Defining Physical Science

Transcription

1 Defining Physical Science Physical Science is the study of matter & energy; a merging of two major branches of science: 1. Chemistry - study of the composition & changes of matter, 2. Physics - study of energy & laws of motion (i.e. the behavior of matter).

2 Advances in Physical Science Advances first stem from a need, followed by inquiry. Science is the investigation of rational concepts capable of being tested by observations and experimentation; this analytical method distinguishes science from all other disciplines. If something is not testable, it is philosophy, not science. Scientists Question natural phenomenon, Observe the world among them, Read a variety of scientific books, Become science teachers. You are a scientist if you do any of these!

3 Basic assumptions of science: 1. There is order in the universe. 2. The human mind is capable of understanding it. 3. Natural phenomenon is testable by experimentation that is repeatable. A real scientist will attempt to answer their questions. The scientific method - a systematic approach to problem solving 1. State the problem Must first define the problem based on observation of a need. 2. Gather information on the problem Leave no stones unturned - the problem may already be solved, at least partially. 3. Form a hypothesis A hypothesis is a plausible prediction of the experimental results.

4 This serves to focus the experiment and to prevent bias. It is not faulty science if your hypothesis is determined wrong. Sometimes our findings defy our current reasoning. Use deductive reasoning (if/then statement). E.g. If I use a fuel additive in my car, then it should improve the cars mileage. A hypothesis is often stated as a question. E.g. Will I float if I m on the Moon?

5 4. Experiment - test the hypothesis. The variable is the factor being tested. The data (datum singular) is the information outcome of the experiment. Types of data: Quantitative data - numerical data Qualitative data - descriptive data (color, behavior, etc.) Must use a control setup & experimental setup. The experimental setup contains the variable to be tested; the control does not. The control is the standard for comparison. 5. Record & analyze data Use accurate measurements. In most cases the metric system of measurements is the most accurate.

6 6. State conclusion Only after the experiment has been repeated to insure accuracy. If a hypothesis withstands repeated testing, a theory is developed. A scientific theory is the most logical explanation of events occurring in nature. A theory that withstands repeated testing may become a scientific law. A scientific law is generally accepted as true, but may be modified after further discoveries. Be careful! It may well be that some of what we hold as scientific truth may be wrong from its inception, and problems become amplified as you extend farther from a flawed foundation.

7 A fact is the absolute truth. Scientific method in practice 1. The problem We need to lower the freezing point of H 2 O to -10 o C. 2. Information on the problem 3. Hypothesis H 2 O freezes at 0 o C. Ethylene glycol freezes at -30 o C. One part ethylene glycol to 10 parts H 2 O will lower the freezing point to -10 o C. 4. Experiment Set up 6 replications of 1:10 ethylene glycol mixtures and 6 H 2 O control setups, and then decrease temperature.

8 5. Record & analyze data Control H 2 O o C Experiment H 2 O w/ 1 / 10 ethylene glycol _ 0_ -2 X = 0-3 o C 6. Conclusion The freezing point of H 2 O w/ 1 / 10 ethylene glycol is -3 o C. Caution! Never test more than one variable at a time.

9 Temperature (C) Use graphs to ease in interpreting data o Time of freezing of H 2 O w/ 1 / 10 ethylene glycol (antifreeze). Time (min) Temp o C_ Temp Time (min)

10 Spaces between intervals on a graph must be equal. Scientific Terms Does this graph represent the control or experimental setup? Review common prefixes & suffixes on page 18 Figure 1.14 What does converge mean? A. Come together How would the temperature of a reacting substance be affected in an endothermic reaction? Temperature would go up (opposite of exothermic).

11 Scientific Measurements Measurements must be accurate, reliable, & appropriate to the subject measured. Scientists use the metric or ISU system (International System of Units). Measurements Basic units Length meter (m) Volume liter (L) Mass kilogram (kg) Weight Newton (N) Density gram/liter (g/l) Temperature Celsius ( o C) Metric Prefixes Kilo (k) = 1000 or 10 3 Hecto (h) = 100 or 10 2 Deka (dk) = 10 or 10 1 Deci (d) = 0.1 or 10-1 or 1/10 Centi (c) = 0.01 or 10-2 or 1/100 Milli (m) = or 10-3 or 1/1,000 Micro ( ) = or 10-6 or 1/1,000,000

12 Length measure of distance 1 meter = 39.4 inches (~1yard) = 100 centimeters = 1000 millimeters 1000 m = 1 kilometer Volume amount of space an object takes up Basic unit = Liter (L) or cubic centimeter (cc or cm 3 ) 1cm 3 = 1 milliliter (1/1000 liter) Liters are usually used to measure fluid volume. Cubic centimeter is usually used to measure solids. E.g. the volume of a box can be measured by: Length x width x height How could you measure the volume of an irregular shaped object in liters? Make use of Archimedes principle water displacement.

13 Liquid volume is measured using a graduated cylinder. Measurements are read at the bottom of the meniscus (curved surface). Mass the amount of matter in an object Basic unit = kilogram (1000 grams) Mass is measured using a triplebeam balance Note: mass is not the same as weight. Density the amount of mass in a given volume of an object Density may be affected by: 1. Space in an object, and/or 2. Temperature of an object.

14 Density = mass per volume of a substance calculated by: D= M/V Where: D = density M = mass V = volume Water density = 1g/ml If wood floats in water, is its density greater than or less than one? Temperature the amount of heat in an object Basic unit = Celsius ( o C) 0 o C = freezing point of water 100 o C = boiling point of water Body temperature = 37 o C Room temperature = 21 o C

15 Dimensional Analysis method of converting one unit to another. Dimensional analysis uses a conversion factor a factor that always equals one. E.g 1000 grams / 1 kilogram = 1 or, 1kilogram / 1000 grams = 1

16 Problem convert 1350 grams to kilograms Conversion factor 1350 g X 1 kg = 1350 kg = 1.35 kg g 1000 Cancel the grams, multiply, and reduce.

17 Important laboratory safety rules Never do anything until you are instructed. Wear safety glasses in the lab when you, 1. Use fire of any kind, 2. Handle hot glass, 3. Measure, mix, or pour chemicals. Think before you act.