各位英语好手来看看Ah Lai's EggSomeone gave Ah Lai an egg.He was very happy."I shall not eat it," he thought."I shall keep it.I shall keep it in my pocket.It will be warm there.Soon it will become a chicken.T eggs will become a hen.The hen will give me more eggs will become chickens and they will become hens.The hens will give me more eggs.I shall sell them.I shall be a rich man.Ishall have many bags of gold.I shall live in a big house.The house will have gold door andwindows.It will be very big."Then Ah Lai dropped the egg."Now I shall not be rich,"he thought."I'masilly boy." He was sad.
固始县34kgAL
阿来的鸡蛋有人给了阿来一个蛋,他很开心.“我不应该吃了它”,他想,“我应该把它保存好,我应该把它放在我口袋里,那里很温暖.然后它就会成变一只小鸡.鸡蛋会变成母鸡.母鸡可以给我更多的蛋,然后就会有更多的小鸡,然后会有更多的母鸡,母鸡会给我更多的蛋.我就可以把它们卖了,我就可以成为一个富人.我就可以拥有很多袋的黄金.我就可以住在一个大房子里.房子里会有金子制成的门和窗.房子会是很大的一幢.”那时候阿来不小心把鸡蛋掉到了地上“现在我不会有钱了,”他想“我是个傻瓜.”他很伤心.
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其他类似问题
阿来的鸡蛋有个人给了阿来一个鸡蛋。他非常高兴。“我绝对不会吃了它。”阿来想。“我会把它一直留在我的口袋里。它在那儿会很温暖。不久就会孵出小鸡。这样鸡蛋就会变成一只母鸡，然后母鸡又会生出更多的鸡蛋。鸡蛋又变成更多的母鸡。更多的母鸡又会生出更多的鸡蛋。我要卖掉它们。我要变成一个有钱人。我要拥有许多带金子。我要住在一个大房子里。而且房子会有黄金做的门 和窗户。”然...
楼上两个意思都对,从信达雅的角度看,4eversnow 略微好些.
扫描下载二维码There is an egg in the bag.(就划线部分提问)
ixphhwu955
where is an egg?
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扫描下载二维码How Salty Does the Sea Have to Be for an Egg to Float?
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Difficulty
Time Required
Very Short (≤ 1 day)
Prerequisites
Material Availability
Readily available
Very Low (under $20)
Always wash your hands after handling uncooked eggs because they may carry Salmonella.
Some objects float on top of the ocean, and other objects sink to the bottom. Why? Try this eggsperiment to find out!
Determine what salt concentration will float an egg.
Andrew Olson, PhD, Science Buddies
Sandra Slutz, PhD, Science Buddies
This science fair project idea came from the following source:
ONR. (n.d.). Resources: Experiments&Saltwater vs. Freshwater, which is Denser? Retrieved May 4, 2006, from
Cite This Page
Science Buddies Staff.
"How Salty Does the Sea Have to Be for an Egg to Float?"
Science Buddies.
Science Buddies, 30 June 2014.
Web. 28 Mar. 2016
&http://www.sciencebuddies.org/science-fair-projects/project_ideas/OceanSci_p003.shtml&
Science Buddies Staff.
(2014, June 30).
How Salty Does the Sea Have to Be for an Egg to Float?.
Retrieved March 28, 2016
from http://www.sciencebuddies.org/science-fair-projects/project_ideas/OceanSci_p003.shtml
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Introduction
Did you know that if you put an egg in a cup of tap water, it will sink to the bottom? But, if you add enough salt, the egg will float back up to the surface! Why? Because the density of the egg is higher than the density of tap water, so it sinks. Density (&), as shown in Equation 1, is the mass (m) of a material per unit volume (v). For example, the density of freshwater under standard conditions is
approximately 1 gram (g) per cubic centimeter (cm3). In other words, if you filled a
1-cm&x&1-cm&x&1-cm
box with freshwater, the water inside the box would have a mass of 1 g. Adding salt to the water
increases the density of the water, because the salt increases the mass without changing the
volume very much.
