Notes 1.3 Intro to Chemistry

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

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

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

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

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

  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  

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

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 100 Accepted Accepted

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?

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