Archive for the ‘class xii physics project’ Category

Science Projects {Physics}~What’s the Fastest Way to Cool a Soda?

September 1, 2008

Objective

The goal of this project is to determine the fastest method to cool a can of soda starting at room temperature.

Introduction

This project is all about heat transfer. How can you cool off a can of soda to take it from room temperature down to a nice, cold, drinkable temperature quickly, with materials that are readily available in your house?

Sure, you could put the soda in the refrigerator, but you probably know from experience that it’s going to take awhile to get really cold that way. Maybe more time than you’re willing to wait on a hot summer day. You could also try the freezer, since it’s colder, it may cool faster than the fridge. What else could you try? How about putting the soda on ice, or immersing it in an ice-water bath? Which method do you think would be most efficient at cooling a soda?

In order to get the most out of this project, you will need to do some background research on heat and heat transfer. Here is a quick summary, so that you can be familiar with the terms you will encounter. All matter is made of atoms and molecules that are constantly in motion. Even in solids, the molecules are constantly vibrating. Heat is a measure of the average molecular motion of matter. Heat can be transferred from one piece of matter to another by four different methods:

  • Conduction
  • Convection
  • Evaporation
  • Radiation

Conduction is heat transfer by direct molecular interactions, without mass movement of matter. For example, when you pour hot water into a cup, the cup soon feels warm. The water molecules colliding with the inside surface of the cup transfer energy to the cup, warming it up.

Convection is heat transfer by mass movement. You’ve probably heard the saying that “hot air rises.” This happens because it is less dense than colder air. As the hot air rises, it creates currents of air flow. These circulating currents serve to transfer heat, and are an example of convection.

Evaporation is another method of heat transfer. When molecules of a liquid vaporize, they escape from the liquid into the atmosphere. This transition requires energy, since a molecule in the vapor phase has more energy than a molecule in the liquid phase. Thus, as molecules evaporate from a liquid, they take away energy from the liquid, cooling it.

Radiation is the final way to transfer heat. For most objects you encounter every day, this would be infrared radiation: light beyond the visible spectrum. Incandescent objects—like light bulb filaments, molten metal, or the sun— radiate at visible wavelengths as well.

In both the freezer and the refrigerator, cold air is removing heat from the room-temperature soda can by convection. (There is also a small amount of heat loss via conduction, where the can is in direct contact with the shelf.) The molecules in a gas, such as air, are spread out over a much larger volume than molecules in a liquid. In other words, air (at standard temperature and pressure) is much less dense than water. If you immerse the can of soda in a cold liquid, then, you would expect that a much greater number of molecular interactions would result. Will the soda cool off faster as a result?

Terms, Concepts and Questions to Start Background Research

To do this project, you should do research that enables you to understand the following terms and concepts:

  • Kinetic theory of matter
  • Heat
  • Heat transfer
    • Conduction
    • Convection
    • Evaporation
    • Radiation

Questions

  • How does the kinetic theory of matter relate to heat transfer?
  • How does a refrigerator or freezer work to keep things cold?
  • Which do you think would be more efficient for cooling: a mass of cold air, or a mass of cold water?

Bibliography

Materials and Equipment

To do this experiment you will need the following materials and equipment:

  • 12 cans of soda at room temperature
  • Instant-read digital thermometer
  • Two styrofoam coolers
  • Ice cubes
  • Water
  • Clock or timer
  • Plastic wrap

Experimental Procedure

  1. Do your background research so that you are knowledgeable about the terms, concepts, and questions, above.
  2. Prepare an ice-only bath by adding enough ice to a styrofoam cooler to completeley cover three cans of soda.
  3. Prepare an ice-water bath by adding the same amount of ice to a second styrofoam cooler, then covering the ice with water.
  4. Use the instant read thermometer to measure the starting temperatures of:
    • the freezer compartment,
    • the refrigerator,
    • the ice-only bath,
    • the ice-water bath, and
    • each room-temperature can of soda. You’ll need to open the cans of soda to take the temperature of the liquid inside. To minimize evaporation, cover the opening with a wad of plastic wrap after taking the temperature.

    In each case, make sure that the temperature has stabilized before recording the result. For example, it may take a minute or two before the ice-water temperature reaches equilibrium when the water is first added to the ice.

  5. Place three cans of soda in each of the cooling devices to be tested, i.e.:
    • The freezer compartment
    • The refrigerator
    • The ice-only bath
    • The ice-water bath
  6. Note the starting time for each cooling device.
  7. At regular intervals (e.g., every 5 minutes), quickly remove each set of cans from their cooling device and measure the temperature of the soda. Note the time and temperature reading, then quickly put the cans back in the cooling device. Tips:
    • Minimize the amount of time that the refrigerator and freezer doors are open.
    • It is a good idea to periodically re-check the temperatures of the cooling devices.
  8. The experiment is complete when the temperature reading of the soda stabilizes.
  9. For each cooling device, calculate the average temperature of the three soda cans for each time point.
  10. Make a graph of the average temperature of the soda (y-axis) vs. elapsed time (in minutes) since the beginning of the experiment. Use a different symbol and color for each cooling device.
  11. Which cooling method worked the fastest?

Science Projects {Physics}~Build a Motorboat Powered by Surface Tension

September 1, 2008

Objective

This project has three objectives:

  1. develop a qualitative understanding of water surface tension,
  2. understand changes in water surface tension under various conditions,
  3. make measurements to estimate the net water surface tension.

Introduction

You probably have experience blowing up a balloon. For a balloon made of soft, stretchy rubber, it is easy to blow it up without becoming out of breath. The balloon offers little resistance to becoming stretched out as it is blown up. But for a balloon made of thicker or stiffer rubber, more energy is required to blow it up. The balloon offers more resistance to stretching. We can think of a balloon as a model for surface tension. How “stretchy” the balloon material is determines how much resistance (surface tension) must be overcome by the energy of your blowing in order to inflate the balloon.

