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Introduction to Chemistry

Introduction to Chemistry. Part I Chemistry and Technology. Chemistry. The study of: the composition (make-up) of matter the changes that matter undergoes. What is matter?. Anything that: has mass and occupies space (volume). Mass vs Weight.

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Introduction to Chemistry

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  1. Introduction to Chemistry

  2. Part I Chemistry and Technology

  3. Chemistry The study of: • the composition (make-up) of matter • the changes that matter undergoes

  4. What is matter? • Anything that: • has mass and • occupies space (volume).

  5. Mass vs Weight • Mass: a measure of the amount of matter that an object contains. (SI unit kilogram, kg) • Weight: The force with which the earth pulls on an object. (SI unit Newton, N)

  6. The 5 Branches of Chemistry • Inorganic • Organic • Analytical • Physical • Biochemistry

  7. Inorganic Chemistry • The study of chemicals that can but do not have to contain carbon. • The study of chemicals making up nonliving things

  8. Organic Chemistry • The study of chemicals that contain carbon. • Origin: study of chemicals in living organisms.

  9. Organic or Inorganic ? • Sulfuric Acid H2SO4 • Methane CH4 • Hydrochloric Acid HCl • Ethane C2H6

  10. Analytical Chemistry • Composition of matter. Ex:Mass SpectrometerGas Chromatograph http://besg.group.shef.ac.uk/Facilities/Images/gcms.JPG

  11. Physical Chemistry • The study of : • The mechanism • The rate • The energy transfer that happens when matter undergoes change.

  12. Biochemistry • Study of processes that take place in organisms.

  13. Science • What? • Why? • How? • When?

  14. Science and Technology • Science  Pure • Does not necessarily have an application. • Technology  Applied • Has practical applications in society. • Engineering.

  15. Question: Science or Technology? Studying or forming aspirin in a lab in small scale (small amounts).

  16. Question: Science or Technology? • Producing aspirin tablets so that consumers can use them.

  17. Example: Discovery of Nylon by Wallace Carothers in 1930’s https://www.acs.org/content/acs/en/education/whatischemistry/landmarks/carotherspolymers.html

  18. Microscopic- Macroscopic • Micro –(small) • Microscopic- objects can be seen with a microscope. • Macro-(from afar) • Macroscopic- objects are seen without a microscope.

  19. Every Experiment must have… • Hypothesis- an educated guess based on prior knowledge; can be tested by experimentation • Independent Variable- the one variable being tested, changed, and manipulated by the scientist (There is only ONE Independent Variable per experiment.) *goes on x-axis when graphing • Dependent Variable- the variable that changes in response to the independent variable (usually it is what you are measuring/collecting data on) *goes on y-axis when graphing

  20. Remember that you NEVER prove anything; Your hypothesis is either accepted or rejected!

  21. Control Group- must have one group/trial in the experiment that lacks the independent variable – used for comparison • Experimental Group(s)-the groups/trials that contain the independent variable • Controlled Variables- things that need to stay constant throughout the experiment

  22. Theory vs. Law • Theory – an explanation of a natural phenomenon supported by many observations and experiments over time. Supported by evidence and enables scientist to make accurate predictions. • Law – describes relationships under certain conditions in nature. Does not explain why an event occurs, just describes the relationship.

  23. Theory or Law? • A hypothesis that is supported by experimental results, many times. • It cannot be explained why the relationship exists. • All energy cannot be created or destroyed; it merely changes from one form to another. • When blowing a bubble into the air, a force acts upon it, causing it to fall to the floor. • The event is justified by evidence and an explanation.

  24. Aristotle (Greece, 4th Century BC) Philosopher who believed that: • There are 4 elements: earth, water, air, fire. • Matter is perpetually divisible.

  25. Democritus (Greece, 4th Century BC) • First atomic theory • Atom (indivisible).

  26. Alchemists (~300BC-1650 AD)China, India, Arabia, Europe, Egypt • Aiming to: • Change common metals to gold. • Develop medicines. • Developed lab equipment. • Mystical.

  27. Galileo Galilei (Italy 1564 AD) • Father of the scientificmethod (along with the Englishman Francis Bacon 1500’s).

  28. Antoine Lavoisier (France 1743-1794) • Regarded as the Father of Chemistry. • Designed equipment. • Used observations and measurements. • Discovered nitrogen.

  29. Dmitri Mendeléev (Russia, 1834-1907) • First Periodic Table of elements.

  30. Système Internationale d’Unitès Units • SI Units – International System • Basic Units Length (meter) m Mass (kilogram) kg Time (second) s Volume (liter) L • National Bureau of Standards

  31. Helpful Chart to remember Smaller Bigger deci (d) 1/10 deca (da) 10 centi (c) 1/100 hecto (h) 100 milli (m) 1/1000 kilo (k) 1000 micro (m) 1/1000000 mega (M) 1000000 nano (n) 1/ 1000000000 giga (G) 1000000000

  32. Derived Units • These units are derived by multiplying or dividing the base units. • Examples • Speed – m/s • Area – m2 • Volume – m3, but scientist tend to use the L or mL *1cm3 = 1mL • Density = g/mL (D=m/V)

  33. Accuracy vs. Precision • Accuracy – a description of how close a measurement is to the true value of the quantity measured • Precision – the exactness of a measurement

  34. Accuracy verses Precision

  35. Is it Accurate, Precise, Both or Neither? • Known Density = 3.11 g/mL • Test Results 3.77, 3.81, 3.76, 3.80 • Precise, not accurate • Test Results 3.01, 3.89, 3.50, 5.99 • Neither • Test Results 3.04, 3.20, 3.13, 3.07 • Accurate, not precise • Test Results 3.11, 3.12, 3.12, 3.10 • Both

  36. How do we represent error? • Error is the difference between the actual (or accepted) value and the experimental value • Percent Error Percent Error = Accepted – Experimental x100 Accepted

  37. Example Problem • Working in the laboratory, a student finds the density of a piece of pure aluminum to be 2.85 g/cm3.  The accepted value for the density of aluminum is 2.699 g/cm3.  What is the student's percent error?

  38. Solving Word Problems • Analyze • List knowns and unknowns. • Devise a plan. • Write the math equation to be used. • Calculate • If needed, rearrange the equation to solve for the unknown. • Substitute the knowns with units in the equation and express the answer with units. • Evaluate • Is the answer reasonable?

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