Download Scientific Method

TAKS Objective 1
The Nature of Science:
Safety
Equipment
Measurement
Scientific Method
Safety Rules and
Symbols
Important Safety Terms
• Corrosive- Will corrode or eat away metal, skin,
or other substances. (acid or base)
• Flammable (may ignite) - will catch on fire or
explode easily
• Volatile- Evaporates quickly, may form
dangerous vapors (vapors may or may not be
flammable)
• Ventilation*- removing contaminated air/vapors
and bringing in fresh air (open windows or a use
fume hood)
*Dangerous vapors may cause
respiratory damage
Safety Rules: The Big Ones
•
General: Tie your hair back & wear closed toe shoes
•
Diluting an Acid: Pour acid into water slowly
(PAWS)
•
Work with volatile chemicals only in a wellventilated area or fume hood to remove vapors.
•
Wear goggles and an apron when working with
chemicals, fire or glassware
•
Wear gloves when working with bacteria, living or
nonliving specimens (treat as a biohazard)
•
Glassware & heat: Don’t heat closed containers
(pressure↑ can cause glassware to explode).
•
Heating: Don’t direct a test tube opening at anyone
when heating it. (splattering or popping may occur)
Important Safety Symbols
A Radioactive
D Flammable
Volatile
B Explosive C Corrosive
E Poison
F Biohazard
Lab Safety
1. Reactions that produce toxic gases should be
performed in a —
Should we breath in toxic gases? NO!
How can we trap/remove toxic gases?
A
B
C
D
laboratory fume hood
beaker with a watch glass on top
well-ventilated area of the lab
warm, airtight drying oven
Correct answer: Choice A; a lab fume hood will
trap the gases so that we don’t breath in the fumes
from the toxic gases!
Lab Safety
2 The safest way to dilute concentrated
sulfuric acid is to add —
What is the
rule for
mixing acid
and water?
F a series of small volumes of water to
the acid while stirring
G the acid to water slowly while stirring
constantly
H the acid to a small volume of water
and then add more water
J dilute sulfuric acid to a small volume
of the concentrated acid
Correct answer: G
PAWS—Pour acid into water slowly!
Lab Equipment
PRECISE / PRECISION:
Most exact measurement
*varies for each measurement tool
* What should we look for?
-look for the smallest/finest
increments / scale
PRECISE / PRECISION
9. Which of the following will allow measurement of
a liquid’s volume (mL) with the greatest precision?
Which has the smallest increments?
A. 50 mL cylinder graduated in 1mL increments
B. 100 mL cylinder graduated in 0.5 mL increments
C. 100 mL cylinder graduated in 1mL increments
D. 200 mL cylinder graduated in 5 mL increments
Correct Answer: B; Using this graduated cylinder
with 0.5 mL increments will give you a more
exact/precise measurement of volume.
Volume
*What units are used to measuring
mL
liquid Volume:______
Test Tube
Beaker
Graduated
Pipette
Cylinder
10. Which of the above gives the most precise measurement?
Pipette (smallest increments!)
11. Which of the above should not be used to measure volume?
Beaker- increments are too large & give only an approximate value
Test Tube– only used to “test” or experiment with
Choosing Equipment
Which piece of equipment would
be used to precisely measure
the volume of an acid?
What are the key words?
Precisely – want lots of
increments
Volume – need something
that measures in mL
Correct answer: Choice C
because the graduated
cylinder gives a more
precise measure than the
beaker.
Eliminate choice A (balance measures mass) &
D is a Bunsen burner
Measuring Volume Accurately
12.
46 mL
13.
56 mL
Where is liquid volume read?
At the bottom of the curve called a meniscus.
Reading a Burette
What do we know?
Which is the best
estimate of the
volume of solution
released from the
burette?
A 47.3 mL
B 47.7 mL
C 48.3 mL
D 48.7 mL
Correct answer: B
Initial volume
0.8 mL
Final Volume
48.5 mL
Final volume – Initial volume =
47.7 mL
48.5mL – 0.8 mL =________
Triple Beam Balance
Mass in___________
Grams (g)
Measures________
How do you read the mass on these beams?
498.5 grams
14. Add beams together: 400+90+8.5 = _______
Don’t forget to subtract any mass of the container that held any liquid or powders!
