Chemistry 112.3 Fall Semester 2011

1. Chemistry 112.3Fall Semester 2011 Ian Burgess Office Number : Thorv. 256 Telephone : 966-4722 Email : ian.burgess@usask.ca

2. Chapter 1 : Matter, Measurement and Problem Solving • Outline • Atoms and Molecules • The Scientific Approach • The Classification of Matter • Properties and Changes of Matter • Energy • Units and the S.I. system • Reliability of a measurement • Solving Chemical Problems

3. Atoms and Molecules • atoms • are submicroscopic particles • molecules • two or more atoms attached together • molecules come in different shapes and patterns • Chemistry is the science that seeks to understand the behavior of matter by studying the behavior of atoms and molecules. Atoms and Molecules

4. The Scientific Approach • Hypothesis – a tentative interpretation or explanation for an observation • falsifiable – confirmed or refuted by other observations • tested by experiments – validated or invalidated • when similar observations are consistently made, it can lead to a Scientific Law • a statement of a behavior that is always observed • summarizes past observations and predicts future ones • a hypothesis is a potential explanation for a handful of observations • a theory is a general explanation for the manifestation and behavior of all nature • models • pinnacle of scientific knowledge • validated or invalidated by experiment and observation The Scientific Approach

5. The Scientific Approach

6. The Classification of Matter solid liquid gas Classifying Matter

7. Solids • The particles in a solid are packed close together and are fixed in position Classifying Matter

8. Gases • in the gas state, the particles have complete freedom from each other. Liquids • can take the shape of their container and can flow – however, they don’t have enough freedom to escape and expand to fill the container. • in the gas state, there is a lot of empty space between the particles Classifying Matter

9. matter whose composition does not change from one sample to another is called a pure substance. • matter whose composition may vary from one sample to another is called a mixture. Classifying Matter

10. Properties and Changes of Matter • Composition – refers to the parts or components of a sample of matter and their relative proportions. • Physical property - acharacteristics a substance displays without changing its composition. • Chemical property - is a characteristic a substance displays only when changing its composition. • Physical change –the physical properties of a sample change but its composition remains unchanged. • Chemical change –matter is converted to a new kind, with a different composition. More about matter

11. How to further classify matter ? Classifying Matter

12. An Example of a Physical Change… • changes that alter the state or appearance of the matter without altering the composition are called physical changes More about matter

13. An Example of a Chemical Change… • changes that alter the composition of the matter are called chemical changes More about matter

14. Energy • changes in matter, both physical and chemical, result in the matter either gaining or releasing energy • kinetic energy is energy of motion. • potential energy is energy that is stored in matter. • you can interconvert kinetic energy and potential energy • Law of Conservation of Energy whatever process you do that converts energy from one type or form to another, the total amount of energy remains the same Energy

15. Units of Measurement SI : Système Internationale Units

16. Units

17. Derived Units Definition :Combinations of the base quantities of length, mass, time, temperature, etc… Examples : Units

18. The Reliability of a Measurement What is the volume in this graduate cylinder ? All measurements are susceptible to error. Reliability of a measurement

19. Error Accuracy - How close your experimental measurement is to the correct answer. Precision - Refers to the degree of reproducibility of a measured quantity. Reliability of a measurement

20. Example Four groups (each group has 5 students) of Chem 112 students are asked to measure a desk with meter sticks. However, one meter stick is incorrectly labelled. The correct length of the desk is 180 cm. Below are the four sets of data Group A 168 cm 170 cm 169 cm 167 cm 168 cm Group B 182 cm 175 cm 177 cm 183 cm 185 cm Group C 180 cm 179 cm 179 cm 180 cm 181 cm Group D 168 cm 173 cm 170 cm 165 cm 174 cm Reliability of a measurement

21. Significant Figures Reliability of a measurement

22. Significant Figures How many significant figures are in each of the following? 0.04450 m 5.0003 km 1.000 × 105 s 0.00002 mm Reliability of a measurement

23. Carrying Significant Figures in Calculations • when multiplying or dividing measurements with significant figures, the result has the same number of significant figures as the measurement with the fewest number of significant figures 5.02 × 89,665 × 0.10 = 45.0118 = 45 5.892 ÷ 6.10 = 0.96590 = 0.966 Reliability of a measurement

24. when adding or subtracting measurements with significant figures, the result has the same number of decimal places as the measurement with the fewest number of decimal places 5.74 + 0.823 + 2.651 = 9.214 = 9.21 4.8 - 3.965 = 0.835 = 0.8 Reliability of a measurement