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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 well-ventilated 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
D
BA C
FE
Radioactive Explosive Corrosive
Flammable Volatile
Poison Biohazard
Lab Safety 1. Reactions that produce toxic gases should be
performed in a —
A laboratory fume hood B beaker with a watch glass on top C well-ventilated area of the lab D warm, airtight drying oven
Should we breath in toxic gases? NO!
How can we trap/remove toxic gases?
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!
2 The safest way to dilute concentrated sulfuric acid is to add —
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
Lab Safety
Correct answer: G PAWS—Pour acid into water slowly!
What is the rule for mixing acid and water?
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 / PRECISION9. Which of the following will allow measurement of
a liquid’s volume (mL) with the greatest precision?
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
Which has the smallest increments?
Correct Answer: B; Using this graduated cylinder with 0.5 mL increments will give you a more
exact/precise measurement of volume.
Graduated Cylinder
Beaker
Pipette
Test Tube
*What units are used to measuring liquid Volume:______mL
10. Which of the above gives the most precise measurement?
11. Which of the above should not be used to measure volume?
Pipette (smallest increments!)
Beaker- increments are too large & give only an approximate value
Test Tube– only used to “test” or experiment with
Volume
Choosing Equipment Which piece of equipment would
be used to precisely measure the volume of an acid?
Eliminate choice A (balance measures mass) & D is a Bunsen burner
Correct answer: Choice C because the graduated cylinder gives a more precise measure than the beaker.
Precisely – want lots of increments
Volume – need something that measures in mL
What are the key words?
Measuring Volume Accurately
12. 13.46 mL 56 mL
Where is liquid volume read?
At the bottom of the curve called a meniscus.
Reading a Burette
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 mLInitial volume Final Volume
Final volume – Initial volume =
48.5mL – 0.8 mL =________ 47.7 mL
Correct answer: B
0.8 mL 48.5 mL
What do we know?
Triple Beam BalanceMeasures________ in___________Mass Grams (g)
14. Add beams together: 400+90+8.5 = _______
How do you read the mass on these beams?
498.5 grams
Don’t forget to subtract any mass of the container that held any liquid or powders!
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
Scientific Method
Go to Section:
Set Up a Controlled Experiment to test Hypothesis
Go to Section:
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
Hypothesis1. Hypothesis must be testable or measureable2. Anything that is considered a moral, value or
judgment cannot be tested
This statement is a poor hypothesis because it is not —A a questionB testableC observableD a comparison
Correct answer: B; This statement cannot be measured; it is an opinion!
Selecting a Correct Hypothesis 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.
Independent variable:
Dependent variable:
(X-axis) Surface / Material the object is bounced against
(y-axis) How high the object bounces
Correct answer: D – matches our prediction
Testing Hypotheses The following hypothesis refers
to iron in the topsoil found on an island formed from limestone.
Which study would most likely be used to investigate this hypothesis?
F Tracking dust clouds with satellite photosG Determining the effects of iron on limestoneH Calculating erosion rates in African limestone minesJ Analyzing the content of comet dust clouds
How did the topsoil get on the island?
Where did the dust clouds come from?
Dust clouds; carried by air currents
Africa
Answer: F – Best matches answers to questions
Identifying variables
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:
Dependent variable:
New developed medicine
Blood pressure
Correct answer: C – matches our prediction
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?
Experimental Design: The Control Group A valid study would include a
control group containing — F bean seed, tomato seed, sunflower seed, and waterG water and 2% root hormoneH water onlyJ bean seed, tomato seed, sunflower seed, water, and 1% root hormone
Independent variable: ___________________________
Dependent variable: _____________
Concentration of root hormone
Root growth
What’s missing? _______________Control group
What should the control group look like?_________________________________
Bean seed, tomato seed, sunflower seed, & water – added to control cup
Correct answer: F
Groups
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.
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
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!
Analyzing Promotional
Claims
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.
Correct answer: D
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