Grade 8 SCIENCE SOUND

11/03/15

Sounds

• Listening to music, talking to your phone, or any other of that kind produces sound. Sound isn't just used as a transfer of energy but, also as a form of entertainment.
• Iphone,Ipad,Smartphone,Mp3, Mp4, MP5, and so on, all produce sounds mostly for entertainment.
• The science of sound has gone all the way from transferring energy to the creation of tunes and other things.
• In the field of Geology, sound is used to determine ocean depths.
• Health science used sounds for medical purposes i.e. Ultrasound

In this module you will learn about sounds and its components. 

11/17/15

Sound Propagation

     Sound consists of waves of air particles. Generally, sound propagates and travels through air. It needs a medium to propagate, and is considered as mechanical wave. In propagating sound, waves are characterized by longitudinal waves. Sound needs to be propagated in order for its waves to travel into the air.

Activity I

Objectives:

·         After the activity, you will learn that sounds consist of vibrations that travel through air.

Materials

·         1 rubber band

·         1 piece of plastic sheet

·         1 empty large can of powdered milk - 800 g

·         1 wooden ruler

·         1 empty small can of evaporated milk - 400 mL

·         rock salt

·         1 dowel or 1 wooden rod

·         1 blue bead

·         4 colored beads

·         3 inches of tape

·         2 large books

·         scissors

·         5 pieces of string

·         paper

·         transistor radio

·

Procedure:

Propagating Sound

o   Prepare the materials needed for the activity.

o   Put plastic tightly over the open end of the large

o   Put water on the plastic tightly over the open end of the large can, while putting a rubber band with it.

o   Put water on the plastic and sprinkle salt in it.

§  Tap the side of the can and observe.

·         You will see that the salt moves.

·         Tap different sides of the can then observe.

o   You will see that the salt nearest to the tap will move the most.

·         Sound made the salt bounce around.

o   Put a transistor radio or speaker near the can then turn its volume louder.

·         More sound, more movement

·         Sound waves affect the movement of the salt.

Transmitting sound

1.  Place the dowel on top of two books standing up.

2.  Tape the multiple balls with strings and hang them on the dowel.

3.  Tap the first ball and observe.

4.  Continue tapping then observe.

a.  The more you tap, the faster the balls move.

11/24/15

Activity 2: Characteristics of Waves: Comparing Longitudinal and Traverse waves

At the end of the activity, you will be able to:

1. Distinguish the different characteristics of waves;

2. Determine their frequency and wavelength; and

3. Compute the wave speed based on the frequency and wavelength

Materials:

·         Pentel pen or permanent marker

·         Stopwatch or mobile phone

·         Meter stick

·         Old calendar (big poster calendar) or old newspaper

·         Metal slinky

·         Compression rarefaction

Procedure:

·         Place the old newspaper or calendar and make sure it accommodates the size of the slinky.

·         Hold one end of the slinky and a partner on the other.

·         Mark the sides as reference points.

·         Shake the newspaper and make sure the reference point stays with the slinky.

·         Trace the wave form then measure the wavelength of the wave pulses.

·         Pull and push the slinky and observe.

·         Mark the areas of where the slinky shakes.

·         Count the number of compressions passing through point A in a minute.

When there are more waves passing through the reference point in a period Of time, which wave characteristic also increases?	Frequency
When there are more waves passing through the reference point in a period Of time, what happens to the wavelength of the waves?	The wavelength decreases

Different Kinds of Waves
Longitudinal Waves	In a transverse wave, the movement of particles is perpendicular to the direction of wave travel.
Transverse Waves	In a longitudinal wave, on the other hand, travel is parallel to the movement of the particles. In longitudinal waves, compressions are created when a push is applied on air. When air is pushed, there is a force applied on a unit area of air.

12/8/15

Activity 3: Sound Race… Where does sound travel fastest?

Objectives:

You will figure out what material sound travels best.

Materials

·         Ticking Clock

·         Mobile Phone

·         Wooden Dowel

·         Metal Rod

·         1-meter String

·         Carrying Case

Procedure

1.  Hold a ticking watch/clock as far away from your body as you can. Observe whether or not you can hear the ticking.

2.  Press one end of the wooden dowel against the back part of the watch and the other end beside your ear. Listen very well to the ticking sound. Record your observations.

3.  Repeat step #2 using a metal rod instead of the wooden dowel. Record your observations.

o   You would still hear the clock tick, no matter what materials you used.

4.  At the center of the meter long string, tie the handle of the metal spoon.

5.  Hold the string at each end and knock the spoon against the table to make it ring or to create a sound.

o   The solids are a much better carrier of sound.

6.  Listen to the ringing sound for a few seconds then press the ends of the strings against your ears.

7.  Observe and record the difference in sound with and without the string pressed against your ear.

o   The vibrations seemed louder through the string.

