THE LAB AND SCIENTIFIC METHOD

- the rules and procedures for the pursuit of knowledge involving the finding and stating of a problem, the collection of facts through observation and experiment, and the making and testing of ideas that need to be proven right or wrong.Hypothesis: The scientist formulates a possible explanation for the observation.A valid hypothesis meets two criteria:1) It must use conditional language… such as “might” or “may” statements.2) It must be testable.

Scientific Method

The Strange Case of BeriBeri

• What was the original hypothesis?– Beriberi is caused by a bacteria

• How was the hypothesis tested?– Injected the blood of sick people into chickens to see if

the chickens became sick• Should the hypothesis be supported or rejected?– Rejected: control group became sick

• New Hypothesis?– The lack of Thiamine in polished rice may be causing

people to contract BeriBeri

Practice!

• Dr. Leggett: – Not valid: not testable

• Mr. Koder: – Valid: testable and conditional

• Leaf color:– Not valid: not conditional

QUALITATIVE AND QUANTITATIVE DATA

Types of Data: The scientist makes qualitative and/or quantitative observations.

Qualitative: based on descriptions(ex: color, clarity, texture)

Quantitative: based on numbers(ex: mass, volume, length)

Practice!

• The solution: The Thermometer:– QuaLitative QuaNtitative

• The metal: The NaCl sample:– QuaLitative QuaNtitative

• The syrup: The HCl solution:– QuaLitative QuaNtitative

• Two substances: The length:– QuaLitative QuaNtitative

LAWS, THEORIES,

AND

VARIABLES

This is a concise and factual statement that is meant to prove an observation.

It is accepted to be true and universal by scientists.

It is often expressed as a mathematical equation.

Find an example of a scientific law and write it in your notes!

A theory is an explanation of a natural or physical phenomenon based upon proven multiple hypotheses and verified multiple times by independent researchers.

Theories will very often include laws in order to prove their point.

Find an example of a scientific theory and write it in your notes!

What’s the difference??

Scientific Law Scientific Theory

Independent Variable

Dependent Variable

Control Variable(s)

Variable that the scientist is changing

Affects the Dependent Variable

Graphed on the X-Axis Variable that is measured in response

to a change in the independent variable.

These are the “results” which you, the scientist, measure and record

Graphed on the Y-axis Held CONSTANT by the scientist to allow

comparison of only Independent and Dependent Variables

CAREFUL*** This is different from a control group

Ex…Maintaining Constant Temperature in the lab during experimentation

Practice!

• How could you test the claim?

• What would your beginning question be?

• What would your independent variable be?

• What would your dependent variable be

• What would be some control variables?

Have several brands and run them over the same amount of dirt: make measurements initially and after the vacuum passed over it.

Which vacuum will pick up the most dirt?

Brands of vacuums

Amount of dirt

Only bagged vacuums: same and initial kind of dirt, same amount of time over the dirt: all bags empty initially ect…

HUMAN MISTAKES

AND SOURCES OF ERROR

Human Mistake or Source of Error?Human Mistake

• WHOOPS!!!– Generally procedural

mistakes– Example: Procedure

states to measure 14.0 mL of water and person measures 15.0 mL of water.

Source of Error• Limitation of Procedure• Some questions to ask yourself to determine

sources of error:– Could the procedure be done more precisely? (Think

measurements.)– Could the procedure be done with less contamination?– Were the variables to be held constant REALLY held

constant?– What assumptions were made in the collecting of data?– Was there a level of subjectivity in interpreting the

data?

• Procedure states to measure 14.0 mL of water. Person measured 14.0 mL of hot water one time and 14.0 mL of cold water a different time – i.e. the temperature of the water was not controlled or constant

Practice!• Miscalculation:

– Mistake• Temperature of room:

– source of error• Transferring powder:

– source of error• Used too much NaCl:

– mistake• Wrong order:

– mistake• Hand drawn graph:

– source of error• Twenty drops:

– source of error

LAB RULES AND

NFPA DIAMOND

1. Wear ___________________________ at all times!!

2. Wear _____________________ to all labs to prevent chemical spills and broken class on your feet.

3. Wear an ________________________ during all labs.

4. ______________________________ is NOT allowed.

5. ______________________________ before leaving.

6. Pull back hair into a ponytail for labs.

GOGGLES

Closed-toe shoes

Apron

Eating and Drinking – Includes chewing gum

Wash hands

7. Use a ________________ for any reaction that may produce harmful/toxic gases.

8. Never put extra chemicals back in the ____________, you may contaminate the rest of the chemical.

9. Always dispose of chemicals the way the __________ tells you to do so!

10. Smell chemicals by _____________________.

11. Point heated test tubes _______________ from other people and yourself.

12. Always add ___________ into ___________ when diluting the acid.

Fume Hood

Stock container

The teacher

wafting

away

acid water

WHAT SHOULD I DO IF AN EMERGENCY HAPPENS?1. ALWAYS tell the _______________________!!!!

