Grade by Grade
D. Structures and Mechanisms · Systems in Action

What Is a System? Types of Systems

D2.1 A1.5About 40 minutes
Learning goals
  • I can explain what a system is, using the words components, purpose and subsystem.
  • I can identify mechanical, electrical, social, natural and information systems.
  • I can explain why many real systems are combinations of different types.
  • I can break a system into its subsystems.

Words to know

system
A group of parts that work together to do a job.
component
One part of a system. A bicycle's chain, pedals and brakes are components.
purpose
The job a system is designed to do.
subsystem
A smaller system inside a bigger system. A bicycle's braking subsystem is part of the whole bicycle.
mechanical system
A system of moving parts that transfer force and motion, like a bicycle or a can opener.
social system
A system of people, rules and organizations that work together to meet a need, like a school or public transit.
natural system
A system found in nature, like the human digestive system or a wetland ecosystem.

Hook: a snow day morning

It is a snowy January morning. At 6:00 your alarm clock rings. Your school board has already checked the roads with bus companies and posted on its website: buses are cancelled. A snowplow rumbles past. Your parent checks the weather app. You grab a shovel and clear the steps while your lungs, heart and muscles work hard.

Before breakfast you have used at least six different systems. In this unit you will learn to see the world as systems, and to ask how they work, how well they work, and how they affect people and the planet.

An orange snowplow truck pushes snow off a residential street on a snowy winter morning.
A snowplow is part of a big transportation system: trucks, drivers, salt, schedules and roads all work together. Can you name its inputs and outputs? AI-generated image

Remember from earlier grades

In Grade 4 you studied mechanisms: pulleys, gears and levers that change force, direction and speed. In Grade 7 you studied structures and how their parts carry loads. A system is a bigger idea. It can include structures and mechanisms, but also electricity, information, living things and even people and rules.

What is a system?

A system is a group of parts that work together to do a job.

  • Each part is a component.
  • The job is the system's purpose.
  • If you remove or break one component, the whole system may stop working well. A bicycle with no chain cannot move forward when you pedal, even though every other part is fine.

Big systems are often made of smaller systems called subsystems. A car has a braking subsystem, a steering subsystem, a fuel or battery subsystem and more. Each subsystem has its own job, and together they serve the car's purpose: moving people safely.

Type of systemWhat it is made ofExamples
MechanicalMoving parts that transfer force and motionbicycle, can opener, snowblower, elevator, sewing machine
Electrical / electronicParts that use electric currenthome wiring, a phone, a string of holiday lights, traffic signals
SocialPeople, rules and organizations meeting a needa school, a hospital, public transit, a food bank, a hockey league
NaturalLiving things and natural processes working togetheryour digestive system, a forest ecosystem, the water cycle
Information / communicationParts that collect, store or send informationthe internet, a library catalogue, a weather forecast service
Five common types of systems. Many real systems are combinations.

Most real systems are combinations

A city's snow-clearing system is a good example:

  • Social: the city decides which roads are cleared first (main roads, bus routes and hospital routes usually come first), hires and trains drivers and sets work shifts.
  • Mechanical: plows, blades, salt spreaders and snowblowers.
  • Information: weather forecasts, maps of routes and, in many cities, GPS trackers on the plows.
  • Natural: the snowfall itself and the temperature, which decide how much work is needed.

When you identify a system's type, look at what its main components are. If you see moving parts, it has a mechanical part. If you see people following rules, it has a social part.

City snow-clearingsystemSOCIALroads cleared first,drivers, shiftsMECHANICALplows, blades,salt spreadersINFORMATIONforecasts, route maps,GPS on plowsNATURALsnowfall andtemperature
One system, four types of parts. The snow-clearing system needs its social, mechanical, information and natural parts working together, which is why it is a combination system.
Worked example

Let's classify the parts of a school bus system

A school bus system gets students to school safely. Identify its mechanical, social and information parts.

  1. Mechanical: the bus itself, with its engine (or electric motor), wheels, axles, steering and brakes. Its stop-arm swings out when the bus stops.
  2. Social: the drivers, the routes and timetables, the rules (such as cars must stop for a bus with flashing red lights), and the people at the school board and bus company who decide when buses are cancelled.
  3. Information: the phone line, website or app that tells families about delays and cancellations, and the radio a driver uses.
  4. Conclusion: the school bus system is a combination system. Its purpose (getting students to school safely) needs all three parts.

