________________________
8. Based on the above data, is the scientists hypothesis correct?
____________________________________________________________________________
9. What are the controls used in the above
experiment?__________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
10

Packet 1 Scientific Method
1. Why should a hypothesis be developed before experiments take place?
2. Why is it important for scientists to publish a description of their procedures along with the
results of their experiments?
3. What is the difference between a theory and a scientific law?
4. If your heart beats at an average rate of 72 times per minute, how many times will your heart
beat in an hour? In a day?
5. How many days would it take you to count a million pennies if you could count one penny each
second?
6. Describe a situation in which you used at least two steps in the scientific method to
solve a problem.
7. Pure water freezes at 0°C. A student wanted to test the effect of adding salt to the water. The
table shows the data that was collected.
a. What was the manipulated/independent
variable?
b. What was the responding/dependent
variable?
c. Why must the volume of water be the
same for each test?
d. Based on the data, the student hypothesized, “As more salt is added to water, the
temperature of the water decreases.” Is this hypothesis supported by the data? Explain.
Use this paragraph to answer Questions 8–10.
(1) On a cold morning, your car does not start. (2) You say, “Oh no! The battery is dead!”. (3) Your
friend who works on cars uses a battery tester and finds that the battery has a full charge. (4) Your
friend notices a lot of corrosion on the battery terminals. (5) Your friend says, “Maybe corrosion is
causing a bad connection in the electrical circuit, preventing the car from starting.” (6) Your friend
cleans the terminals and the car starts.
8. Which statements are observations?
9. Which statements are hypotheses?
10. Which statement describes an experiment?
11