Science Project Planning

[Jonathan]

Hello.

In the last trial, the fresh water froze at -5 degrees in temperature. I did use this thermometer before and could be an error with thermometer? I have to go back to school again for another play.
I will try doing the experiment tomorrow after school.

I will use 7 oz. of water and 1/8 oz, 1/4 oz and 3/4 oz of salt. I used the scale before to measure the salt but the amounts were 1/2 and one ounce. My scale is not digital. I hope my dad can help me figure out how to measure 1/8 oz. on the scale.

If you think of anything else, please let me know.

Jonathan

[Louise]

Hello.

In the last trial, the fresh water froze at -5 degrees in temperature. I did use this thermometer before and could be an error with thermometer? I have to go back to school again for another play.
I will try doing the experiment tomorrow after school.

I will use 7 oz. of water and 1/8 oz, 1/4 oz and 3/4 oz of salt. I used the scale before to measure the salt but the amounts were 1/2 and one ounce. My scale is not digital. I hope my dad can help me figure out how to measure 1/8 oz. on the scale.

If you think of anything else, please let me know.

Jonathan

I would check for an error with a thermometer. It seems very odd that it would be so low.

I understand what your problem is with the scale now. Thank you for clarifying. You could weigh out 1/2 oz, and dissolve it in 28 oz, and then only pour out 7 oz in to the container to freeze.

Have fun at the play!

Louise

[Jonathan]

Hello.

I'm working on my experiment. I'm testing with 7 ounces. For the salt samples, I took 7 ounces from the mixture of (1/2 oz, 1 oz. and 1 1/2 oz. of + 28 ounces of water) like you told me.

This is what I'm observing:

After 30 minutes: Fresh Water Froze on Top - 0 Degrees Celsius
After 40 minutes: 1/2 oz. salt water - some ice needles - 0 Degrees Celsius
After 50 minutes: 1 1/2 oz. salt water - some ice needles - 0 Degrees Celsius

Everything is happening quicker since I have so much less water. I will continue to look until the fresh water completely freezes. I want to be able to collect more data also.

Please let me know if you think of anything else that I should do. I will give you more information later tonight.

Thank you.
JONATHAN

[Jonathan]

Hello.

These are my results:

After 130 minutes, Fresh water froze - 0 degrees temperature
After 190 minutes, 1/2 oz. salt water slush semi-froze at -5 degrees temperature
After 190 minutes, 1 oz. salt water slush semi-froze at -7 degrees temperature
After 190 minutes, 1 1/2 oz salt water firm slush at -10 degrees temperature

I'm going to bed now. I think it will freeze by morning. Please let me know what you think. Then I will do another trial.

Thank you.
JONATHAN

[ChrisG]

Well done, Jonathan. You're a devoted experimentalist.

[Jonathan]

Thank you.

This morning I looked at the samples again. I used a clear cup so that I can see the inside better.
The salt samples - are cloudy looking and bumpy looking. My mom describes the salt samples as frozen slush but with a liquid film on top. The one with the most salt has the most liquid on top.

After 18 hours, the salt samples froze also but with the liquid film on top at temperatures of -15, -18 and -20 degrees celsius. Should I include this data in my charts?

What type of chart should I use to plot my data - bar graph or line graph?

I will do my trials this weekend.

Thank you...Jonathan

[Louise]

Thank you.

This morning I looked at the samples again. I used a clear cup so that I can see the inside better.
The salt samples - are cloudy looking and bumpy looking. My mom describes the salt samples as frozen slush but with a liquid film on top. The one with the most salt has the most liquid on top.

After 18 hours, the salt samples froze also but with the liquid film on top at temperatures of -15, -18 and -20 degrees celsius. Should I include this data in my charts?

What type of chart should I use to plot my data - bar graph or line graph?

I will do my trials this weekend.

Thank you...Jonathan

This sounds great!

You can use a line graph for each sample to plot all of your time data, so people can see how the temperature dropped with time. (Only use the trials with the same amount of water, because the time gets faster with the smaller containers)

I think a bar graph would be best for the final temperatures. You can use the data for all trials with the same amount of salt, so you first trial (in 28 oz) and this last one, and the trial you are doing on the weekend.

Louise

[ChrisG]

In addition to Louise's excellent suggestions, you could also make a scatter plot (a graph with points but not lines) of salt concentration on the x-axis versus the freezing temperature on the y-axis. With this type of graph, you could plot all your data from all your trials, using a different symbol for each trial. Here is an explanation of a scatterplot, in case that term is unfamiliar to you:
http://www.mste.uiuc.edu/courses/ci330m ... rinfo.html
Scatterplots are also mentioned here:
http://www.sciencebuddies.com/science-f ... ysis.shtml

[tdaly]

Another way that you may able to check if your freezer really is at 0 C would be to put a thermometer in the freezer and let it stay there for a while and then see what reading the thermometer gives you. This wouldn't give you information on the accuracy of the thermometer necessarily, but it would help you know if the reading you got in the cup with salt was reasonable compared to the temperature of your freezer given by the thermometer.

[Jonathan]

Hello.

I had a busy week in school before vacation. My teacher gave a test almost everyday and I had to study.

I'm happy to do another trial today. Yes - I do have two thermometer's in my freezer. They both read -19 degrees. So the readings I'm getting do seem reasonable. i asked about this before. My dad is a bit surprised that my home freezer is able to go to -19 degrees.

THANK YOU.
JONATHAN

[tdaly]

Jonathan,

Just because your thermometers read -19 degrees (is this Fahrenheit or Celsius?) doesn't nessecarily mean your freezer is actually at -19 degrees, because, as the other experts have discussed, your thermometers might not be well-calibrated. What it does mean is that now you have a rough idea of the sort of temperature readings your thermometers are giving so that you have an idea of the different temperatures relative to one another. Does this make sense?
If not, please let me know and I will try to explain better.

Good luck with your experiment today and have fun!

[Jonathan]

Hello.

I understand. The -19 degree temperature is celsius.

I'm still working on my experiment. I'm also starting to research water websites with my mom.

I will let you know how I did later on.

Thank you.
JONATHAN

[ChrisG]

With two thermometers reading -19C, and both thermometers having been calibrated at -35C, it seems safe to report the measured value. This temperature is in the recommended range for long-term storage of frozen food, -15 to -20C. I can understand why your dad was surprised - I was also surprised when I first read the recommended temperature range - but when you think about the results of this experiment, it makes perfect sense.

Of course, different parts of the freezer will have different temperatures, and the temperature will change when the door opens and closes.

Keep up the good work!

[Louise]

Hello.

I understand. The -19 degree temperature is celsius.

I'm still working on my experiment. I'm also starting to research water websites with my mom.

I will let you know how I did later on.

Thank you.
JONATHAN

Good luck completing your project. I agree with Chris; I think you done a lot to make sure your readings are accurate and you can be confident in them (within the errors you found when you calibrated all thermometers). I also wanted to say that I liked Chris's idea of a scatter plot. I suggested a 'bar plot' which would be the average value for all trials. The scatter plot whould show all data and how each trial was different. Both would tell someone looking at your board something very important.

Louise

[Jonathan]

Hello.

My brother is helping me do the charts. The question i have is why does salt water freeze at a low temperature thats negative.

Thank you
Jonathan