Project 2. (60 points). Submit by 0ct 6. Recognize the role of the polarity of w
ID: 114290 • Letter: P
Question
Project 2. (60 points). Submit by 0ct 6.
Recognize the role of the polarity of water molecule by conducting simple experiments.
A) 14 pts. Experiment 1. Take picture of 1/8 tablespoon of salt, and a cup of tap water. Place 1/8 tablespoon of salt in the cup of water. Stir carefully and check if the salt lies at the bottom of cup or if it does not. Describe what you had observed, and state what property of water explains might you have observed.
.B) 16 pts. Experiment 2. Marshmallow experiment. (2pts) Measure the size of a marshmallow and (2pts) take its picture. Place the marshmallow in a microwave and switch on the microwave oven for 6 seconds. (2pts) Observe and describe the size of the mallow in the microwave. Take it out side of the microwave oven, and (2pts) measure its size, (2pts) take a picture. and (2pts) report the result.
... (4 pts) Report the diameter of the mallow before heating ___ cm, and the diameter after heating _____ cm.
C)12 pts. Before and after the microwave was switched on, the temperature around the mallow and the room were the same. By contrast, the temperature of the mallow was not.
(6pts) Explain why the marshmallow puffs up against the air in the microwave when the microwave was switched on?
Open the door of the microwave, and(2pts) describe and (4pts) explain what happened to the mallow.
D) 12pts. Based upon that experiment, write decrease or increase, no change in the correct provided dashed line, to show the relationship or correspondence to the following.
Increase in heat corresponds to:
1d) _______________ in area [A] and volume [V]
2b) _________________ in the mass[m]
2c) ______________ in density []. [= m/V]
E) 6pts. State true or false in each of the following conditions.
1 E) Wind blows from cold to hot region.
2 E) Wind blows from a region of high pressure to a region of low pressure.
3 E) Wind blows from land to the ocean at night.
Explanation / Answer
A. Salt has dissolved in water. Water can dissolve salt because the positive part of water molecules attracts the negative chloride ions and the negative part of water molecules attracts the positive sodium ions. i.e water exhibits polar nature.
B. Diameter of the marshmallow has to increase and depends up on the marshmallow you take.
C. Micro wave oven cooks food by exposing it to electromagnetic radiation in the microwave frequency range. This induces polar molecules in the food to rotate and produce thermal energy in a process known as dielectric heating. And hence the only particles affected would be the food particles, here marshmallow.
If you rip open a marshmallow and look at it with a magnifying glass, you can see that it has a lot of little holes in it. Each of these holes is filled with air. When you put the marshmallow in the microwave, you cause the air in each hole to heat up. Hotter air pushes outward with more pressure, so it pushes on the walls of the holes and the holes expand --especially because the heating also makes the marshmallow material softer and stretchier. This process is similar to blowing air into a soap bubble.
At first it expands, because it is full of air, and the air expands. But it is porous, so the air eventually escapes, and then the marshmallow just melts, and gets all gooey, because sugar has a very low melting point. Also, marshmallows have gelatine, which also melts easily. If you cook your marshmallow for too long, it turns brown or black inside.
1d) increase in area and volume
2b) no change
2c) decrease (because density is mass / volume, and mass does not change and volume increases)
1 E) True
2 E) True
3 E) True
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