With enough added salt, the saltwater solution density is higher than the egg's,
and the egg will then float, as shown in Figure 1.
The ability of something, like the egg, to float in water or some
other liquid is known as buoyancy.
Equation 1:
[Please enable JavaScript to view equation]
& = Density in whatever units are used for mass and volume.
m = Mass in grams (g), kilograms (kg), or any other unit of weight.
v = Volume in centimeters cubed (cm3), meters cubed (m3), or any other unit of volume.
Figure 1. When an egg is placed in saltwater, if the water is salty enough then the egg will float because the egg's density is less than the density of the saltwater.
This picture shows an egg floating in very salty saltwater from two different points of view.
But just how much salt is needed to make an egg float? In this science fair project, you will figure that out by using the technique of making serial dilutions. A serial dilution is a method for accurately diluting a solution in regular steps. You add a known amount of your starting, or stock, solution to a known amount of water and mix them. The new concentration will be determined by the ratio of the volume of stock solution to the total volume, as shown in Equation 2.
Equation 2:
[Please enable JavaScript to view equation]
If the volume of stock solution and the volume of water are equal, you will be diluting the
solution by half. This is called a two-fold dilution. If you want bigger steps, you
should use r if you want smaller steps, you should use relatively less water.
By repeating the process, you can make a whole series of dilutions, which is how the method got its
name. In this ocean science project, you will start out using two-fold dilutions to find out how much
salt will cause an egg to float.
Terms and Concepts
Serial dilution
Concentration
Relative concentration
Absolute concentration
Why would an egg float in water with a lot of salt in it, but not in plain tap water?
What happens to salt (sodium chloride or NaCl)
molecules when dissolved in water?
Why does adding salt to water increase its density?
Bibliography
Ophardt, C. E. (2003). Density - a Physical Property. Virtual Chembook, Elmhurst College. Retrieved June 19, 2009, from
Kenyon College. (n.d.). Serial Dilutions. Retrieved June 19, 2009, from
Swenson, H. (n.d.). Why Is the Ocean Salty? U.S. Geological Survey Publication. Retrieved May 4, 2006, from
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Materials and Equipment
Permanent marker
Table salt (1 cup)
Measuring cup, liquid
Large container, such as a large bowl or cooking pot.
Must be able to hold at least five cups.
Spoon for stirring
Bag of clear 16-oz. plastic cups
Soup spoon for egg transfer
Lab notebook
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Experimental Procedure
Note: For convenience of doing this science project using household measuring tools, volumes are given in terms of United States measuring spoons and cups.
However, science is done in metric units and students may need to convert when writing up their procedure.
To convert units, you can use the following website:
Science Made Simple, Inc. (n.d.). Metric conversions & US customary unit conversion calculator. Retrieved April 15, 2013, from
Take five eggs out of the refrigerator, use a permanent marker to label them 1-5, and allow them to warm to room temperature.
Make a stock solution of 1 cup of salt dissolved in 5 cups of water, as follows:
Pour 3 cups of water into your large container.
Add 1 cup of salt.
Stir to dissolve some of the salt.
It will not all dissolve yet.
Add 2 more cups of water.
Stir to dissolve the rest of the salt.
The salt should be completely dissolved before you go on to the next step.
This may take several (5 to 10) minutes of stirring, so you may need to be patient.
Make a two-fold serial dilution of the stock solution, as follows:
Label five of the plastic cups 1-5. Cup 1 will be for the stock solution, cups 2-4 will be for the dilutions, and cup 5 will be plain tap water.
Add 3/4 cup of your stock salt solution to cup 1.
Add 3/4 cup plain tap water to cups 2-5.
Measure out 3/4 cup stock solution, and add it to cup 2. Mix.
Measure out 3/4 cup of the solution from cup 2 and add it to cup 3. Mix.
