Page 25 - Casopis_PTV_3_pdf_flip
P. 25
Hravá stránka
YOUNG HISTORY: how people used to HOMEMADE HIFI: use a balloon to amplify sound
communicate - make a string phone Small sounds can still make a big noise when you use a good
Step back in time and use some old fashioned technology to sound conductor. Experiment with a balloon, compressed air
make a string phone while learning about sound waves with and your own ears to find out how it works and the science be-
this fun science project for children. hind it.
What you need: What you need:
• 2 paper cups • Balloon (1 + spare ones in case of an accident ;-))
• a sharp pencil or sewing needle to make holes What to Do:
• String (kite string and fishing lines work well) 1. Blow up the balloon.
What to Do: 2. Hold the balloon close to your ear while you tap lightly on
1. Cut a long piece of string, you can experiment with different the other side.
lengths but perhaps 10-20 metres is a good place to start. How it works:
2. Make a small hole in the bottom of each cup. Despite you only tapping lightly on the balloon your ears can
3. Thread the string through each cup and tie knots at each end hear the noise loudly. When you blew up the balloon you forced
to stop it pulling through the cup (alternatively you can use the air molecules inside the balloon closer to each other. Be-
a paper clip, washer or similar small object to hold the string cause the air molecules inside the balloon are closer together,
in place). they become a better conductor of sound waves than the ordi-
nary air around you.
4. Move into position with you and a friend holding the cups at Do you want to continue with the experiment? Try to answer
a distance that makes the string tight (making sure the string these questions:
isn't touching anything else). 1. Does it work with a basketball or soccer ball?
5. One person talks into the cup while the other puts the cup to 2. Does the size of the balloon affect the loudness?
their ear and listens, can you hear each other?
How it works: 3. Does the effect still work if you use earphones with music
Speaking into the cup creates sound waves which are converted instead of tapping ?
into vibrations at the bottom of the cup. The vibrations travel
along the string and are converted back into sound waves at the PLASTIC QUIZ: “She got her looks from her father.
other end so your friend can hear what you said. Sound travels He's a plastic surgeon! ” Groucho Marx
through the air but it travels even better through solids such as 1. A plastic is a material that can change its ………………
your cup and string, allowing you to hear sounds that might be a) temperature b) age c) shape
too far away when traveling through the air.
FOOD: How to make chocolate bars 2. What are most plastics made from?
– number the sentences in order a) coal b) oil c) gas
1. People take the seed pods/beans from the cocoa/cacao tree. 3. To make a plastic product, machines put hot plastic in a …….
… Machines grind and heat the seeds. a) dishwasher b) mold c) paper box
… Sugar and milk is cooked with the liquid.
4 What can plastic bottles be recycled into?
a) clothes b) water pipes c) both a) and c)
… People leave the seed pods in the sun. 5. Long-chain molecules, either synthetic or natural, made by
… They put the liquid in molds to make chocolate bar. bonding many smaller molecules are called:
a) plastics b) polymers c) monomers
… They throw away the outside and keep seeds. 6. Examples of natural polymers are:
… Each cocoa tree yields 20-30 pods per year. It takes the whole a) nylon and polyester b) polythene and PVC
c) proteins and silk
year's crop from one tree to make 450gms of Chocolate.
… Then seeds become liquid. Gymnázium, základní škola a mateřská škola Hello s. r. o.
ACCENDO – Centrum pro vědu a výzkum, o. p. s.
25
YOUNG HISTORY: how people used to HOMEMADE HIFI: use a balloon to amplify sound
communicate - make a string phone Small sounds can still make a big noise when you use a good
Step back in time and use some old fashioned technology to sound conductor. Experiment with a balloon, compressed air
make a string phone while learning about sound waves with and your own ears to find out how it works and the science be-
this fun science project for children. hind it.
What you need: What you need:
• 2 paper cups • Balloon (1 + spare ones in case of an accident ;-))
• a sharp pencil or sewing needle to make holes What to Do:
• String (kite string and fishing lines work well) 1. Blow up the balloon.
What to Do: 2. Hold the balloon close to your ear while you tap lightly on
1. Cut a long piece of string, you can experiment with different the other side.
lengths but perhaps 10-20 metres is a good place to start. How it works:
2. Make a small hole in the bottom of each cup. Despite you only tapping lightly on the balloon your ears can
3. Thread the string through each cup and tie knots at each end hear the noise loudly. When you blew up the balloon you forced
to stop it pulling through the cup (alternatively you can use the air molecules inside the balloon closer to each other. Be-
a paper clip, washer or similar small object to hold the string cause the air molecules inside the balloon are closer together,
in place). they become a better conductor of sound waves than the ordi-
nary air around you.
4. Move into position with you and a friend holding the cups at Do you want to continue with the experiment? Try to answer
a distance that makes the string tight (making sure the string these questions:
isn't touching anything else). 1. Does it work with a basketball or soccer ball?
5. One person talks into the cup while the other puts the cup to 2. Does the size of the balloon affect the loudness?
their ear and listens, can you hear each other?
How it works: 3. Does the effect still work if you use earphones with music
Speaking into the cup creates sound waves which are converted instead of tapping ?
into vibrations at the bottom of the cup. The vibrations travel
along the string and are converted back into sound waves at the PLASTIC QUIZ: “She got her looks from her father.
other end so your friend can hear what you said. Sound travels He's a plastic surgeon! ” Groucho Marx
through the air but it travels even better through solids such as 1. A plastic is a material that can change its ………………
your cup and string, allowing you to hear sounds that might be a) temperature b) age c) shape
too far away when traveling through the air.
FOOD: How to make chocolate bars 2. What are most plastics made from?
– number the sentences in order a) coal b) oil c) gas
1. People take the seed pods/beans from the cocoa/cacao tree. 3. To make a plastic product, machines put hot plastic in a …….
… Machines grind and heat the seeds. a) dishwasher b) mold c) paper box
… Sugar and milk is cooked with the liquid.
4 What can plastic bottles be recycled into?
a) clothes b) water pipes c) both a) and c)
… People leave the seed pods in the sun. 5. Long-chain molecules, either synthetic or natural, made by
… They put the liquid in molds to make chocolate bar. bonding many smaller molecules are called:
a) plastics b) polymers c) monomers
… They throw away the outside and keep seeds. 6. Examples of natural polymers are:
… Each cocoa tree yields 20-30 pods per year. It takes the whole a) nylon and polyester b) polythene and PVC
c) proteins and silk
year's crop from one tree to make 450gms of Chocolate.
… Then seeds become liquid. Gymnázium, základní škola a mateřská škola Hello s. r. o.
ACCENDO – Centrum pro vědu a výzkum, o. p. s.
25
