2. Objects and Properties

3. Objects : physical "things" in our environment Properties of objects –those qualities that make an object what it is Referent (reference) –how we view things due to our experiences –our window to the world –in physical science we need common referents (references) by which to study our physical universe

4. in science we need to eliminate vagueness in communication we do this by having standard measurements with which to make comparisons between objects A measurement consists of two parts: –numerical value: describes how big the measurement is –unit: tells us what the measurement is in; e.g., meters, kilograms, cubic centimeters, etc. the unit also shows the type of measurement we are making; e.g., length, mass, volume, etc.

5. Making a measurement A measurement consists of three activities: –choose a referent (reference), which will be your unit of measurement –compare the property you want to measure to the chosen reference (unit) –count the units (in the chosen reference)

6. Standard Units –in science a set of standard measuring units are used to ensure that measurements can be duplicated by others Two major systems of standard units: –Metric System Used throughout the world Based on powers of 10 –English System units which corresponded originally to parts of the human body

7. Many early units for measurement were originally based on the human body. Some of the units were later standardized by governments to become the basis of the English system of measurement.

8. Area (the size of a surface) can be described by two length measurements. Volume (the space an object occupies) can be described by three length measurements. Length, however, can be described only in terms of how it is measured, so it is called a fundamental property. Area and volume are called derived properties.

9. Fundamental (Base) and Derived Properties Fundamental (base) property –defined by itself, independent of other properties –Fundamental (base) properties are: length, mass, time, temperature, electric current Derived property –defined in terms of fundamental properties (depends on fundamental properties) –Examples: surface area, volume, speed (speed is distance divided by time), etc.

10. Metric system (MKS) - also called International System of Units (SI) Fundamental Properties Base Unit Symbol –Length meterm –Mass kilogramkg –Time seconds –TemperatureKelvinK –Electric currentampereA

11. Base Units for the Metric System Meter (m) –base unit of length: meter (m) 1m = 3.28 ft (foot is the base unit of length in the English system) Kilogram (kg) –base unit of mass: kilogram (kg) Mass represents the amount of matter (substance) contained in an object. The mass of an object is a measure of the inertia (resistance to movement) of that object. Weight is the effect of gravity on an object. The weight of an object changes with location, the mass of an object does not. Second (s) –base unit of time: second (s) (also the base unit of time in the English system)

12. Each of the base units in the metric system can be modified with different prefixes which multiply out the base unit by some factor Prefix Symbol Meaning GigaG1,000,000,000 times the base unit MegaM1,000,000 times the base unit Kilok1,000 times the base unit Hectoh100 times the base unit Dekada10 times the base unit Decid0.1 of the base unit Centic0.01 of the base unit Millim0.001 of the base unit Micro  0.000001 of the base unit Nanon0.000000001 of the base unit

13. The Scientific Method Method for developing scientific knowledge Steps: –Hypothesis: possible explanation of a phenomenon –Experiments: test the hypothesis If the hypothesis fails, revise it and retest If the hypothesis passes, more experiments for more testing and greater confidence –An accepted hypothesis may result in a scientific principle or in a scientific law Scientific principle An explanation concerned with a specific range of phenomena Scientific law Describes a more general and important phenomenon than a principle Expressed: –in verbal form –by an equation –by a graph

14. Scientific Models and Theories Model –simulation of a real object or phenomenon –used to study something that cannot be observed directly physical model - can be seen and touched mental model - exists in the mind and helps us understand concepts equation model - describes the variables involved and their relationship Theory –a broad, detailed explanation of a phenomenon –Hypothesis: statement before tests –Theory: has passed the test

15. Scientific Statements and Data Must be testable (measurable) Data (or measurements) must meet two criteria: –Reliability everyone agrees to the meaning of the data (measurements) others can replicate the measurements (or the experiments) with the same results –Precision Repeatable and reproducible measurements that conform to standards