UNIT: Chemistry and Measurement

Objectives: Lesson 1 of 4• You will learn the importance of chemistry and the problem solving

nature of Science• You will understand the scientific method and the steps involved• You will be able to distinguish between a scientific Hypothesis,

Theory, and Law• You will become familiar with some basic terms and principles of lab

investigation, such as dependent, independent, and control variables

TOPIC: Chemistry and the Nature of Science

QuickwriteIn 1-2 sentences answer one of the questions below:• What sort of things come to mind when you think of

Chemistry?• How do you think Chemistry has improved our lives?

The Importance of Chemistry• Everything around us is chemistry: The air we breathe, the coins

in our pocket, the material that makes up our electronic devices, the medicine in our medicine cabinets

• Look around, it’s all chemistry, or matter!• Studying Chemistry is important, it allows us to solve many of

the worlds problems, everything from environmental issues to new medicines that treat cancer and other ailments

• Chemistry is defined as the science that deals with the materials of the universe (matter) and the changes that these materials undergo

What is Chemistry?• The science that deals with the materials

of the universe (matter) and the changes that these materials undergo

Chemistry and the Scientific Method• Science and Chemistry is about solving problems• To solve problems, scientists use something

called the scientific method• The scientific method is a systematic process

that utilizes a series of inquiry based steps and observations about or natural world

What is the scientific method?• A systematic process that utilizes a series of

inquiry based steps, observations, and measurements about or natural world

15.5 grams

Steps in the Scientific Method1. State the problem and make qualitative or

quantitative observations– Qualitative observations involve a physical description

(the quarter is shiny or lustrous)– Quantitative observations involve

a quantity or measurement (the quarter weighs 15.5 grams)

Steps in the Scientific Method2. Formulate a hypothesis; a hypothesis is an idea or

explanation based on observations3. Perform experiments; an experiment is something

we do to test the hypothesisThe data/information we gather during the experiment allows us to decide whether to accept or reject our hypothesis

4. Iterate or repeat experiments to confirm results

What steps makeup the scientific method?1. State the problem and make qualitative (physical) and

quantitative (measurement) observations2. Formulate a hypothesis, an idea based on observations3. Perform experiments that produce data and

information allowing you to either accept or reject your hypothesis

4. If necessary, repeat experiment to confirm results

Hypotheses, Theory and Law• Recall that a Hypothesis is an idea based on observations that has yet to be

proven• Once a hypothesis has been confirmed through repeated experiments that

consistently arrive at the same conclusion, we can begin to develop a scientific theory

• A scientific theory is an idea(s) or explanation for some phenomenon that is based on and supported by evidence through observation, experimentation, and reasoning

• It is different from a hypothesis in that it is supported with experimental evidence

• Theories attempt to explain our natural world and can be further refined through additional experiments

• A scientific law is a descriptive generalization about how some aspect of the natural world behaves under stated circumstances

• It is a readily observable fact about something and is often confirmed true by a mathematical expression such as E = mc2

• Both laws and theories are supported by experiments and empirical data

• However, a law seeks to describe a natural action under a given set of conditions, and a theory explains how and why something happens

Hypotheses, Theory and Law

• For example, consider the Ideal Gas Law, PV = nRT• This mathematical expression describes and makes

generalizations about the behavior of gas molecules in our natural world under a given set of conditions

• On the other hand, consider the Big Bang Theory, it seeks to explain the origin of our universe through ideas that have been supported through scientific research studies and evidence

• Both a scientific theory and law are accepted to be true by the scientific community

Hypotheses, Theory and Law

In science, what is the difference between a Hypothesis, Theory and Law?

• A hypothesis is an idea based on observations that has yet to be proven

• A theory is an idea(s) or explanation for some phenomenon that is supported by evidence through observation, experimentation, and reasoning

• A law is a descriptive generalization about how some aspect of the natural world behaves under stated conditions

• Both a theory and a law are supported by experiments

Experimental Design• In every experiment we have what are called

variables• Variables may change or not change at all• A variable is any factor or condition such as

temperature, volume, or mass that can change or remain constant in an experiment

• An experiment has 3 kinds of variables: independent, dependent, and controlled.

What is a Variable?• Any factor or condition such as temperature,

volume, or mass that can change or remain constant in an experiment

• 3 types: independent, dependent, or control

Independent, Dependent and Control Variables• In an experiment we have what are called variables• The independent variable is the variable that you (the person doing

the experiment) change or manipulate in the experiment for a desired outcome or effect

• It may be temperature, pressure, or the amount of chemical available• The dependent variable is the variable that changes as a result of the

independent variable; and is the variable being tested in an experiment

• Control variables are variables that are kept constant to improve the accuracy of your experiment

Independent, Dependent and Control Variables• Let’s say you want compare the cleaning effectiveness of

chemical brands X and Y on their ability to remove grass stains on clothing

• In this experiment, there are many variables that could effect the outcome of your experiment, the amount of cleaning chemical, the size of the stain, the type of clothing

• The independent variable, the variable you manipulated in this case would be the type of cleaning chemical (X or Y)

• The dependent variable would be how well each stain was removed and eliminated from the clothing (it is dependent on the independent variable)

• Controlled variables consisted of equal amounts of cleaner, same types of clothing, and the same stain size,

• For accuracy, these control variables remained constant throughout the experiment

X Y

What is the difference between an independent, dependent, and control variable?• The independent variable is the variable that is changed or

manipulated in the experiment for a desired outcome • The dependent variable is the variable that changes as a

result of the independent variable; it is the variable being tested in an experiment

• Control variables are variables that are kept constant to improve the accuracy of your experiment

Summary (you can always write your own summary)

• Explain the science of Chemistry in your own words• Condense the scientific method into one sentence• Make a Venn diagram relates scientific law and scientific theory

• Design a your own simple experiment and identify any independent variables, dependent variables, and control variables

Law Theory

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