Name:______
ABSORPTION
STATION
What to do…
Step1:Start Lab 9.1: Black Can VS. Shiny Can. DO NOT forget units.
Step2: Read article “How it Happens: The Physics Behind the Urban Heat Island. Pull out 5 key words from the article.
Step 3: Give the gist (a brief summary) of the article.Here is the hard part; you can only use 20 words.
Step 4: Complete the Regents Questions, move back to your Desk Station and if you require extra time.
How it Happens: The Physics Behind the Urban Heat Island Effect
By Jane McGrath at howstuffworks.com
To understand the urban heat island effect, we first should understand that objects can absorb and reflect light. In fact, the color of an object depends on what kind of light it reflects. For example, a green object reflects green light and absorbs all the other visible colors of light. When we see a green object, we perceive it as green because it reflects the green wavelength of color back to our eyes. Darker colored objects are excellent absorbers of light. In fact, black surfaces absorb almost all light. On the other hand, lighter colored surfaces do not absorb much light at all -- rather they reflect almost all of it.
So what does the absorption of light have to do with heat? When an object absorbs light, it converts that light to thermal energy, and emits it back out as heat. So, because black objects absorb more light, they also emit more heat. That's why wearing a black shirt on a hot, sunny day will only make you hotter. The black shirt absorbs light and emits it as heat onto your skin. Wearing a white shirt, on the other hand, will help reflect the sunlight and keep you cooler.
The rate at which an object can reflect solar radiation is called its albedo. The bigger the albedo something has, the better it reflects radiation. Traditional asphalt has a low albedo, which means it reflects radiation poorly and instead absorbs it.
When we build and expand cities, we build buildings with dark surfaces and lay down asphalt pavement. The buildings and the pavement absorb a significant amount of light and radiation and emit it as heat, warming the city. Because more than half of the surfaces in cities are man-made, with asphalt and concrete, cities heat up more than rural areas. Cities hold on to more heat for a longer period of time than rural areas do. This is called the Urban Heat Island Effect.
But that's not the only thing that causes the urban heat island effect. Scientists believe that vegetation plays a large part in keeping an area cool through a process called evaporative cooling. Evaporation is when liquid turns into gas. Plants take in water through their roots and depend on it to live. But after the plant is done with it, dry air absorbs that water by turning it into gaseous water vapor. The air provides the heat that drives this process, so during the process, the air loses heat and becomes cooler. We experience the same type of thing when we sweat -- when air hits your sweaty skin, it absorbs the moisture and cools the air around you. Because building a city means replacing vegetation with structures, the city loses the evaporative cooling advantages of vegetation.
Other factors also contribute to the effect. For instance, cars and air conditioners, which are abundant in urban areas, convert energy to heat and release this heat into the air.McGrath, Jane. "What is the urban heat island effect?" 29 April 2008. HowStuffWorks.com. < 26 March 2014.
Name: ______
Key Words
1. ______
2. ______
3. ______
4. ______
5. ______
The Gist
Article Name:______
Author Name:______
Remember a gist can only be 20 words; make them count! Also, you must use the 5 key words you picked out.
______
Laboratory Activity 9.1 / Black Can / Shiny Can / [40]Introduction:
Did you ever wonder why in the summer light colored clothes are more popular and in the winter dark clothes are more popular. Well, you may find out that it is more than a fashion statement. Different surfaces absorb and radiate heat differently. Can you figure out which color absorbs and radiates heat more?
Objective:
Determine how the color of a material affects energy transfer byradiation
Procedure:
1.Arrange the black and white (shiny) cans as shown in thediagram.
2.Center both cans 8 inches in front of thelamp.
3.Record the temperature of each thermometer at Time 0 in the data tableprovided.
4.Turn on the lamp and read the thermometers at one minute intervals for 10 minutes. Record these temperature readings in the data tableprovided.
5.Without disturbing the positions of the cans, turn off the lamp and turn it away from the area of the cans. CONTINUE TO TAKEREADINGS
6.Continue taking temperature readings every minute foranother 10 minutes recording them on the data tableprovided.
7.Create a line graph using your data. Plot both curves on the same set of axes. Remember to label the graph and use akey.
Data Table
Time (min) / 0 / 1 / 2 / 3 / 4 / 5 / 6 / 7 / 8 / 9 / 10Temp (˚C) / Black
Shiny
Without disturbing the positions of the cans, turn off the lamp after 10 minutes and turn it away from the area of the cans. CONTINUE TO TAKE READINGS
Time (min) / 11 / 12 / 13 / 14 / 15 / 16 / 17 / 18 / 19 / 20Temp (˚C) / Black
Shiny
line Graph for Black and Shiny Can
Check Point
1.Why was it important to place each can an equal distance from the lamp? ______
2. Which can received the most energy, black or shiny can? ______
3. After 10 minutes why was it necessary to turn the lamps away from the area of the cans? What does this represent? ______
4. (a) Which can absorbed energy more quickly, shiny or black can? ______(b) Describe how your graph illustrate this. ______
5. (a) Which can radiated energy more quickly?______
(b) How does your graph illustrate this?______
6. Which can had the greatest rate of change throughout this experiment? ______
7. What evidence can you find from your graph that indicates neither cup heated up nor
cooled off at a constant rate? ______8. If you know that the surface is a good absorber of energy, what can you infer about its
ability to radiate energy? ______
9. What characteristic of the surface was tested in this lab to determine the rates of heatingand cooling? ______
A good absorber of electromagnetic energy is
a good radiator of electromagnetic energy.
- Write the statement above on the lines below.
______
If a material heats up fast, it also cools down fast.
- Write the statement above on the lines below.
______
Absorption of radiation: Dark vs. Light
Write the following information on the corresponding lines in the diagram below.
-Absorbsgreatestamountofheat-Reflectsthegreatestamountheat / -Radiatesthegreatestamountofheat
-Radiatestheleastamountofheat
Absorption of radiation: Smooth vs. Rough
Write the following information on the corresponding lines in the diagram below.
-lesssurfacearea–doesnotabsorbasmuch / -more reflection lessabsorption
-less reflection moreabsorption
Regents Questions:
1.A person in New York State worked outdoors in sunlight for several hours on a day inJuly.
Which type of clothing should the person have worn to absorb the least electromagnetic radiation?
(1)dark colored with aroughsurface(3) dark colored with a smoothsurface
(2)light colored with aroughsurface(4) light colored with a smoothsurface
2.The diagram to the right shows a light source thathasbeen heating two metal containers of air for 10 minutes. Both cups are made of the same material and are equal distances from the light source. Compared to the amount of energy reflected by the shiny cup during the 10 minutes of heating, the amount of energy reflected by the black cupis
(1)less(2)greater(3) thesame
3.Which type of land surface would probably reflect the most incoming solarradiation?
(1)light coloredandsmooth(3) light colored andrough
(2)dark coloredandsmooth(4) dark colored andrough
4.Which of the following Earth surfaces usually reflects the most incoming solarradiation?
(1)snowcover(2) darksoil(3)greengrass(4) lakewater