ChemPhys, Chapter 1

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Chapter 1 The Nature of Science
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What is Science?

• Science is a method for studying the natural
  world. It is a process that uses observation and
  investigation to gain knowledge about events in
  nature.
• Scientific explanations help you understand the
  natural world.
• Example Heat is the vibration of particles in a
  substance not an invisible fluid (as thought in
  the 18th century).

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Main Categories of Science

• Life science (biology) deals with living things
• Earth science investigates Earth and space
• Physical science (chemistry and physics) deals
  with matter and energy

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Investigations

• Observing something occur (record observations in
  a journal)
• Set up an experiment to test something
• Build a model of something that occurs in nature
  and then test the model to see how it reacts.

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Question

• Why do scientific explanations change?

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Scientific Method

• The scientific method is an organized set of
  steps used to study an event in nature.
• It consists of six general steps. (Next slide).

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Scientific Method

• State the problem
• Gather information
• Form a hypothesis
• Test the hypothesis
• Analyze data
• Draw Conclusions

hypothesis supported
Hypothesis not supported
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Stating a Problem

• A statement of a person who wonders how or
  why something occurs.
• Examples
• Why does a ball fall to earth when released?
• How does my i-Pod work?

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Gathering Information

• What is already known about the problem?
• Library?
• Experts?

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Hypothesis and Experiment

• A hypothesis is a proposed explanation.
• An experiment is a way of testing a hypothesis
  under controlled conditions.

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Variables

• A variable is a measurable quantity that can have
  more than a single value.
• An independent variable is controlled by the
  scientist to see what the effect will be.
• A dependent variable has a value which depends on
  values of the other variables in the system.

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Constants and Controls

• A factor that does not change when other
  variables change is called a constant.
• A control is a standard by which other test
  results can be compared.
• Question Why is a control used in an experiment?

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Analyzing Data, Drawing Conclusions

• Analyzing Data - All data must be recorded and
  organized.
• Drawing Conclusions - Based on the analysis of
  the data, you decide whether or not your
  hypothesis is supported.
• If not Form a new hypothesis
• If so Continue to test the hypothesis

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Being Objective

• Scientists must try to record the observations
  just as they are and not let what they expect
  affect the recorded data.
• Bias occurs when what the scientist expects
  changes how the results are viewed.

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Models

• A model represents an idea, event, or object to
  help people better understand it.
• Examples
• Globe
• House plans
• Model airplane
• Toy train

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Theories and Laws

• A scientific theory is an explanation of things
  or events based on many observations and
  investigations.
• A scientific law describes what will happen in
  nature and seems to be true all the time. A law
  explains what will happen under certain
  conditions but does not explain why or how it
  happens.

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Technology

• Technology is the application of science to solve
  problems and help people.
• Examples
• Wide screen TV
• Antibiotics
• Cell phones
• Photocopiers

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Chapter 1, Section 1 Review

• What are the steps that scientists often use to
  solve problems?
• Why do scientists use variables?
• What are the similarities and differences between
  science and technology?

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Standards

• A standard is an exact quantity that people agree
  to use to compare measurements.
• Examples
• Time - Atomic clock
• Length - distance light travels in a precise time
  interval.

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SI Base Units
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Common SI Prefixes
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Question

• How many meters in a kilometer?

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Factor Label Method

• Express 4.5 kg as grams
• Begin by Expressing as a Fraction 4.5 kg
  1
• Identify Conversion Factor 1 kg 1000 grams
• Express as a Fraction

1 kg 1000 g 1
--------------- or --------------
1000 g 1 kg
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Factor LabelContinued

• Write Equation Including Proper Factor
• Cancel Units
• Multiply Numbers to Get Final Result

4.5 kg 1000 g --------- x
-------------- 4500 g 1 1
kg
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Factor Label Steps

• Express as a Fraction
• Identify Conversion Factor
• Express Conversion Factor as Two Fractions
• Select Proper Factor (units in denom.)
• Write Equation Including Proper Factor
• Cancel Units
• Multiply Numbers to Get Final Result

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Volume

• The amount of space occupied by an object is call
  its volume.
• Volume length x width x height
• Units length cubed
• cm3
• M3
• 1 cm3 1 mL (1 milliliter)

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Density

• Mass is the quantity of mater in an object (SI
  unit kg).
• Density is the mass of an object divided by the
  volume of the object. (g/cm3)
• Density is an example of derived units obtained
  by combining different SI units.

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Temperature

• Temperature is usually measured using the Celsius
  scale.
• 0o Celsius freezing point of water
• 100o Celsius boiling point of water
• 1 degree Celsius 1 degree Kelvin
• 0 kelvin -273o Celsius
• 0o Celsius 273 kelvin
• 100o Celsius 373 kelvin

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Chapter 1, Section 2 Review

• Name the prefixes in the SI system and the
  multiple of ten that each represents.
• Identify the SI units and symbols for length,
  volume, mass, density, time, and temperature.
• How are SI units converted from one to another?
  (Describe the factor label method.)

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Graphs

• A graph is a visual display of information or
  data.
• Three Types of Graphs
• Line Graph
• Bar Graph
• Circle Graph

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Line Graph

• A line graph shows the relationship between an
  independent variable (on the x axis) and a
  dependent variable (on the y axis).
• You can show more than one event on the same
  graph.

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Room Temperature Data
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Classroom Temperature
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Bar Graphs

• A bar graph is useful for comparing information
  collected by counting.

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Classroom Size Data
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• 21 22 23 24 25 26 27
• Students

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Circle Graphs

• Circle Graphs are used to show how some fixed
  quantity is broken down into parts.

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Chapter 1, Section 3 Review

• Identify three types of graphs.
• Explain the ways that each type of graph is used.
• How can data be analyzed or compared on a graph?