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.
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
Practice! • The solution: The Thermometer: • QuaLitativeQuaNtitative • The metal: The NaCl sample: • QuaLitativeQuaNtitative • The syrup: The HCl solution: • QuaLitativeQuaNtitative • Two substances: The length: • QuaLitativeQuaNtitative
What’s the difference?? Scientific Theory Scientific Law 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! 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!
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 Mistake or Source of Error? Human Mistake 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 • WHOOPS!!! • Generally procedural mistakes • Example: Procedure states to measure 14.0 mL of water and person measures 15.0 mL of water.
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
Wear ___________________________ at all times!! • Wear _____________________ to all labs to prevent chemical spills and broken class on your feet. • Wear an ________________________ during all labs. • ______________________________ is NOT allowed. • ______________________________ before leaving. • Pull back hair into a ponytail for labs. GOGGLES Closed-toe shoes Apron Eating and Drinking – Includes chewing gum Wash hands
Use a ________________ for any reaction that may produce harmful/toxic gases. • Never put extra chemicals back in the ____________, you may contaminate the rest of the chemical. • Always dispose of chemicals the way the __________ tells you to do so! • Smell chemicals by _____________________. • 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? • ALWAYS tell the _______________________!!!! • Spills • Spill an acid, add ___________________ to neutralize it before wiping it up. • Spill a base, add ____________________ to neutralize it before wiping it up. • Use the __________________ for chemicals in your eye and the __________________ if harmful chemicals get on your body. • 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 for The specified Hazard 0 __________________________ 1 __________________________ 2 __________________________ 3 __________________________ 4 __________________________ No Hazard Slight Hazard Hazardous Extreme Hazard Deadly Blue: Health Hazard Red: Flammability Yellow: Reactivity White: Special information
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?
Graphing…… Why do we do it? To communicate information or data visually
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 proportional Directly 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