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

Chemistry Lab Analysis

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.