TAKS Objective 1The 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 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!

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

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!

Promotional ClaimsCan a product do what it claims it can do?

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