Unit 1 Foundations of Chemistry – Expectations, Lab Safety, Measurement and Analysis

Math – the language of chemistry  Pre-Test  Review Pre-Test

Lab Safety

Why is Lab Safety Important?  Lab safety is a major aspect of every lab based science class.  Lab safety rules and symbols are needed so that students do not injure themselves or their classmates.

Lab Safety  Video  Demos  Why do you need to wear eye protection? I wear contacts?  What happens if I spill acid on my skin?  Why do I have to label materials?  Why shouldn’t I drink in the lab and why can’t I dump everything down the sink?

Lab Safety Equipment  PPE (Personal Protective Equipment)  Safety Shower  Eye Wash  Fire Extinguisher  Fire Blanket

Lab Safety Equipment Safety ShowerSafety Goggles Eye Wash

Waste Disposal  First ask your teacher where/how to dispose of waste.  Never pour anything down the drain unless you are told to do so. It can affect the community’s water, plants, animals & people.  A waste bottle will be supplied for substance that cannot go down the drain

Fire Drill  Why should I pay attention? Why should I pay attention?  Where do we go?  Class leader?

Lab Safety Continued  Lab Safety Contract  Lab Safety Crossword Puzzle

Nature of Science  Mystery Solutions Lab

12 The Nature of Science* Humans have a need to:  Understand the world around them  Change their environment using technology in order to accommodate what they understand or desire  Natural curiosity vs. making life better Science begins with observations, therefore, much of science is purely descriptive. Science uses both deductive and inductive reasoning. * Adapted from Next Generation Science Standards

13 The Nature of Science* Basic Understandings of Science  Scientific investigation uses a variety of methods (NOT just scientific method)  Scientific knowledge is based on EVIDENCE!  Scientific knowledge can change based on new evidence  Use models, theories, laws, mechanisms to describe natural phenomenon  Assumes order in nature  Human’s “do” science  Addresses questions about the natural AND material world * Adapted from Next Generation Science Standards

Chemistry Lab Analysis

Lab Analysis  Chemistry labs are designed to investigate a problem or questions  Procedure designed  Data is collected.  Analysis section interprets the data

Lab Analysis  3 Tools for Lab Analysis:  1. Observation & Inferences  2. Accuracy & Precision  3. Graph Construction & Analysis

(I) Observation & Inference

Observations  Any information collected with the senses.  The skill of describing scientific events.

Observations 22 Types QQualitative observations = descriptive observations, no numbers involved (i.e. color, texture, smell) QQuantitative observations = observations described by a numbered measurement. (i.e. 5 meters, 30 seconds, 32 mL)

Inference  Conclusions or deductions based on observations *May be influenced by prior knowledge.  Process of drawing a conclusion from given evidence.

Tracks like these are common in parts of New England and in the southwestern United States. What do you OBSERVE? What can you INFER?

Now what do you think?

Infer what happened based on your observations.

Observation Activity #1  Observe the picture for exactly 30 seconds. Look at everything you think might be important.picture  After 30 seconds, answer the questions on the next page on a sheet of paper.  How observant were you? Compare your answers to the picture.

Questions: 1. Are there cars parked on the sides of the road? 2. What color is the pickup truck driving in the road? 3. Any minivans around? 4. What does the blue sign say? 5. What’s the speed limit? 6. Are there any pedestrians on the road?

Question 1 Are there cars parked on the side of the road?

Question 2 What color is the pickup truck driving in the road?

Question 3 Any minivans around?

Question 4 What does the blue sign say?

Question 5 What's the speed limit?

Question 6 Are there any pedestrians on the road?

Observation Activity #2  Observe the picture for exactly 30 seconds. Look at everything you think might be important.picture  After 30 seconds, answer the questions on the next page on a sheet of paper.  How observant were you? Compare your answers to the picture.

Questions: 1. How many cars were in the intersection? 2. Across the street, are there any parked cars on the side? 3. What is the color of the van in the intersection? 4. Are there any other potential witnesses? 5. What was the speed limit? 6. Was there anyone parked in the first parking spot?

Question 1 How many cars were in the intersection?

Question 2 Across the street, are there any parked cars on the side?

Question 3 What is the color of the van in the intersection?

Question 4 Are there any other potential witnesses?

Question 5 What is the speed limit?

Question 6 Was there anyone parked in the first parking space?

Accuracy & Precision Two important points in measurement

Accuracy Accuracy = the extent to which a measured value agrees with a standard value  Accuracy of a device/tool  Accuracy of reader Beware of Parallax – the apparent shift in position when viewed at a different angle.

Graduated Cylinder – Meniscus and Parallax

Example: Accuracy Who is more accurate when measuring a book that has a true length of 17.0 cm? Susan: 17.0 cm, 16.0 cm, 18.0 cm, 15.0 cm Amy: 15.5 cm, 15.0 cm, 15.2 cm, 15.3 cm

Precision Precision = the degree of exactness of a measurement that is repeatedly recorded. (smallest range of values) Which set is more precise? Susan: 18.2, 18.4, Amy: 17.9, 18.3, Tom: 16.8, 17.2, 19.44

Example: Precision Who is more precise when measuring the same 17.0 cm book? Susan: 17.0 cm, 16.0 cm, 18.0 cm, 15.0 cm Amy: 15.5 cm, 15.0 cm, 15.2 cm, 15.3 cm

Exit Quiz: Evaluate whether the following are precise, accurate or both. Figure #1 Figure #2 Figure #3

 Percent Error  Percent deviation from the true (actual) value  Measure of accuracy % error = l True – experimental l x 100 True

II. Percent Error Example: AA student measured the density of an object to be g/ml. The true density of the object is 2.699g/ml. What is the percent error of the experiment? Is the student accurate? ll g/ml – g/ml l x 100 = 7.040% error g/ml  Y Yes, student is accurate. AAnything below 10% is acceptable as accurate. The closer to 0% the better!

Why is it so important to be accurate and precise as a chemist? MMedicine – certain amounts can turn into lethal dosages WWork with flammable products TTo insure reproducible products (cosmetics, soap, hair products…) TTo insure quality of our environments (air and water quality)

(III) Graphing

2 Types of Graphs used in Chemistry Lab Line Graph  A line graph shows the relationship between your variables. Usually used to show how things change over time.

2 Types of Graphs used in Chemistry Lab Bar Graph  A bar graph is used to show a comparison of different trials or different experimental groups.