2. Spills

a. Spill an acid, add ___________________ to neutralize it before wiping it up.

b. Spill a base, add ____________________ to neutralize it before wiping it up.

3. Use the __________________ for chemicals in your eye and the __________________ if harmful chemicals get on your body.

4. For small fires, __________________________ and if somebody is on fire use the ____________________.

teacher

Base: baking soda

Acid: vinegar

Eye wash

Safety shower

Invert a beaker

Fire blanket or safety shower

Safety Vocabulary: _____________ eat away at objects, attacks & burns skin

_____________ poisonous _____________ easily set on fire; combustible _____________ can cause cancer _____________ spontaneously emits radiation resulting from changes in the nucleus of atoms _____________ causes a rash or allergic reaction

Corrosive

Toxic

Flammable

Carcinogen

Radioactive

Allergen/irritant

Numbers indicate the amount of danger forThe specified Hazard

0 __________________________

1 __________________________

2 __________________________

3 __________________________

4 __________________________

No Hazard

Slight Hazard

Hazardous

Extreme Hazard

DeadlyBlue: Health HazardRed: FlammabilityYellow: ReactivityWhite: Special information

MSDS FORMS

MSDS: What and Why???

***To the left, you will find the first page of a MSDS for highly concentrated Hydrochloric Acid. We commonly use this chemical in lab, but at much lower concentration levels. Answer the following questions using the MSDS sheet:

Do we need to be concerned with flammability for this substance?

What should we do if someone accidentally swallows this substance?

How should we store this substance?

What are some health hazards we should be concerned of with this substance?

Should this substance be used in a fume hood?

What happens if this substance touches skin?

If this substance is spilled, how would you clean it up?

LAB EQUIPMENT

Equipment Name

Picture Qualitative/Quantitative Description of Use

Beaker QuaLitative Large mouth glass containers used to contain approximate volumes of liquid

Erlenmeyer Flask QuaLitative

Glass container used to contain approximate volumes of liquid. Small mouth accommodates a stopper for storage or shaking.

Transfer Pipette QuaLitativeUsed to measure and deliver approximate volumes of liquids. Often used in place of a dropper.

Graduated Pipette Quantitative Used to precisely deliver variable quantities of

liquid.

Graduated Cylinder Quantitative Used to measure and deliver precise volumes of

liquids.

Volumetric Flask Quantitative

Designed to precisely contain a specific volume. Commonly used when accurately making aqueous solutions.

Buret QuantitativeLong tube with a stopcock that opens and closes. It is used to precisely deliver solutions, especially in a titration

Electronic Balance Quantitative An electronic scale used to precisely measure

the mass of a substance.

Triple Beam Balance Quantitative A scale that uses counterweights to precisely

measure the mass of a substance.

Thermometer Quantitative

A sealed glass tube containing a liquid that expands and contracts due to a change in temperature. Used to precisely measure the temperature of a substance.

Test Tube QuaLitative Glass cylinder that holds liquids being tested in an experiment.

Equipment Name Picture Function

Scoopula A folded piece of metal that is used to transfer solids

Test Tube Holder Spring metal holder used to hold or transfer hot test tubes

Test Tube Clamp Clamps a test tube or other equipment onto a ring stand

Wire Gauze Used to help support equipment and spread the heat of a burner flame

Striker Has a flint that sparks to initiate flame on Bunsen burners; DO NOT PLAY WITH THESE AND WEAR OUT THE FLINT!

Spot Plate A plastic or porcelain plate with wells used to test reactions during micro labs; sometimes called a “well plate”

Ring Stand Long metal pole on a base; along with clamps, it is used as a support of equipment set-ups

Ring Clamp Ring-shaped clamp that attaches to the ring stand to support equipment

ALL ABOUT GRAPHS

Graphing…… Why do we do it? To communicate information or data visually

Type of Graph Use Example

Circle Graph or Pie Chart To illustrate numerical proportions of data compared to the whole

Bar Graph or Histogram

To illustrate relative sizes – it is a graphical display of data using bars of different heights

*Histograms are similar to bar graphs except a histogram groups numbers into ranges.

Line Graph

To illustrate how data changes over time

Scatter Plot To illustrate the relationship between two sets of data

Inversely or Directly Proportional??Inversely Proportional is… - opposite in order or effect, ex. When one variable increases (more water you drink) the other variable decreases (less thirsty you are)- product of two variables always equals a constant, ex. 4 = xy, the variables x & y are inversely proportionalDirectly Proportional is… - same in order of effect, ex. When one variable increases (the more hours you work) the other variable increases (the more you get paid)- one variable is always the product of the other variable, ex. 4y = x, the variables x & y are directly proportional