Scientific Method
Scientific Method
1. Observe something
2. State the Problem
3. Form a Hypothesis
-Hypothesis must be testable or measurable
-morals, value of judgment cannot be tested
4. Set Up (Design) an Experiment
-Safety must be considered & planned for
5. Record and Analyze Results/Data
- Making Inferences: Making a prediction based on
information that is provided.
-Includes looking for trends in data.
6. Draw a Conclusion
*Steps don’t have to be in this order but they often are
Go to
Section:
Set Up a Controlled Experiment to test Hypothesis
1. Have Two Groups
a. Control group: all variables constant (the same)
b. Experimental group: receives the independent
variable
2. Types of Variables
a. Control variables: all variables that are kept the
same in all groups
b. Independent variable: the variable that is changed
(by the experimenter) in the group
c. Dependent variable: variable that changes as a
result of the independent variable
3. Only test one variable at a time in an experiment
Go to
Section:
Hypothesis
1. Hypothesis must be testable or measureable
2. Anything that is considered a moral, value or
judgment cannot be tested
This statement is a poor hypothesis because it is not —
A a question
Correct answer: B; This statement
B testable
cannot be measured; it is an opinion!
C observable
D a comparison
Selecting a Correct Hypothesis
Independent variable:
(X-axis) Surface / Material the
object is bounced against
Dependent variable:
(y-axis) How high the object
bounces
Correct answer: D – matches our
prediction
In an activity, a ball is dropped
from a height of 100 cm onto
five different materials. The
rebound height of each drop is
shown in the graph. Which of
the following describes the
hypothesis most likely being
tested?
A The mass of the ball affects the
rebound height.
B The material the ball is made of
affects the rebound height.
C The height the ball is dropped from
affects the rebound height.
D The surface the ball is dropped
onto affects the rebound height.
Testing Hypotheses
The following hypothesis refers
to iron in the topsoil found on
an island formed from
limestone.
How did the topsoil get on the
island?
Dust clouds; carried by air
currents
Where did the dust clouds come
from?
Africa
Which study would most
likely be used to investigate
this hypothesis?
F Tracking dust clouds with satellite
photos
G Determining the effects of iron on
limestone
H Calculating erosion rates in
African limestone mines
J Analyzing the content of comet
dust clouds
Answer: F – Best matches
answers to questions
Identifying variables
16. A medical researcher hypothesizes that a newly
developed medication can reduce high blood pressure. Which
of these would most likely be the dependent variable in a
study involving this medication?
A The number of participants
in the study
B The ages of people treated
for high blood pressure with
other medications
C The blood pressure of the
participants in the study
D The number of people
treated for high blood
pressure with other
medication
Independent variable:
New developed medicine
Dependent variable:
Blood pressure
Correct answer: C – matches our
prediction
Experimental Design: The Control Group
Groups
A valid study would include a
control group containing —
F bean seed, tomato seed, sunflower
seed, and water
G water and 2% root hormone
H water only
J bean seed, tomato seed, sunflower
seed, water, and 1% root hormone
Correct answer: F
of root hormone
Independent variable: Concentration
___________________________
Root growth
Dependent variable: _____________
Control group
What’s missing? _______________
Bean seed, tomato seed, sunflower
seed, & water – added to control cup
What should the control group look like?_________________________________
Making Inferences
Making a prediction based on information that is
provided.
Includes looking for trends in data.
The graph compares absenteeism
of elementary school students
who wash their hands properly
with absenteeism of students who
fail to wash their hands properly.
Which inference could best be
supported by these data?
F Proper hand washing may increase
attendance among elementary school
students.
What can you tell by just reading
the graph?
Kids miss less school if they
wash their hands correctly.
Correct Answer: F ; Best
matches our initial answer!
G Older students have developed better
hand-washing habits than younger
students
H Some elementary school classes teach
correct hand-washing methods to
students
J Improper hand washing is a common
practice among most elementary school
students
Promotional Claims
Can a product do what it claims it can do?
Analyzing
Promotional
Claims
Correct answer: D
Which conclusion about AvexTec is supported by information in this
advertisement?
A AvexTec is available over the counter at local pharmacies and grocery
stores.
B People who take AvexTec every day will seldom experience pain from
migraines.
C Research indicates that AvexTec prevents migraine headaches.
D AvexTec can be prescribed to reduce pain from migraines.