1 / 16

Chapter 1 What is Chemistry?

Chapter 1 What is Chemistry?. It is a broad science that touches nearly every aspect of life. Most things lead to chemistry (water ecology, farming, medicine, house wife/mother, masonry …. Why study chemistry?. It plays a role in many areas of life (knowledge is power).

caesar
Télécharger la présentation

Chapter 1 What is Chemistry?

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 1What is Chemistry?

  2. It is a broad science that touches nearly every aspect of life. • Most things lead to chemistry (water ecology, farming, medicine, house wife/mother, masonry …..

  3. Why study chemistry? • It plays a role in many areas of life (knowledge is power). • Many occupations require this knowledge. • It is fun to know how things work. • It helps develop the mind (reasoning power and observation skills). It is like weight training for the mind. • It can be very beautiful (like great music or art).

  4. The Scientific Method • We make an observation. • We ask a question. • We formulate a tentative explanation (a hypothesis). • We design an experiment to test the hypothesis. • We analysis the result and conclude if we are right. • Report results and ask a new question.

  5. How to design a good experiment • Experimental results are typically compared to the normal situation. • The control is that trial of the experiment in which everything is kept normal. (The control is the standard.) • The variable is that one aspect that is changed in each trial.

  6. After many experiments and observations may develop: • A theory – It is a broad overview of understanding that explains things. (example: the molecular theory of matter) • A natural law – is an observation that nature always behaves the same way. (example: mass is conserved in chemical reactions)

  7. The Math Tool Kit • International system of units (SI) • Length – meters (m) • Mass – gram (g) • Volume – liter (L) • See page 18

  8. Units can be increased or decreased by using a prefix Prefix Abbreviation Meaning Nano n 10-9 Micro µ 10-6 Milli m 10-3 Centi c 10-2 Deci d 10-1 Kilo k 103 Mega M 106

  9. Scientific Notation • Place the decimal point behind the first non-zero number and use a power of ten to indicate the magnitude of the number. Change 1,230,000,000 to scientific notation (1.23 x 109) Change 0.0000001401 to scientific notation (1.401 x 10-7) Multiply the above two numbers 172.323

  10. Uncertainty in measurements and calculations • Exact numbers – definitions (example 12 inches = 1 foot) • Inexact numbers – measurements (example: 12.1 inches, 2.54 cm = 1 inch) • A measurement can be off by as much as ½ of the smallest increment (the last digit is an estimate) (example: 1.2 + or - .05g) The true mass could be closer to 1.15 or 1.25 than to 1.20g.

  11. Percent Uncertainty in Inexact Numbers % uncertainty = uncertainty/value x 100 Example: mass of 1.2 g % uncertainty = 0.05g/1.2g (100) Uncertainty = 4.2% Exact numbers have 100% certainty

  12. Calculate the % uncertainty in each of the following measurements. • 111.1 grams • .045% • 11 grams • 4.5% • .11 grams • 4.5% • Which value can you have the most confidence in?

  13. Reliability in Measurement • Precision – the smallest increment of measurement, gives the same results again and again • Accuracy – how close the value is to the true value Target Analogy

  14. Significant Digits • To reflect the degree of confidence that we can have in our number, we use rules in reporting the number. • These rules are the significant digit rules. • The greater number of significant digits, the lower the uncertainty and the more confidence we have in the number.

  15. See the Significant Figures sheet • The more significant digits, the more confidence we can have in the number. • Complete the sig. digit worksheet.

  16. Why use scientific notation? • It is good for very large or very small numbers. • It is also the best way to show the number of significant digits. • Complete practice worksheets. (Factor-label method)

More Related