Surface tension is defined as the energy required to increase the surface area by a unit amount. Liquids also experience surface tension. The molecules of the liquid experience intermolecular attractions, the details of which depend on the chemistry of the particular liquid. The molecules at the surface of the liquid experience asymmetric forces, since one side of the molecule faces the liquid, and the other side faces air. This asymmetric force is surface tension.

Water may seem ordinary, but is has some extraordinary chemical attributes. One of these attributes is hydrogen bonding. To really understand the surface tension of water, you should do some background research on the chemical structure of water and hydrogen bonding.

The effects of surface tension can be observed easily in our daily life. For example, soap bubbles, water rising inside a capillary tube, floating a needle on a still water surface, floating of water strider on water, using detergent to clean up kitchen utensils, and many others. At the smaller scales of microscopic or nanoscopic worlds, the forces of surface tension play an increasingly important role determining the behavior of molecules.

In this project, you’ll make a small boat from a clear plastic sheet (transparency), and see if you can propel it by taking advantage of the surface tension of water. All right, it’s more of a motor-raft, but maybe you can think of a good way to make a lightweight boat for this project.

Terms, Concepts and Questions to Start Background Research

To do experiments on surface tension, you should do research that enables you to understand the following terms and concepts:

  • surface tension
  • water molecules
  • hydrogen bonding of water molecules
  • detergent
  • capillary motion
  • acceleration
  • velocity

Bibliography

Materials and Equipment

  • transparency
  • scissors
  • several cotton balls, cotton swabs or small pieces of sponge
  • marker
  • ruler
  • stop watch, accurate to 0.01 s
  • postal weighing scale
  • glue or tape
  • liquid detergent
  • soap
  • toothpaste
  • water
  • thermometer (optional)
  • a few small pieces of wood to make a straight channel for your raft

Experimental Procedure

  1. Exploring the existence of surface tension
    1. Think of a shape for your raft and draw the shape onto the transparency.
      • The raft should be symmetric.
      • You will need a slot should at the end of the raft in order to insert a piece of cotton or sponge for the storage of “fuel.”
    2. Cut out the raft and insert the cotton or sponge in the slot.
    3. Prepare fresh water in a bathtub or basin.
    4. Put the raft onto the water surface and let it float.
    5. Put a drop of detergent onto the cotton or sponge at the end of the ship.
    6. Observe the motion.

    From your background research, you should know that detergents decrease the surface tension of water. How can this help to explain your results?

  2. What other substances can work as a surface-tension motor for your raft?
    1. Prepare fresh water in a bathtub or basin.
    2. Change the cotton or sponge of the raft.
    3. Put the raft onto the water surface and let it float.
    4. Put a drop of soap or toothpaste or some other substance onto the cotton or sponge at the end of the ship.
    5. Observe the motion and compare to the first raft.

  3. Exploring the effect of shape on the motion of your raft
    1. Design another shape of a ship projection and draw the shape onto the transparency.
      • You may want to try an asymmetric shape.
      • You may want to experiment with different sizes, or different basic shapes.
    2. Cut out the raft and insert the cotton or sponge at the end of the raft.
    3. Prepare fresh water in a bathtub or basin.
    4. Put the raft onto the water surface and let it float.
    5. Put a drop of detergent onto the cotton or sponge at the end of the ship.
    6. Observe the motion and compare to the other rafts.

  4. Measurement of Net Surface Tension
    1. Prepare a new raft with a shape similar to the one below:
      Example raft drawing.
      The length of the raft is quite flexible but for the first trial, it is suggested to be 3–5 cm long, and a width approximately half of this length.
    2. Weigh the raft.
    3. Prepare the a channel for your raft, marked with a predetermined distance (see drawing, below):
      Top view and end view drawings of channel for measuring acceleration and speed of raft.
      The length of the channel is suggested to be about 25 cm long with the width of the channel just slightly larger than the width of the raft. The height is about 3 cm. If you make bigger boats, you’ll need to adjust the dimensions accordingly.
    4. Prepare fresh water in a bathtub or basin.
    5. Put the raft at one end of the channel and put a drop of detergent onto the cotton or sponge at the end of the ship.
    6. Measure the time required for the raft to travel inside the channel between the predetermined marks.
    7. Calculate the acceleration and the kinetic energy imparted to the boat.
    8. Increase the mass of the raft by adding more pieces of transparency (record the new weight).
    9. Repeat the measurement and calculations for several weights of the ship.
    10. Compare the measured values.

Variations

  1. How would changing the temperature affect surface tension?
  2. You could try making boats with other materials to see if surface tension is powerful enough to propel bigger objects.
  3. You could try using oil instead of water for the experiment to investigate the surface tension of oil.

Class XII 12th Physics Project for 2009 Exams !

July 29, 2008
{ Click on the Title to see the Full Project }

Using a Laser Pointer to Measure the Data Track Spacing on CDs and DVDs

Investigating the ‘Mpemba Effect': Can Hot Water Freeze Faster than Cold Water?

Simple Harmonic Motion in a Spring-Mass System*

Distance and Constant Acceleration

Going the Distance: Launch Angles & Projectile Trajectory

Measuring the Surface Tension of Water

How Does Color Affect Heating by Absorption of Light?

The Joly Photometer: Measuring Light Intensity Using the Inverse Square Law

Solid Motor Rocket Propulsion

How the Strength of a Magnet Varies with Temperature*

What’s the Fastest Way to Cool a Soda?

Build a Motorboat Powered by Surface Tension








Follow

Get every new post delivered to your Inbox.

Join 38 other followers