Ears

Scientists are interested in the speed of sound, according to NASA, because it indicates the speed of molecules  transmitting a "small disturbance" (another way of describing a sound wave) through a gas medium.Transmission disturbance happens when a molecule in gas hit each other.  

 

    

Sound travels slowest through air because molecules that create air are far apart. Because they are far, the molecules take a longer time to collide with each other. The collision between molecules is what makes sound. Solids have molecules that are very close to each other so they transmit sound very fast. Liquids have molecules that are further apart than solids but closer to each other than gases. Sound cannot travel through a vacuum because there are no molecules in a vacuum.
Source: http://www.physlink.com/education/askexperts/ae20.cfm

2. I will answer question from Katie about "Are our ears sensitive?" (form)
Our ears are fragile and sensitive. They can get damaged by hearing loud noises. Ears can get damaged over time if they hear noises that are 85 dB (decibels) or more. If you hear sound at 85 dB for 8 hours, your ear can get damaged. But, if you hear 115 dB, it only takes about 30 seconds until the ear gets damaged. Your ears get damaged because sound gets delivered to hair cells. Those hair cells have stereocilia. The stereocilia rocks back and forth when exposed to sound. If you hear noises that are too loud, they make the stereocilia bend/break which makes them die and never grow back again.
Source: http://dangerousdecibels.org/education/information-center/decibel-exposure-time-guidelines/ , http://dangerousdecibels.org/virtualexhibit/2howdowehear.html

3. I will answer question from Ibu Primi about "What is the function of light in our daily life?" [function]
The function of light is to see. We see because light bounces off an object and we can see the light that bounces off the object. We can't see the light that the object absorbs. Example: We see an apple. It is red not because the apple is red, but because the light that bounces off it is red. If there is no light, we wouldn't be able to see anything.
Source: Christophe's presentation

4. I will answer question from Katie about "Why do we need to protect our ears?"(responsibility)
We need to protect our ears because if you get hearing loss, you will never get your hearing back. We hear because sound waves go into your ear canal as vibrations until they reach the eardrum. The eardrum passes the​ vibrations through the middle ear bones (ossicles) into the cochlea. Inside the cochlea, there are​ thousands of tiny hair cells. Hair cells change the vibrations into electrical signals that are sent to​ the brain through the hearing nerve. The brain tells you that you are hearing a sound and what that​ sound is.​ Each hair cell has a small patch of stereocilia. The stereocilia rocks back and forth when exposed to sound. If you hear noises that are too loud, they make the stereocilia bend/break which makes them die and never grow back again.
Source: http://dangerousdecibels.org/virtualexhibit/2howdowehear.html

Ear infections can be chronic or acute.

Acute ear infections are painful but short in duration.
https://www.healthline.com/health/ear-infections