Measure out 3/4 cup of the solution from cup 3 and add it to cup 4. Mix.
What are the relative salt concentrations of cups 1-4?
Example: Cup 2 is made up of half stock solution and half tap water, which is a 50 percent relative salt concentration.
What are the absolute salt concentrations of cups 1-4? (If you want to convert to metric units, 1 cup of salt is about 292 grams [g], and 1 cup of water is 237 milliliters [mL].) Write these concentrations down in your lab notebook.
Now, starting with cup 5 and working your way up, test an egg in each solution to see if it will float. Use a soup spoon to lift the egg in and out of the cups.
In which cup did the egg first float? (Save this solution for step 7.) If the egg floated in more than one cup, did you notice any difference in how it floated?
Be sure to record your results and observations in your lab notebook, including the egg's number.
Repeat steps 5-6 with four other eggs.
Now you know, within a factor of 2, how much salt it takes to float an egg. How can you narrow down the range further to get a more precise estimate? By doing another serial dilution, of course.
This time you will start your dilution with the salt concentration in which the egg first floated, the one you selected in step 6.
Figure out a new serial dilution with smaller steps. For example, you could try diluting the solution by 25 percent with each step. That means with each step, the new concentration should be 75 percent of the original concentration.
What amounts of stock solution and water do you need to use?
Remember that you will need enough solution to more than cover the egg, which will probably be around 3/4 cup, and you probably cannot fit more than 2 cups of solution in each 16-oz. cup.
Hint: You may only be able to test the first few cups in a dilution series at a time unless you use larger cups.
Tip: If you need additional help for making serial dilutions, check out the serial dilutions resource in the Bibliography in the
Write up your new dilution procedure in your lab notebook, including the calculated relative and absolute salt concentrations for each cup.
Make the new dilution series. Remember to start with salt concentration where the egg first floated. (If you do not have enough solution from the original serial dilution, make some more by starting from the stock solution.)
As before, test an egg in each cup, starting with the lowest salt concentration. In which cup did the egg float first?
Be sure to record your results and observations in your lab notebook, including the egg's number.
Repeat this step with the four other eggs.
If you want, make another dilution series, with even smaller steps, to improve the precision of your estimate.
Be sure to record your results and observations in your lab notebook, including the egg's number.
Repeat this step with the four other eggs.
When you are done handling the eggs, wash your hands with soap and warm water.
It is important to wash your hands after handling uncooked eggs because they may carry Salmonella.
Determine the densities for all five eggs and record this in your lab notebook.
Hint: If the density of the saltwater is less than the egg's density, the egg will sink, and if the density of the saltwater is greater than the egg's density, the egg will float.
So the density of the egg would be between these two absolute salt densities.
Plot the densities for all five eggs on a chart, putting the egg's number on the x-axis and its density on the y-axis. What is the density of the eggs? How much variation in density is there from egg to egg?
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Variations
Does a hard-boiled egg float at the same salt concentration as an uncooked one? Hint: You will need to measure the same egg before and after hard boiling and be very precise about your serial dilutions.
Find out how much salt there is in sea water. From the results of your experiment, predict whether an egg would float or sink in sea water. (If you live close enough to the ocean, you can get collect some sea water and test your prediction!)
Figure out another method of determining the density of an egg. Compare the density measurements for the same eggs using your method and this salt water float test.
For another way of looking at salt water density, see the Science Buddies project
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Recent Feedback Submissions
redneckgal said:
What was the most important thing you learned?
that different amounts of salt in water makes a egg float
What problems did you encounter?
It didn't work very well the eggs didn't float at all
Can you suggest any improvements or ideas?
Make it so the eggs do float instead of just sit in the water
Overall, how would you rate the quality of this project?
What is your enthusiasm for science after doing your project?
Compared to a typical science class, please tell us how much you learned doing this project.
Do you agree?
Childofthe1trueKing said:
What was the most important thing you learned?
That an object actually can float in salt water.
