The final is mostly finished and things to remember are on the facebook page pictures of the board. You should know the relationships I just outlined in the previous post between temperature, pressure and volume. You should also look over your specific heat homework and know how to do those problems. You should be able to define pressure, PSI, density and especially know that temperature and heat are different. Temperature is a tendency to transfer heat. Heat is energy. Know your temperature scales. Know what specific heat capacity means.
We'll have a few minutes to answer questions at the beginning of class if you are unclear about some of these things.
Good luck. If you have time tonight or tomorrow I'd greatly appreciate for you to write in questions, comments or concerns about the usefulness of this space and the Facebook page and if it could be used better.
Wednesday, May 30, 2012
Gas Laws Help
The three gas laws are Charles Law, Boyle's Law and Gay-Lussac's Law. This is the clearest statement of it I've found and yes, if you look, it's from Wikipedia (don't listen to your teachers when they tell you Wikipedia is terrible. Mostly it's amazing) Charles's law states that volume and temperature are directly proportional to each other as long as pressure is held constant. Boyle's law asserts that pressure and volume are inversely proportional to each other at fixed temperature. Finally, Gay-Lussac's law introduces a direct proportionality between temperature and pressure as long as it is at a constant volume. The inter-dependence of these variables is shown in the combined gas law, which clearly states that:
Pressure and temperature, at a fixed volume, are proportional, so that if the temperature goes up, as in the experiment Tala and I were doing at the front of the class (#3), then the pressure goes up. If you graph them it should be a straight line.
| “ | The ratio between the pressure-volume product and the temperature of a system remains constant. | ” |
Volume and Temperature, as we saw when we dunked the syringe in water, are also proportional. As temperature goes up, you volume also wants to increase. As the one goes up, the other goes up proportionally i.e. in a straight line.
Volume and Pressure: These two are inversely proportional As we increased pressure (added books) we saw the volume decrease. It decreased a lot when you put the first book on it, and decreased increasingly less per book as the number of books increased. So as pressure goes up, volume goes closer to zero.
If there are more questions, post below. I'll be checking frequently for the next couple hours. Remember, if you want me to look at it, I need to have your write up in tomorrow!
Sunday, May 27, 2012
No Quiz on Tuesday, Final on Thursday
There will not be a quiz on Tuesday May 29, but you will have your final exam on Thursday May 31 so that I can be there to answer question about the test while you are taking it.
Thursday, May 24, 2012
For your lab journal, Mass and Density
Please add to your lab journals a description of mass, and how we found that 1 gram of water is equal to 1 ml of water. Also show what density is (mass/volume = density) and how things with more density float on things with less density. Use an example, either the density column or ice sinking in alcohol and floating on water and then what we measured their densities at water = 1g/ml and alcohol = .82 g/ml
This can be a very short entry.
Thanks guys.
This can be a very short entry.
Thanks guys.
Tuesday, May 22, 2012
Specific Heat Capacity Table
The middle column is in different units then we've been using, so just notice the ones on the right.
Monday, May 21, 2012
Assignment 6 due May 22 (Tomorrow)
Hey everybody, here's the hw for tonight and remember to keep track of your units: Calories for Q, Cal/mlC for c, ml for volume and Degrees Celsius for T. I Changed the numbers slightly so that they should work better, but don't rely on them working perfectly.
Expect c to change with the modified numbers. It should be close to, but more than 1.00
Calculating the specific heat of oil: Name__________
Remember the equation Q=cV∆T
These are slightly modified numbers from Gavin’s sheet:
1.) Trial 1: The temperature of 75ml of water changes from 80 0F to 149 0F over three minutes of being heated by a constant flame. Calculate the number of calories added by multiplying the change in temperature by the volume of water.
Trial 2: For the 150ml of water, the temperature began at 68 0F and ended at 102 0F. How many calories were added?
Trial 3: for 225ml of water the temperature started at 750F of water and ended at 100 0F. How many calories were added?
Find the average calories added by adding together the calories found in all 3 trials and then dividing by 3.
2.) Oil trials: Figure out the specific heat of oil by setting up the equation Q=cV∆T where V is your 75ml, Q is your average Q from trials Q=cV∆T and, for this trial, your initial temperature is 84 0F and your final temperature is 148 0F
Find c again with trial two where V = 150, your initial temperature is 86 0F and your final temperature is 118 0F.