Activity 4: Chimes

Objectives:

At the end of the activity, you will be able to infer using improvised chimes that closely spaced materials are the best transmitters of sound.

Materials:

·         Materials for chime

·         Nylon string or thread

·         Plastic lid or wood about 1 ½ foot long

·         Small electric fan

·         Scissors

·         Nail and hammer

·         Beads

·         Paint

·         Iron stand

Procedure:

1.  Improvised Chime

a.  Go on a treasure hunt and look for items that will create a lovely sound when they collide, such as seashells, bells, beads, spoons, forks, and stones.

b.  If the items are thin enough, poke a hole through them with a nail. Then pull a piece of string or nylon thread through each hole, and tie a knot.

c.  For heavier objects, such as stones, spoons, or forks; wrap the string around the object a few times, and rub non-toxic liquid glue over the string to hold it in place.

d.  Next, find a colorful plastic lid or a nice looking pieces of wood to serve as the top of the wind chime.

e.  Tie at least 6 of these stringed objects on the plastic lid or on the wood.

f.  Make sure that the strands are evenly spaced and are not too far apart from each other.

g.  Finally, tie another string at the two ends of the plastic lid or on the wood for hanging the chime.

g.

2.  Sounding the Chimes

a.  Hang your chime in an iron stand where there is no wind source except your handy fan.

b.  The more closely distanced the stringed objects in the chime, the better the sound is transmitted.

The speed of sound may differ for different types of solids, liquids, and gases. For one, the elastic properties are different for different materials. This property (elastic property) is the tendency of a material to maintain its shape and not deform when a force is applied to the object or medium. Steel for example will experience a smaller deformation than rubber when a force is applied to the materials. Steel is a rigid material while rubber can easily deform and is known as a flexible material.

At the molecular level, a rigid material is distinguished by atoms and/or particles with strong forces of attraction for each other. Particles that quickly return to their rest position can vibrate at higher speeds. Thus, sound can travel faster in mediums with higher elastic properties (like steel) than it can through solids like rubber, which have lower elastic properties. Does the phase of matter affect the speed of sound?

It actually has a large impact upon the elastic properties of a medium. Generally, the bond strength between particles is strongest in solid materials and is weakest in gases. Thus, sound waves travel faster in solids than in liquids, and faster in liquids than in gases. While the density of a medium also affects the speed of sound, the elastic properties have a greater influence on wave speed. Among solids, the most rigid would transmit sound faster.

Activity 5: Faster sound, hotter or cooler?

Objective:

·         At the end of the activity, you will be able to determine how temperature affects the speed of sound.

Materials:

·         3 pieces 1000 ml graduated cylinders or tall containers

·         Thermometer

·         Bucket of ice

·         Electric heater or alcohol lamp

·         Tuning fork

Procedure:

Hot water	Normal water	Cold water
Louder sound	Normal sound	Low sound
More pitch	Moderate pitch	Low pitch
More frequency	Normal frequency	Low frequency
Faster Transmission	Normal Transmission	Slow Transmission

The hotter the medium the faster the sound travels. Heat just like sound is a form of kinetic energy. At higher temperatures particles have more energy (kinetic) and thus vibrate faster. And when particles vibrate faster there will be more collisions per unit time. With more collisions per unit time energy is transferred more efficiently resulting in sound traveling quickly.
In equation:	V= 331 m/s + 0.6 m(s)/C = (T)

Reflection of Sound

Just like any other wave, sound also exhibits reflection. Reflection is usually described as the turning back of a wave as it hits a barrier. Echo is an example of a reflected sound. Reverberation on the other hand refers to the multiple reflections or echoes in a certain place. A reverberation often occurs in a small room with height, width, and length dimensions of approximately 17 meters or less. Echo sounding is another application of sound reflection. This is used by scientists to map the sea floor and to determine the depth of the ocean or sea. This is just the same as how bats use sound to detect distances.

Refraction of Sound

When sound propagates in air, where the temperature changes with altitude, sound bends towards the hotter region. In this case, refraction happens. The refraction is due to the different refractive indices of air because of the difference in temperature. Day   – Hot temperature affects the speed of sound and changes to higher altitude. Night – Cold temperature affects the speed of sound and changes to lower altitude.

Activity 6

Reflecting and refracting sound

Objective:

At the end of the activity, you will be able to observe how longitudinal waves reflect and refract.

Materials:

·         metal slinky (large coil)

·         metal slinky (small coil)

Procedure

1.  Connect the fixed end to a wall or post. Make or create longitudinal waves by pushing and pulling the movable end part.

2.  Observe the longitudinal waves as the waves hit the wall or post. Record your observations.

a.  The compressions or rarefactions bounce off after hitting the wall.

b.  Louder sound is observed.

3.  Note the positions of the compressions before they reach the post. Note also the locations or positions of the compressions after hitting the wall of the post.

a.  Sound will also bounce off when it strikes a fixed end or the wall.

4.  Do this for 3 trials.