What problems did you encounter?
I had decided to use plastic cups, and if I was going t o go all the way up to 7 cups... But the cups weren't big enough.
Can you suggest any improvements or ideas?
Maybe give them a list of objects, like a penny, marble, and egg, and see how much salt was needed to make each object float, and how long it stood afloat.
Overall, how would you rate the quality of this project?
What is your enthusiasm for science after doing your project?
Compared to a typical science class, please tell us how much you learned doing this project.
Do you agree?
JulieAbell said:
What was the most important thing you learned?
A science teacher needs to do this experiment with the student and the categories of easy, intermediate, etc. are not necessarily for homeschool families.
What problems did you encounter?
I needed to contact a scientist that is a personal friend to help me understand what was being asked and how to calculate the answers.
Not even the scientist on the help forum was not helpful enough.
Can you suggest any improvements or ideas?
Recategorize this project or have better instructions.
Your &hints& are not helpful at all.
Overall, how would you rate the quality of this project?
What is your enthusiasm for science after doing your project?
Compared to a typical science class, please tell us how much you learned doing this project.
About the same
Do you agree?
BALLUP said:
What was the most important thing you learned?
the most important thing i learned was the abstract.
What problems did you encounter?
Can you suggest any improvements or ideas?
Overall, how would you rate the quality of this project?
What is your enthusiasm for science after doing your project?
Compared to a typical science class, please tell us how much you learned doing this project.
About the same
Do you agree?
Nini13 said:
What was the most important thing you learned?
How stupid plain water is cuz it dont make nothing float?
What problems did you encounter?
that eggs cant float in plain water
Can you suggest any improvements or ideas?
.i suggest that you guys make plain water float an egg duhhhhhhhhh.
Overall, how would you rate the quality of this project?
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Compared to a typical science class, please tell us how much you learned doing this project.
About the same
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Timmaster said:
What was the most important thing you learned?
What problems did you encounter?
Can you suggest any improvements or ideas?
Overall, how would you rate the quality of this project?
What is your enthusiasm for science after doing your project?
Compared to a typical science class, please tell us how much you learned doing this project.
Do you agree?
haleigh102702 said:
What was the most important thing you learned?
That it depends on what materials you use on what your outcome will be.
What problems did you encounter?
Can you suggest any improvements or ideas?
none it was perfect
Overall, how would you rate the quality of this project?
What is your enthusiasm for science after doing your project?
Compared to a typical science class, please tell us how much you learned doing this project.
Do you agree?
basketball_beast said:
What was the most important thing you learned?
How salty does water have to be for an egg to float
What problems did you encounter?
the measurements yall confusing me
Can you suggest any improvements or ideas?
Ya dont let a pre schooler write the measurements down
Overall, how would you rate the quality of this project?
What is your enthusiasm for science after doing your project?
Compared to a typical science class, please tell us how much you learned doing this project.
Do you agree?
IIOptic720 said:
What was the most important thing you learned?
densicy helps eggs float
What problems did you encounter?
haveing less salt
Can you suggest any improvements or ideas?
Overall, how would you rate the quality of this project?
What is your enthusiasm for science after doing your project?
Compared to a typical science class, please tell us how much you learned doing this project.
Do you agree?
diyaamin01 said:
What was the most important thing you learned?
that water is dencer than the egg
What problems did you encounter?
the salt wouldnt mix that well
Can you suggest any improvements or ideas?
Overall, how would you rate the quality of this project?
What is your enthusiasm for science after doing your project?
Compared to a typical science class, please tell us how much you learned doing this project.
Do you agree?
iloveclarinet said:
What was the most important thing you learned?
the rules of buoyancy and how it affects boats. also an estimate (in a smaller scale) of the amount of salt in the ocean. it also brought up lessons about buoyancy and boats in my science class.
What problems did you encounter?
the amounts of salt. the specifics amounts caused me difficulty
Can you suggest any improvements or ideas?
being more specific when it comes to measurements
Overall, how would you rate the quality of this project?
