How Do Airbags Work and Can They Really Kill You? Chemistry of Cars Ep.2

Summary

In this episode of 'The Chemistry of Cars', Charlotte Redcap explores the science behind airbags, answering the question of whether they can be lethal. She explains the evolution of airbag technology from its invention by John W. Hetrick to modern safety features. Redcap delves into the chemical components of airbags, including sodium azide, potassium nitrate, and silica, detailing how they react to produce gas for rapid inflation. She also discusses the engineering process to calculate the amount of sodium azide needed for safe deployment, emphasizing the improvements in airbag safety over the years.

Takeaways

• 🎓 Charlotte Roadcap, the resident chemist at TFL Car, recently graduated with a bachelor's degree in chemistry from CU Boulder and is starting a new show about the chemistry of cars.
• 💡 The concept of airbags was invented by John W. Hetrick, a retired industrial engineer, who was inspired to protect his daughter from a sudden stop by using his knowledge of compressed air from torpedoes.
• 📜 John Hetrick patented the airbag system in 1952, but it wasn't until the late 1980s that airbags became a common feature in cars due to challenges in timing and crash detection.
• 🚗 The first consumer car available with airbags was the 1974 Oldsmobile Toronado, where airbags were offered as an optional feature, not standard.
• 🛡 Inside an airbag, there are three chemical components: sodium azide, potassium nitrate, and silica, which react to produce a large amount of gas for inflation.
• 🔬 The chemical reaction within an airbag is initiated by a sensor that triggers a wire filament to heat up and decompose sodium azide into sodium and nitrogen gas.
• 🔄 The produced sodium is then mixed with potassium nitrate to form potassium oxide and sodium oxide, which, when mixed with silica, create a harmless alkaline silicate glass.
• 🧪 The amount of sodium azide needed in an airbag can be calculated through mechanical analysis, taking into account the desired pressure and the volume of the airbag.
• 🚀 Airbags inflate extremely rapidly, within 30 milliseconds, to provide protection during a collision.
• ⚖️ The force and pressure required to inflate an airbag are calculated based on the mass of the airbag, the acceleration, and the area over which it expands.
• ❗ Airbags can be lethal if not designed properly, as they deploy at high speeds and with significant force, but modern airbags have sensors to adjust inflation to the occupant's size for safety.

Q & A

Who is the host of the 'Chemistry of Cars' show?

The host of the 'Chemistry of Cars' show is Charlotte Roadcap.

What is the primary focus of the 'Chemistry of Cars' show?

The primary focus of the 'Chemistry of Cars' show is to explore the chemistry behind various aspects of cars, starting with the topic of airbags.

What is the big question Charlotte addresses in the script about airbags?

The big question Charlotte addresses is whether airbags can kill you, and she confirms that they can, but also discusses the advancements made by automakers to prevent such incidents.

Who is credited with the initial idea of the airbag?

John W. Hetrick is credited with the initial idea of the airbag, inspired by an incident where he and his wife instinctively protected their daughter from a potential car crash.

What year did John Hetrick patent the airbag system?

John Hetrick patented the airbag system in 1952.

What were the main difficulties that delayed the widespread availability of airbags in cars?

The main difficulties that delayed the widespread availability of airbags were issues with timing and crash severity detection.

Which was the first consumer car available with airbags?

The first consumer car available with airbags was the 1974 Oldsmobile Toronado, where they were offered as an option, not as a standard feature.

What are the three chemical components found inside an airbag?

The three chemical components found inside an airbag are sodium azide, potassium nitrate, and silica.

How does the chemical reaction in an airbag produce gas?

The chemical reaction in an airbag produces gas by heating a wire filament which decomposes sodium azide to form sodium and nitrogen gas. The sodium produced is then mixed with potassium nitrate to form potassium oxide and sodium oxide, which react with silica to form a harmless alkaline silicate glass.

What is the role of the wire filament in the airbag's chemical reaction?

The wire filament's role in the airbag's chemical reaction is to heat up and initiate the decomposition of sodium azide, which is the first step in producing the gas that inflates the airbag.

How is the amount of sodium azide needed for an airbag calculated?

The amount of sodium azide needed for an airbag is calculated through a mechanical analysis that considers the desired pressure inside the airbag, the volume it needs to expand to, and the ideal gas law at room temperature.

What is the maximum pressure inside an airbag during inflation?

