unit 1 foundations of chemistry – expectations, lab safety, measurement and analysis
TRANSCRIPT
Unit 1Foundations 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 EquipmentSafety Shower Safety GogglesEye 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? Where do we go? Class leader?
Lab Safety Continued Lab Safety Contract Lab Safety Crossword Puzzle
Nature of Science Mystery Solutions Lab
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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
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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
Lab AnalysisChemistry labs are designed to
investigate a problem or questions Procedure designed Data is collected. Analysis section interprets the data
Lab Analysis3 Tools for Lab Analysis:
1. Observation & Inferences2. Accuracy & Precision3. Graph Construction &
Analysis
(I)Observation & Inference
Observations Any information collected with the
senses. The skill of describing scientific events.
Observations
2 TypesQualitative observations = descriptive
observations, no numbers involved (i.e. color, texture, smell)
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.
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?
Yes
Question 2
What color is the pickup truck driving in the road?
Blue
Question 3
Any minivans around?
Yes
Question 4
What does the blue sign say?
Yard Sale
Question 5
What's the speed limit?
35 mph
Question 6
Are there any pedestrians on the road?
No
Observation Activity #2 Observe the picture for exactly 30
seconds. Look at everything you think might be important.
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 1How many cars were in the
intersection? 2
Question 2Across the street, are there any parked cars on the side? Yes
Question 3What is the color of the van in
the intersection? White
Question 4Are there any other potential
witnesses?Yes
Mowing the lawn
Question 5What is the speed limit? 35 mph
Question 6Was there anyone parked in
the first parking space? No
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
PrecisionPrecision = 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 ,
18.35Amy: 17.9 , 18.3 , 18.85Tom: 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 ErrorPercent deviation from the true (actual) valueMeasure of accuracy
% error = l True – experimental l x
100 True
II. Percent Error
Example:
A student measured the density of an object to be 2.889 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 2.699 g/ml – 2.889 g/ml l x 100 = 7.040% error
2.699 g/ml
Yes, student is accurate. 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?
Medicine – certain amounts can turn into lethal dosages
Work with flammable products To insure reproducible products (cosmetics,
soap, hair products…) 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.