Identifying Variables &Identifying Variables &Designing Designing

InvestigationsInvestigationsin the Scientific in the Scientific

Method.Method.Environmental ScienceEnvironmental Science

3 Kinds of Variables in 3 Kinds of Variables in Environmental ScienceEnvironmental Science

Independent Variable – something that is Independent Variable – something that is changed by the scientistchanged by the scientist What is testedWhat is tested What is manipulatedWhat is manipulated What is controlledWhat is controlled Example: The more concentration of Carbon Example: The more concentration of Carbon

dioxide – the higher temperature in the dioxide – the higher temperature in the atmosphereatmosphere

Something else?Something else?

3 Kinds of Variables in 3 Kinds of Variables in Environmental scienceEnvironmental science

Dependent Variable – something that Dependent Variable – something that might be affected by the change in might be affected by the change in the independent variablethe independent variable What is observedWhat is observed What is measuredWhat is measured The data collected during the The data collected during the

investigationinvestigation

3 Kinds of Variables in 3 Kinds of Variables in Environmental scienceEnvironmental science

Controlled Variable – a variable that Controlled Variable – a variable that is not changedis not changed Also called constantsAlso called constants Allow for a “fair test”Allow for a “fair test” Any example we know in Environmental Any example we know in Environmental

Science?Science? Any other law?Any other law?

Let’s look for several exa- Let’s look for several exa- mples for Environmental mples for Environmental

ScienceScience

First Example we have isFirst Example we have isin Environmental science:in Environmental science:

Concentration of carbon Concentration of carbon dioxide is the independent dioxide is the independent

variable.variable.Measured temperature is Measured temperature is

dependent variable. dependent variable.

Now remember the very Now remember the very important step in our important step in our

investigation!investigation!Let’s identify the variables Let’s identify the variables

in this investigation.in this investigation.

What was the independent What was the independent variable?variable?

Concentration of carbon dioxideConcentration of carbon dioxideDifferent concentrations were Different concentrations were

tested by the scientisttested by the scientistRemember that temperature was Remember that temperature was

fixed and thus constant!fixed and thus constant!So what is changing? ????So what is changing? ????

What was the dependent variable?What was the dependent variable?

The temperatureThe temperatureThe temperature was observed The temperature was observed

and measured by the scientistand measured by the scientist

Actually, the dependence is linearActually, the dependence is linear And we have to investigate it!And we have to investigate it!

Are you getting the idea?Are you getting the idea?Or not!?!Or not!?!

Another example in the Another example in the Environmental Science:Environmental Science:

An investigation was done with a An investigation was done with a closed water - fish system made closed water - fish system made

from a closed container - from a closed container - aquarium. Different aquarium. Different

concentration of salt was used in concentration of salt was used in the water. The growth of fish was the water. The growth of fish was

checked by their size.checked by their size.

What are the variables in this What are the variables in this investigation?investigation?

Just be careful!Just be careful!But give your opinions!?But give your opinions!?

Go!Go!Please!Please!

Can we do it!?Can we do it!?

Independent variable in Independent variable in Environmental Science:Environmental Science:

Concentration of salt. Why?Concentration of salt. Why?Just because -Just because -

These concentrations were These concentrations were changed by the scientist. He changed by the scientist. He can pick up anything he likes! can pick up anything he likes!

Can he?!Can he?!

Dependent variable:Dependent variable:

Size of fishSize of fishOf course we have more Of course we have more

parameters to consider!parameters to consider!

What is your answer?What is your answer?

Controlled variables:Controlled variables:

Devices to measure Devices to measure parametersparameters None of these items were changedNone of these items were changed

REMEMBER WHAT IS UNDER CONTROL?REMEMBER WHAT IS UNDER CONTROL?

WHAT ELSE IS NOT CHANGING?WHAT ELSE IS NOT CHANGING?

Let’s go to one more Let’s go to one more example in Environmental example in Environmental

science!science!

The higher the The higher the temperature of water, temperature of water, the faster an egg will the faster an egg will

boil?!boil?!ARE YOU SURE ARE YOU SURE ABOUT THAT?ABOUT THAT?

SHALL WE CHECK?SHALL WE CHECK?

WHAT WE HAVE IN THIS WHAT WE HAVE IN THIS INVESTIGATION?INVESTIGATION?

Let’s see:Let’s see: Independent variable – temperature Independent variable – temperature

of waterof water Dependent variable – time to cook Dependent variable – time to cook

an eggan egg Controlled variable – type of eggControlled variable – type of egg

Last example for today in Last example for today in Environmental Science:Environmental Science:Remember the previous Remember the previous

examples?!examples?!What did you get from What did you get from

those examples?!those examples?!Any idea?!Any idea?!

The temperature of The temperature of water was measured at water was measured at

different depths of a different depths of a pond.pond.

LET’S SUMMARIZE OUR LET’S SUMMARIZE OUR RESULTS:RESULTS:

Independent variable – depth of the Independent variable – depth of the waterwater

Dependent variable – temperatureDependent variable – temperature Controlled variable – thermometerControlled variable – thermometer

We are designing InvestigationsWe are designing Investigations

Basically we plan and do the Basically we plan and do the steps of work to accomplish our steps of work to accomplish our

final goal!final goal!Which was what?!Which was what?!

Now do you see how all is Now do you see how all is connected and important?!connected and important?!

The greater the amount of soap in a The greater the amount of soap in a soap and water mixture, the bigger a soap and water mixture, the bigger a

soap bubble can be blown.soap bubble can be blown. Design an investigation to test this Design an investigation to test this

hypothesis.hypothesis. Identify the variablesIdentify the variables What exactly will be changed? How will it What exactly will be changed? How will it

be changed?be changed? What exactly will be measured? How will What exactly will be measured? How will

it be measured?it be measured? WRITE IT AS A HOMEWORK!WRITE IT AS A HOMEWORK!

The farther a ball drops, the higher The farther a ball drops, the higher it will bounce.it will bounce.

Design an investigation to test this Design an investigation to test this hypothesis.hypothesis. Identify the variablesIdentify the variables What exactly will be changed? How What exactly will be changed? How

will it be changed?will it be changed? What exactly will be measured? How What exactly will be measured? How

will it be measured?will it be measured? WRITE IT AS A HOMEWORK !WRITE IT AS A HOMEWORK !