The maximum pressure inside an airbag during inflation is about five pounds per square inch.

How do modern airbags adjust to the occupant's size?

Modern airbags can adjust inflation speed and pressure based on the occupant's size using sensors in the seats that detect weight and adjust the inflation accordingly.

What is the potential danger of the sodium produced in the airbag's chemical reaction?

The potential danger of the sodium produced in the airbag's chemical reaction is that sodium by itself is extremely dangerous to humans, so it needs to be mixed with potassium nitrate to form a safer compound.

Outlines

00:00

🚗 The Chemistry of Airbags

Charlotte Redcap introduces 'The Chemistry of Cars' show, focusing on the chemistry behind airbags. She discusses the history of airbags, starting with John W. Hetrick's invention inspired by a near-accident with his daughter. The evolution of airbags from their first appearance in the 1974 Oldsmobile Toronado to their widespread use in the late 80s is covered, with a focus on the challenges in timing and crash detection. The paragraph also delves into the chemical components of airbags, including sodium azide, potassium nitrate, and silica, and how they react to produce gas for inflation. The chemistry of airbag deployment is simplified, explaining the heat-triggered decomposition of sodium azide and subsequent reactions that produce a safe, glass-like substance to protect passengers.

05:01

🔍 The Science Behind Airbag Inflation

This paragraph delves into the mechanical analysis required to determine the speed and force of airbag inflation. It explains how the airbag needs to inflate rapidly to meet the driver's face before impact, using basic physics equations to calculate acceleration and force. The force exerted by the inflating airbag is quantified, leading to the calculation of the necessary pressure to safely deploy the airbag. The ideal gas law is applied to determine the amount of chemical reactants needed for the airbag to reach the desired pressure and volume. The paragraph concludes with a discussion on the potential dangers of airbags, such as the force of the deploying bag, and modern innovations that adjust airbag inflation based on occupant size and weight for enhanced safety.

Keywords

💡Airbag

An airbag is a safety device found in vehicles that rapidly inflates to cushion and protect passengers during a collision. In the video, the theme revolves around the chemistry and engineering behind airbags, explaining how they were invented to prevent injury by providing a cushioned barrier between the passengers and the vehicle's interior.

💡Charlotte Roadcap

Charlotte Roadcap is the resident chemist and host of the 'Chemistry of Cars' show. She introduces the topic of airbags, their history, and the chemical reactions involved in their deployment. Her role is central to the educational narrative of the video.

💡John W. Hetrick

John W. Hetrick is credited with the invention of the airbag. The script mentions his inspiration for the airbag came from an incident involving his daughter and the desire to protect her during a sudden stop. His name is significant as it represents the origin of the airbag technology discussed in the video.

💡Sodium Azide

Sodium azide is a key chemical component in airbags. The script explains that it decomposes under heat to produce sodium and nitrogen gas, which rapidly inflates the airbag. It is an example of the chemistry involved in airbag deployment and is crucial to understanding the safety mechanism.

💡Potassium Nitrate

Potassium nitrate is another chemical used in airbags to help neutralize the reaction of sodium azide. It reacts with the sodium produced to form potassium oxide and sodium oxide, reducing the risk of harm to passengers by transforming the reaction products into a safer form.

💡Silica

Silica is used in conjunction with potassium oxide and sodium oxide to form alkaline silicate glass, a harmless white powder. This process is part of the chemical reactions within the airbag that ensure the safety of passengers by converting potentially harmful substances into an inert form.

💡Inflation Speed

Inflation speed refers to how quickly an airbag deploys during a collision. The script describes the airbag inflating within 30 milliseconds, emphasizing the rapid response required for effective protection, which is a critical aspect of airbag technology.

💡Force and Pressure

Force and pressure are physical concepts explained in the script to calculate the amount of sodium azide needed for airbag deployment. Force is calculated as mass times acceleration, and pressure is force per unit area, which helps determine the necessary chemical reaction to achieve the desired airbag inflation.

💡Ideal Gas Law

The Ideal Gas Law is a fundamental principle in chemistry and physics that relates the pressure, volume, and temperature of an ideal gas. In the context of the video, it is used to calculate the amount of gas produced by the chemical reaction in the airbag, which is essential for understanding the deployment process.

💡John P. Nolan

John P. Nolan is mentioned as the chemist who invented the chemical reaction process used in airbags. His work is integral to the video's narrative as it illustrates the scientific innovation behind airbag technology and its contribution to vehicle safety.