What is your average c?’
Expect c to change with the modified numbers. It should be close to, but more than 1.00
Calculating the specific heat of oil: Name__________
Remember the equation Q=cV∆T
These are slightly modified numbers from Gavin’s sheet:
1.) Trial 1: The temperature of 75ml of water changes from 80 0F to 149 0F over three minutes of being heated by a constant flame. Calculate the number of calories added by multiplying the change in temperature by the volume of water.
Trial 2: For the 150ml of water, the temperature began at 68 0F and ended at 102 0F. How many calories were added?
Trial 3: for 225ml of water the temperature started at 750F of water and ended at 100 0F. How many calories were added?
Find the average calories added by adding together the calories found in all 3 trials and then dividing by 3.
2.) Oil trials: Figure out the specific heat of oil by setting up the equation Q=cV∆T where V is your 75ml, Q is your average Q from trials Q=cV∆T and, for this trial, your initial temperature is 84 0F and your final temperature is 148 0F
Find c again with trial two where V = 150, your initial temperature is 86 0F and your final temperature is 118 0F.
What is your average c?’
Friday, May 18, 2012
Assignment 5 Specific Heat
Please answer the questions at the end of the handout and graph your results as detailed by Monday!
Lab 4: Specific Heat
Introduction:
We know that different materials heat more or less quickly depending upon their heat conductivities. But what will happen if you take exactly equal amounts of different substances and apply the exact same amount of heat to each? What if you have twice as much material? In this lab we will find out.
Materials:
Hot Plate Beakers Graduated cylinders Oil (vegetable) Water
Timer (accurate to the second) Thermometer
Procedure:
Get into groups of four. Using the graduated cylinder, measure into your beakers the water and oil as exactly as you can: you will be heating 75ml of water, 150ml of water, 225ml of water, 75ml of oil, and 150ml of oil. You may need to re-use beakers if we don’t have enough. In this case, do your three water-trials first, then do the two oil-trials (see below). DO NOT put oil in a beaker and then use it for water without thoroughly cleaning it out first.
For each trial, you will first place the CLEANED thermometer in the liquid and wait for its temperature to stabilize. Turn your burner to its highest temperature. NEVER MOVE THE BURNER, OR TURN ITS KNOB, even between trials – this gives consistent results by continuously providing the same amount of heat. Wait 4 minutes for the hot plate to heat up to maximum temperature.
Get ready to use the second hand of your watch or the clock at the back of the room, and carefully place a beaker on top of the hot plate. The temperature of the liquid at time = 0 seconds is the initial starting temperature.
You will be taking temperature measurements every 10 seconds for 180 seconds (three minutes), and no longer – record these results below. Be very careful not to break the thermometer. Once you are finished, carefully remove the beaker with the tongs. If the substance in the beaker is water, pour it into the sink. If it is oil, set it aside in a safe place and let it cool (or pour it into another beaker) – use the other beakers to continue the experiment. Once you are done and all your oil is cooled down, pour it back into the original bottles using a funnel. DO NOT POUR THE OIL DOWN THE SINK.
Repeat the above heating and measuring procedure for each trial – you will have five total trials. Everyone in the lab group should record the temperatures in the chart below in degrees Celsius.
Make note of any other observations here (sights, sounds, smells):
Analysis:
Once you have all the data above, you will need to put the data into a single graph, in order to check for patterns.
On a piece of graph paper, create a graph that contains all of the above data. Color code each row above, and plot your points in the same color. Put time on the x-axis and temperature on the y-axis. Your graph needs to fill the entire sheet (and therefore should be made in landscape format rather than portrait). You must have a title on the graph, and you must put in a legend or key showing which colored points belong to which ‘data set’ (or row: in this case, for example, “Water, 75ml”).
Now you will look for a pattern or trend in a particular part of the data, for which you can draw in a “trendline” or a “best-fit curve”. A best-fit curve or trendline expresses in a single gesture the nature of the data and allows you to extrapolate beyond the data set you obtained observationally. This is NOT, I repeat, NOT, a connect-the dots line. A trendline is like an average of all the data points and is a smooth curve or line.