What is your enthusiasm for science after doing your project?
Compared to a typical science class, please tell us how much you learned doing this project.
Do you agree?
naynay24 said:
What was the most important thing you learned?
What problems did you encounter?
Can you suggest any improvements or ideas?
Overall, how would you rate the quality of this project?
What is your enthusiasm for science after doing your project?
Compared to a typical science class, please tell us how much you learned doing this project.
Do you agree?
gisellehermita said:
What was the most important thing you learned?
That salt has a lot of density and that is what makes the egg to be able to float inside the water. The cup that ended up with the most salt,which was cup #1, ended up being the one in which the egg floated.
What problems did you encounter?
Can you suggest any improvements or ideas?
Overall, how would you rate the quality of this project?
What is your enthusiasm for science after doing your project?
Compared to a typical science class, please tell us how much you learned doing this project.
Do you agree?
boyufd said:
What was the most important thing you learned?
why does the egg float
What problems did you encounter?
Can you suggest any improvements or ideas?
Overall, how would you rate the quality of this project?
What is your enthusiasm for science after doing your project?
Compared to a typical science class, please tell us how much you learned doing this project.
Do you agree?
Nerdygirl2002 said:
What was the most important thing you learned?
One of the most important thing i learned was the density of an egg. It was very important in my project too.
What problems did you encounter?
I had lots of promblems will doing my project but one of the main ones was how to make the stock soultion. I strugled with that the first 2 times i did the project.
Can you suggest any improvements or ideas?
I think to make the project better you sould also test a wider varitey of liqiuds that would float the egg.
Overall, how would you rate the quality of this project?
What is your enthusiasm for science after doing your project?
Compared to a typical science class, please tell us how much you learned doing this project.
Do you agree?
kamyapink said:
What was the most important thing you learned?
salt water makes things float
What problems did you encounter?
Can you suggest any improvements or ideas?
no no no no
Overall, how would you rate the quality of this project?
What is your enthusiasm for science after doing your project?
Compared to a typical science class, please tell us how much you learned doing this project.
Do you agree?
ginamarie123 said:
What was the most important thing you learned?
That salinity in water makes things float. If there isn't salinity content then nothing floats, everything sinks to the bottom.
What problems did you encounter?
Can you suggest any improvements or ideas?
Try using colored water or dyed eggs.
Overall, how would you rate the quality of this project?
What is your enthusiasm for science after doing your project?
Compared to a typical science class, please tell us how much you learned doing this project.
About the same
Do you agree?
halreve said:
What was the most important thing you learned?
i was so confused I learned nothing
What problems did you encounter?
the hole thing was a problum
Can you suggest any improvements or ideas?
not as complacated
Overall, how would you rate the quality of this project?
What is your enthusiasm for science after doing your project?
Compared to a typical science class, please tell us how much you learned doing this project.
Do you agree?
swimgirloi said:
What was the most important thing you learned?
You need a lot of salt for an egg to float.
What problems did you encounter?
I was putting in to much salt and it was collecting at the bottom, it wasn't dissolving.
Can you suggest any improvements or ideas?
Overall, how would you rate the quality of this project?
What is your enthusiasm for science after doing your project?
Compared to a typical science class, please tell us how much you learned doing this project.
Do you agree?
brezzy said:
What was the most important thing you learned?
It takes quite a bit of salt, and eggs don't float naturally.
What problems did you encounter?
I forgot to conduct an experiment that could be used as a constant.
Can you suggest any improvements or ideas?
Overall, how would you rate the quality of this project?
What is your enthusiasm for science after doing your project?
Compared to a typical science class, please tell us how much you learned doing this project.
Do you agree?
Ask an Expert
The Ask an Expert Forum is intended to be a place where students can go to find answers to science questions that they have been unable to find using other resources. If you have specific questions about your science fair project or science fair, our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.
Related Links
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