💡Occupant Size Detection

Occupant size detection is a modern feature of airbag systems that adjusts the inflation speed and pressure based on the passenger's size. The script highlights this as an example of how airbag technology has advanced to provide customized safety measures, enhancing the overall theme of innovation in car safety.

Highlights

Introduction to the new show 'The Chemistry of Cars' hosted by Charlotte Roadcap, focusing on the chemistry behind airbags.

Airbags can be lethal, but modern engineering has significantly reduced this risk.

John W. Hetrick's inspiration for the airbag came from a near-accident with his family, leading to his 1952 patent.

The first consumer car with airbags was the 1974 Oldsmobile Toronado, available as an optional feature.

Airbags contain sodium azide, potassium nitrate, and silica, which chemically react to produce gas for inflation.

The chemical reaction within an airbag occurs in about 30 milliseconds, involving the decomposition of sodium azide under heat.

Sodium produced in the reaction is dangerous, so it's combined with potassium nitrate to form a safer compound.

The final reaction product is alkaline silicate glass, a harmless white powder.

John Petes is credited with the invention of the chemical process used in airbags.

A simple mechanical analysis is used to calculate the amount of sodium azide needed for airbag inflation.

The airbag inflates at an acceleration of 13,300 meters per second squared to meet the driver's face before impact.

The force exerted by the inflating airbag is calculated to be 33,300 newtons.

The pressure needed to inflate the airbag is derived from the force exerted, resulting in 0.3 atmospheres.

Absolute pressure is calculated by adding atmospheric pressure to the gauge pressure inside the airbag.

The ideal gas law is used to calculate the amount of sodium azide required for the airbag to save a life.

Modern airbags can adjust inflation speed and pressure based on occupant size, improving safety.

Despite advancements, airbags can still cause serious injury due to the force of a 2.5-kilogram bag traveling at high speeds.

Charlotte Roadcap invites viewers to suggest more chemistry of cars projects in the comments.

Transcripts

hi everyone and welcome to tfl car my

name is charlotte roadcap and i am the

resident chemist here at tfl um i

graduated my bachelor's degree in

chemistry about two weeks ago from cu

boulder pretty excited about it now

using that knowledge we decided to start

a very cool new show called the

chemistry of cars and today is all about

airbags

the big question on everyone's mind when

it comes to airbags is can it kill you

yes yes it can however automakers have

come very very far since the early days

of airbags and have engineered all kinds

of awesome ways to make sure

that they don't

the story of the airbag begins with john

w hetrick who was a retired industrial

engineer one day him and his wife were

driving down a country road with their

seven-year-old daughter in the bench

seat right between them and what

happened was they came up over the crest

of a hill and in the middle of the road

was a giant rock so basically the

reaction that john and his wife both had

was to instinctively put their arm out

where their daughter was sitting in the

middle of them to prevent her from

flying forward and hitting the dashboard

when mr hetrick got home the first thing

he did was go straight to his drawing

board and think hey how can i solve this

problem he thought back to 1944 when he

was a naval engineer and there was an

accidental release of a torpedo now

those torpedoes were powered by

compressed air so this compressed air

system was the forerunner of today's

arabic mr hetrick patented the system in

1952 and as you know you know airbags

weren't really available until the late

80s as a common feature on cars so why

the gap

well basically difficulties in timing

and crash severity detection

were the cause

the first consumer car ever available

with airbags was the 1974 oldsmobile

toronado and they came actually not as

standard but as an option for 225

[Music]