Questions to answer and hand in before class Monday:
Compare the graphs made by each row of data. What kinds of conclusions can you draw from this data?
Can you say anything in general about the nature of substances given the fact that the same amount of heat was applied to each beaker?
What makes one liquid heat up more quickly than the other? Can you form a hypothesis that is testable with a new experiment?
What were the probable sources of error in this experiment?
What could be done to improve this experiment?
Extra: What do you think would happen if you repeated the experiment but with a flame twice as hot?
Lab 4: Specific Heat
Introduction:
We know that different materials heat more or less quickly depending upon their heat conductivities. But what will happen if you take exactly equal amounts of different substances and apply the exact same amount of heat to each? What if you have twice as much material? In this lab we will find out.
Materials:
Hot Plate Beakers Graduated cylinders Oil (vegetable) Water
Timer (accurate to the second) Thermometer
Procedure:
Get into groups of four. Using the graduated cylinder, measure into your beakers the water and oil as exactly as you can: you will be heating 75ml of water, 150ml of water, 225ml of water, 75ml of oil, and 150ml of oil. You may need to re-use beakers if we don’t have enough. In this case, do your three water-trials first, then do the two oil-trials (see below). DO NOT put oil in a beaker and then use it for water without thoroughly cleaning it out first.
For each trial, you will first place the CLEANED thermometer in the liquid and wait for its temperature to stabilize. Turn your burner to its highest temperature. NEVER MOVE THE BURNER, OR TURN ITS KNOB, even between trials – this gives consistent results by continuously providing the same amount of heat. Wait 4 minutes for the hot plate to heat up to maximum temperature.
Get ready to use the second hand of your watch or the clock at the back of the room, and carefully place a beaker on top of the hot plate. The temperature of the liquid at time = 0 seconds is the initial starting temperature.
You will be taking temperature measurements every 10 seconds for 180 seconds (three minutes), and no longer – record these results below. Be very careful not to break the thermometer. Once you are finished, carefully remove the beaker with the tongs. If the substance in the beaker is water, pour it into the sink. If it is oil, set it aside in a safe place and let it cool (or pour it into another beaker) – use the other beakers to continue the experiment. Once you are done and all your oil is cooled down, pour it back into the original bottles using a funnel. DO NOT POUR THE OIL DOWN THE SINK.
Repeat the above heating and measuring procedure for each trial – you will have five total trials. Everyone in the lab group should record the temperatures in the chart below in degrees Celsius.
| (ml) | 0s | 10 | 2 | 30 | 40 | 50 | 60 | 70 | 80 | 90 | 100 | 110 | 120 | 130 | 140 | 150 | 160 | 170 | 180 |
| H20 75ml | |||||||||||||||||||
| h20 150 | |||||||||||||||||||
| h20 225m | |||||||||||||||||||
| Oil 75ml | |||||||||||||||||||
| Oil 150ml |
Make note of any other observations here (sights, sounds, smells):
Analysis:
Once you have all the data above, you will need to put the data into a single graph, in order to check for patterns.
On a piece of graph paper, create a graph that contains all of the above data. Color code each row above, and plot your points in the same color. Put time on the x-axis and temperature on the y-axis. Your graph needs to fill the entire sheet (and therefore should be made in landscape format rather than portrait). You must have a title on the graph, and you must put in a legend or key showing which colored points belong to which ‘data set’ (or row: in this case, for example, “Water, 75ml”).
Now you will look for a pattern or trend in a particular part of the data, for which you can draw in a “trendline” or a “best-fit curve”. A best-fit curve or trendline expresses in a single gesture the nature of the data and allows you to extrapolate beyond the data set you obtained observationally. This is NOT, I repeat, NOT, a connect-the dots line. A trendline is like an average of all the data points and is a smooth curve or line.
Questions to answer and hand in before class Monday:
Compare the graphs made by each row of data. What kinds of conclusions can you draw from this data?
Can you say anything in general about the nature of substances given the fact that the same amount of heat was applied to each beaker?
What makes one liquid heat up more quickly than the other? Can you form a hypothesis that is testable with a new experiment?
What were the probable sources of error in this experiment?
What could be done to improve this experiment?
Extra: What do you think would happen if you repeated the experiment but with a flame twice as hot?
Subscribe to:
Posts (Atom)
