1. Notes 1.3 Intro to Chemistry

2. I. Matter Matter is anything that has mass and takes up space.
Most things are matter

3. Mass versus weight Mass is the amount of matter in an object
Mass is constant (does not depend on gravity)
Mass is measured using a balance
Weight relates mass and the effect of gravity
Weight changes based on the force of gravity
Weight is measured using a scale

4. Scientific Method
A systematic approach to problem solving, which uses a step by step approach
Observation
Hypothesis
Experiments
Data Analysis
Conclusions
Retest

5. Observation A piece of information obtained during an experiment
Can be qualitative or quantitative
Qualitative - described using words
Ex. shape, color, texture
Quantitative – described using numbers
Ex. Mass, weight, length

6. Hypothesis
Your educated guess or tentative explanation why something happened
Must be supported by data

7.   Experiments
A set of controlled observations used to test the hypothesis
Only one variable can be tested at a time
A variable is a quantity or condition with more than one value

8. Data analysis
Accuracy- how close you are to the actual value (bullseye)
Precision- how repeatable the result is

9. Absolute Error
The difference between the right and wrong answer
EA = | observed – accepted |
Relative error
The percentage off from the accepted value
ER = EA x 100 ER = |observed – accepted| x Accepted Accepted

10. Example: Mary determines the density of copper to be 8. 7 g/mL
Example: Mary determines the density of copper to be 8.7 g/mL. If the actual density is 9.0 g/mL, what is Mary’s absolute error and relative error?

11. Theory (attempts to explain why)
Conclusion
Judgment based on the obtained information
Can be demonstrated using a model
Theory (attempts to explain why)
A conclusion that has been supported by many experiments
Still subject to change if new data comes along
Scientific Law
A relationship that is supported by experiments and scientists