inside your airbag you have three

different chemical components you have

sodium azide you have potassium nitrate

and then you also have silica and we're

going to figure out how those come

together to produce a whole lot of gas

so here's what happens all within

remember 30 milliseconds and it's pretty

darn crazy so the simplest way to

explain a sensor now there's all kinds

of different types but the most simple

one is basically a magnet holding a

metal ball if this is the front of your

car and you're moving forward however

you stop suddenly this ball is going to

go forward

and trigger

this circuit and when you come around

it's going to heat that little wire

filament up and cause that chemical

reaction to happen basically what

happens is a little

wire filament heats up sodium azide now

sodium azide is very stable under you

know room temperature however under heat

it decomposes to form

sodium

just the metal

and

nitrogen gas you've produced a whole lot

of gas however you've also produced a

whole lot of sodium and sodium by itself

is extremely dangerous as far as humans

go so the way you want to get rid of

that is taking the sodium that was

produced in the first reaction and

mixing it with potassium nitrate and

then producing

potassium oxide

sodium oxide

and

nitrogen gas again so again you know you

kind of want to make these little

harmful fellows a bit more friendly to

the person that's going to be flying

forward in the airbag so what you want

to do is you want to take your potassium

oxide mix it with your sodium oxide that

was produced in this reaction and then

also miss it mix it with silica and then

you're going to get something called

alkaline

silicate glass

which is basically just a simple white

powder and it's not going to hurt you so

the chemist who invented all of this his

name was john petes

so if i was a chemist working on an

airbag and i wanted to figure out how

much sodium azide i would need to make

this pressure of five pounds per square

inch inside the airbag to catch your

head when you you know run into a light

post well this is how you do it through

a simple mechanical analysis these are

very simple equations now it should be

said that an actual airbag engineer

would be going through a many many many

many more steps than what we're going to

do here although you know this just

demonstrates a very cool proof of

concept that you can figure this out

the first thing you're going to want to

figure out when doing the simple

mechanical analysis is how fast you need

the airbag to inflate now the way that

you do that is just through a simple

approximation say you have this cylinder

here and it starts compressed as such

and then it grows 30 centimeters to come

meet the driver's face before impact to

find that acceleration what you're going

to use is just a very simple equation

acceleration equals final velocity minus

initial velocity both of those are

squared divided by 2 times the distance

that you need it to travel 13

300 meters per second squared and that's

basically just saying

that's extremely fast

so the next thing you're going to need

to figure out is force how much force is

this airbag expanding with well force is

equal to mass times acceleration so

again just simply plugging in the

numbers that we have you have a 2.5

kilogram airbag multiplied by your crazy

fast acceleration of 13

300 meters per second squared and you

get 33

300 newtons and just for those who

aren't very familiar with units

newtons is just a simple measure of

force from acceleration we found force

and from force we can find the pressure

needed to inflate the air bag so

pressure is equal to force divided by

area so we take the force that we found

above which is 33

300 newtons and then just simply divide

it by the area of your airbag which is

approximately you know 8

756 centimeters squared for a 60 liter

airbag and then that is equal to 0.3

atmospheres so we found this pressure

right one third of an atmosphere what

what does that mean exactly well

basically let's put it like this that's

something called gauge pressure let's

compare this to when you check the tire

pressure on your car you have your

little gauge and then you pop there's a

little fellow that pops up and it gives

you a reading of the pressure inside

your tire so

that

little guy that pops up is expanding

against atmospheric pressure so to find

the absolute pressure you have to take

the pressure

outside your car plus the pressure

inside your tire and then you get

absolute pressure so let's review what

we know we know that we need to create a

pressure of 1.3 atmospheres we know that

we need to expand this airbag to 60

liters we also know

that the temperature at which this is

going to be occurring at is room

temperature which when you convert it to

the temperature that the ideal gas law

needs to be calculated with is 298

kelvin

so when you do all that simplistically

put you get 3.2 moles basically a mole

is a measure of how much chemical

substance there is that's all it is it's

just an amount of something if i have a

little jar of sodium azide and i'm

trying to figure out how much i need to

put in well basically all you do is you

take the number of moles that you need

and then you multiply it

by the weight

per mole

and then that is 3.2 times 65 grams per

mole

and then you get 138 grams of sodium

azide that i need to put in your airbag

to save your life

[Music]

going back to the question of can an

airbag kill you yes yes it can because

here's what's happening you have

something that weighs about 2.5

kilograms coming at you

at 150 to 200 miles per hour and that

creates an incredible force and that's

what causes serious injury now you might

be thinking well what about the pressure

inside the airbag that

plays a part but not so much because you

might think that it inflates to you know

like 40 50 100 psi but actually you want

it to be soft so it's maximum pressure

during inflation is only about five

pounds per square inch we have you know

airbags today that can adjust inflation

speed and the pressure to occupant size

so basically you have these little

sensors in your seats senses your weight

and then it can figure out you know

what's the ideal pressure for this to

inflate to which is pretty darn cool and

an excellent safety innovation

all right guys well thank you so very

much for watching i really enjoyed

making this as always and i can't wait

to make more so if you have any other

cool chemistry of cars projects for me

to accomplish leave them in the comments

below again i'm charlotte redcap thank

you so much for watching