Mechanical: the bus. Social: drivers, routes, rules and decision makers. Information: delay and cancellation notices, radios. It is a combination system.

Worked example

Let's break a bicycle into subsystems

Name three subsystems of a bicycle and the job of each.

  1. Look for groups of parts that do one job together.
  2. Drive subsystem: pedals, cranks, chain, gears and the back wheel. Job: turn your pushing into forward motion.
  3. Braking subsystem: brake levers, cables and brake pads (or discs). Job: slow and stop the bike.
  4. Steering subsystem: handlebars, the fork and the front wheel. Job: change direction.

Drive (move forward), braking (slow down and stop) and steering (change direction). All three serve the bike's purpose: moving a rider safely.

brake padbrake padbrake leverhandlebarsforkpedal + chainringchainDRIVEpedals, chain, gears,back wheel: go forwardBRAKINGlevers, cables, pads:slow down and stopSTEERINGhandlebars, fork,front wheel: turn
A bicycle broken into three subsystems. Each part is shaded the same as the subsystem it belongs to, and each subsystem has its own job in the bike's purpose: moving a rider safely.

Think like a scientist

When you describe a system, use the words components, purpose and subsystem. Instead of "the bike has stuff that makes it go", say "the drive subsystem's components, the pedals, chain and gears, transfer the rider's force to the back wheel". Clear words make your thinking clear (A1.5).

Just for fun

I have a chain but I have never been to jail. I have brakes but I never take a vacation. Take away one of my links and I stop working. What am I?

A bicycle: a system where every component matters.

Hands-on activity

System scavenger hunt

You need: paper, a pencil, about 20 minutes.

  1. Walk through your home (and look out the window). Find one example of each type: mechanical, electrical, social, natural and information.
  2. For each one, write its purpose and name three components.
  3. Pick the most interesting one and draw it as a labelled diagram. Circle any subsystems.
  4. Share your diagram with a family member and explain it in two or three sentences, using the words component, purpose and subsystem.

What to look for: examples might be a can opener or door hinge (mechanical), a lamp or router (electrical/information), your family's chore schedule or your school (social), a houseplant or your own body (natural). Each example has a clear purpose and real components, e.g. a lamp: purpose is to give light; components are the plug, cord, switch and bulb.

Your turn

1

What is a system?

2

What type of system is a food bank?

3

What type of system is a can opener?

4

Name two subsystems of the human body.

5

A string of holiday lights stops working when one bulb is removed. What does this show about systems?

6

Why is a hospital called a combination system?

7

What is the purpose of a traffic light system?

More practice: warm-up

1

What do we call one part of a system?

2

What do we call the job a system is designed to do?

3

Is a forest ecosystem a social system or a natural system?

4

Is a hockey league a mechanical system or a social system?

5

Name one mechanical system you used today.

More practice: on your own

1

Classify each as mechanical, electrical, social, natural or information: a) a snowblower b) a weather forecast service c) the water cycle d) a student council.

2

Name three subsystems of a car and the job of each.

3

Explain why a library is a combination system.

4

Your family has a weekly chore chart. Is it a system? Explain.

5

A bicycle chain falls off. Which subsystem has failed, and what can the bike still do?

Challenge

1

Choose a winter sport facility, such as an outdoor skating rink in a park. Identify at least one mechanical, one social, one natural and one information component, and explain how they work together.

2

A student says, "A system has to have moving parts." Use two examples to show this is not true.

3

Draw (or describe) a system diagram of your school as a system. Show at least four subsystems.

Check your understanding

Quiz

1.

What is a system?

2.

Which is a social system?

3.

The braking parts of a bicycle are best described as a...

4.

Which is a natural system?

5.

Why is a city snow-clearing system called a combination system?

6.

What is the purpose of a furnace system?

For parents and teachers

Big idea (D2.1): Grade 8 students identify various types of systems. A system is any group of components working together for a purpose. Help your child see that systems include not only machines but also social systems (schools, transit, health care) and natural systems (body systems, ecosystems), and that most real systems are combinations.

How to help: Name systems in daily life: "What kind of system is the grocery store checkout? What are its components?" Ask your child to explain using the words component, purpose and subsystem (A1.5, communicating with science vocabulary).

Common difficulties:

  • Thinking a system must be mechanical or electronic. Point out that a family's routine or a sports league is also a system.
  • Naming parts without saying the purpose. Always ask "What is the job of the whole system?"
  • Not seeing subsystems. Ask, "Which parts work together on one smaller job?"