Question

HEAT

INTRODUCTION
Heat is a measure of the energy in a system. The transfer of energy is always from the system with more energy to the system with less energy. This lab has two distinct parts. In the first part, you will examine what happens to a gas when the temperature is changed. In the second part, you will use the idea of energy transfer to move water. You will need to be familiar with the ideas of phases (solid, liquid and gas), what specific heat is, and how to calculate joules. Please see pages 93-94, 99-101, and 106-110 in your textbook.
MATERIALS
1 small mouth (or small neck) bottle… a soda bottle should work
1 coin (dime or penny – must cover completely mouth of bottle)
1 large container to submerge at least ½ the bottle (sink, tub, bowl, etc.)
Enough cold water to submerge ½ the bottle
Measuring cups
Food coloring – in kit
4 cups water
1 large bowl to hold water – a clear glass one works best
1 small glass that will extend above water level when in bowl
Saran wrap/cling film – enough to cover bowl
1 small object (example: pebble, coin, marble)
Sunny days (3-4)
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PART#1: Magic Coin?
Procedure:
Fill selected container with some cold water.
Place the bottle and coin in the bowl of water to chill them. The bottle must be submerged upside down. Submerge at least the neck of the bottle but if you have no “coin activity” on step four, repeat this step with either a greater amount of submersion or submerge the bottle for a greater amount of time.
Place the coin on the top of the bottle. There should be an airtight seal when you place the coin on the top of the bottle.
Wrap your hands around the bottle and wait for several seconds to a minute.
When you believe that the bottle is warmer than room temperature, allow the bottle to cool with the coin in place. Answer the following questions based on your observations.
Questions:
Approximately how long did you submerge the bottle in step #2?
What happened during step #4?
What happened during step #5?
Explain what is happening to the molecules to create the “coin activity”.
PART#2: Distillation
Procedure:
Add the water to the bowl.
Stir in the food coloring until it is distributed equally.
Place the empty glass (small) in the middle of the large bowl so that none of the
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colored water can get into the glass. The glass must be short enough that it does not extend beyond the rim of the glass bowl.
Note: If the glass bowl is not working because the small empty glass is not stable, a stock pot/dutch oven (with a flat bottom) will work but it will need to be left alone for a little more time.
Cover the large bowl completely with the saran wrap so that no air can pass through.
Add the small object on the saran wrap so that the saran wrap dips in over the small empty glass but does not cause the saran wrap to slip off the lip of the bowl. Use a smaller pebble or coin if the first one is too heavy.
Leave the bowl in the sunlight for a few days and watch to see what happens.
Remove the small glass and measure the amount of water in it with the measuring cups (estimating to the nearest 1/8 cup). Contact me immediately if the amount of water in the small glass is less than 1/8 cup.
Questions:
How is the water in the large bowl different from the water in the small glass?
Describe step by step what happened to the water that is now in the small glass in terms of heating/cooling, phase changes, etc. (Hint: there is more than one step required)
How many cups of water (to the nearest 1/8 cup) are in the small glass?
How many grams of water did you collect?
The relationship between cups and grams is: 1 cup = 236 grams
How many calories are needed to heat the water?
Assume the following information:
The original temperature of the water in the large bowl was 25 °C.
The temperature of a molecule that changes from liquid to gas is 100 °C.
The specific heat of water is 1.00 cal/g·°C
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You will need the equation for specific heat (equation 4.4)
How many calories are needed to evaporate the water?
The latent heat of vaporization of water is 540.0 cal/g
You will need equation 4.6 in the textbook.
How many calories (total) are needed to “move” the water from the large bowl to the small glass?
Notes: Ignore the amount of water that was not “moved” The water molecules must warm AND change state

Answer 1

The specific heat is used to understand and calculate the energy required for temperature changes and phase transitions in substances. In lab demonstrations, the heat transfer in reactions can be quantified using calorimetry, emphasizing the importance of heat capacity and the specifics of the calorimeter design.

The specific heat of a substance is an intensive property that represents the energy required to change the temperature of 1 gram of the substance by 1 degree Celsius. In the context of the lab described, understanding the specific heat is crucial to calculating the energy transfer during the heating or cooling of water, as well as phase changes that occur during the distillation process. The demonstrations in the lab illustrate the concept of heat transfer and the effects of temperature change on the behavior of molecules.

For example, when a 500-mL and a 2-L bottle of water are placed in a refrigerator, the bottle with more water (2-L) loses more heat, simply because there is a greater amount of water to lose heat. In cases of calorimetry, when a substance or a reaction occurs in water, the heat transfer is measured to determine the energy change associated with the reaction. The calorimeter, as mentioned, is a tool used to measure this heat transfer. It is important to consider the heat capacity of the calorimeter and any material involved when calculating the energy transfer within the system.