Benchmark Lesson 1

AUTHOR: Sumana Islam

GRADE LEVEL: High School Science.

TIME: 50 minutes.

TEKS:

The student is expected to:

-Demonstrate safe practices during field and laboratory

-Plan and implement investigative procedures including asking questions, formulating testable hypotheses, and selecting and using equipment and technology.

- Collect data by observing and measuring.

- Communicate valid conclusions.

-Identify and describe the greenhouse effect.

-Understand that the greenhouse effect leads to global warming.

CONCEPT(S):

The students will simulate greenhouse effect in a jar. They will use temperature probes to measure temperatures in a model greenhouse (closed jar) and a control (open jar) as the jars get heat up using solar energy. They will then calculate the resulting temperature changes.

OBJECTIVES (LEARNER OUTCOMES):

Students will be able to:

i) understand how greenhouses help plants to survive in a cold weather. They will further know that the Earth warms up in a similar fashion.

ii) perform a laboratory analysis to create a model greenhouse and compare temperature changes in the greenhouse model with the outside temperature.

iii) think that ‘greenhouse effect in earth’ is a good process which enables us to survive, but at the same time think ahead what might happen if the warming process continues to go up.

MATERIALS LIST: for a class of 24 working in pairs.

12 large glass jars of the same size

24 outdoor thermometers

small pieces of thin cardboard tape

clear plastic wrap

rubber bands or string

watch or clock

graph paper

straightedge or ruler

notebook

pen or pencil

ADVANCED PREPARATIONS: fixing the thermometers in the glass jars.

SAFETY: none.

SUPPLEMENTARY MATERIALS: data table and evaluation question sheet.

RESOURCES: Environmental Science, 1996, by Karen Arms and internet source

http://commtechlab.msu.edu/sites/letsnet/noframes/subjects/science/b5u1l3.html

ENGAGEMENT

Time: ___7 minutes__

What the Teacher Will Do	Eliciting Questions	Student Responses
	Did you ever try growing plants outside in freezing winter temperature?	No/ Yes.
	When we grow plants or vegetables in our backyard, do they survive in the freezing temperature?	No. They freeze and die.
	Can you tell me an arrangement where plants are living well even when outside temperature is very low?	Various response, with one or two of them might answer right. In a greenhouse.
	Good!
Explain greenhouse which is simply a house made of glass through which sun light can get inside easily. But some of the light energy (infrared) can not pass through the glass and stays inside and keeps the glass house warm.	So you can understand that greenhouse is helping the plants survive in cold temperature.
	Can you imagine earth as a giant greenhouse?	May be. No.
Our earth is covered by a layer of atmosphere which acts similar to the glass jar. This effect is called “greenhouse effect”. Today we are going to construct a “greenhouse” in a jar to model the warming of earth.

EXPLORATION

Time: _20 minutes____

Describe them the procedure which is………. attaching thin pieces of cardboard over the bulbs of two weather thermometers. Then place one thermometer in each of two jars, tapping them inside of the jars so that they are not touching the bottoms. Cover the opening of one jar with plastic wrap and secure it with a rubber band.

What the Teacher Will Do	Eliciting Questions	Student Responses
	Which of the two jars is the greenhouse model?	The covered jar.
	Which one is the control? What is the purpose of the control?	The opened jar. You need to compare with a same condition of arrangement, except a variable in order to know the effect of the variable.
	What is the variable in this experiment?	The covering of the jar.

Before starting the experiment, make a table similar to the one shown below.

Data table for greenhouse model
time	temperature
	Uncovered jar (control)	Covered jar (“greenhouse” jar)
Before going outside
When first placed in sun
+ 2 minutes
+ 4 minutes
+ 6 minutes
+ 8 minutes
And so on ---

Take the jars outside and place them in a bright sunny spot. Take readings of the thermometers every 2 minutes and write it on the chart. Continue for 10 minutes or more until the temperatures increases noticeably in both jars. Make a line graph that shows the result.

EXPLANATION

Time: __7 minutes___

What the Teacher Will Do	Eliciting Questions	Student Responses
After taking readings and making graphs..	Do you see any difference in readings between covered and uncovered jar?	Yes we see a difference.
	What kind of difference do you see?	The temperature in the covered jar increased with time, but the uncovered jar had little effect due to exposure of the sun.
	Can you explain why?	The covered jar is closed, that’s why.
Very good! The air inside the uncovered jar can move and as it gets warm it is replaced by cooled air. On the other hand, the air inside the covered jar is trapped and cannot move. So it takes energy from sunlight and gets warmer and warmer.

Tell them that a similar trapping of heat happens in the Earth’s atmosphere. Sunlight passes through the atmosphere and warms the Earth’s surface. The heat radiating from the surface is trapped by greenhouse gases. Both the atmosphere and the jar allow light to enter, but then trap that energy which is then converted to heat. However, they work differently, because the jar keeps in the heated air, while the greenhouse gases absorb radiated heat.

ELABORATION

Time: __4 minutes___

What the Teacher Will Do	Eliciting Questions	Student Responses
Now you know what “greenhouse effect” is and that it is normally a good thing.	Can you imagine how much the temperature of earth could be without this greenhouse effect?	The planet would probably be too cold to live.
Tell them that without the greenhouse effect, the average temperature of the earth would be about 33^oC or 60^oF lower.
	Now what if the warming process is going up for some reason, do you think it is a concern?	May be it will be too hot eventually.
	Any other effect?	Do not know.
Tell them that we will continue with this thought to our next lesson. Finish with the following thought…	Just think if a glass full of water with one or two pieces of ice is left outside, what happens when the ice melts?	Water flows over the glass.

EVALUATION

Time: _7 minutes___

1) Define greenhouse and greenhouse effect.

2) Mark which one is correct:

i) Greenhouse gases are keeping the Earth surface cooler.

ii) Greenhouse gases are keeping the Earth surface warmer.

iii) Greenhouse gases are keeping the Earth surface temperature same.

3) Draw picture and explain how the Earth acts as a giant greenhouse.

4) What do you predict if earth’s temperature continues to go higher?