Systems & Inquiry

Open and Closed Systems: It’s a MATTER of inputs and outputs

When you hear the word, “system,” what words or images come to mind? Examples that come to mind……solar system, digestive system, school system, stereo system, respiratory system, and muscular system A system is made up of different parts that come together to form a whole; a system is a collection of things and processes that interact to perform some function. What’s a SYSTEM?

Why do we use systems? The world around us is so complex. To study everything all at once in its entirety would be impossible and overwhelming….. So scientists break things down into smaller related parts that they can study more easily and we call these things systems….

Systems are similar because they are made up of several parts; if one of these parts changes, it impacts the entire system. However the purpose of the systems, and their inputs and outputs, are different depending upon what you are studying. SYSTEM INPUT: Any energy or matter that comes into a system SYSTEM OUTPUT: Any energy or matter that leaves a system is an output and a product of a system.

We know about inputs and outputs inputs—things that get put in to make the system function (not a part of the system). outputs—stuff that gets put out of a system, sometimes what they do, and sometimes other things (not a part of the system).

What kind of energy input is needed by these systems?

Reminder: Inputs In order to carry out their purpose, systems need an input of some kind of – Energy – Matter – Information.

Remember: Forms of Energy Input There are lots of kinds of energy. Some common kinds are: ElectricalSound Thermal (heat)Light Mechanical Nuclear Chemical (food is one example; a battery is another)

What kind of output is produced by these systems?

Reminder: Outputs Outputs from a system can include – Energy – Matter – Information.

Remember: outputs can become inputs Sometimes the output from one system can become the input for another system. Repeated image from second PowerPoint of dog with ears blown back by fan. Repeated from second PowerPoint—image of woman listening to iPod through headphones.

That Brings Us to Open and Closed Systems We can describe systems as being open or closed. Closed Coke can.

Open vs. Closed Systems In open systems matter and energy may flow in and out of the system. In closed systems only energy flows in or out… the amount of matter stays the same.

Open Systems An open system is a system in which both matter and energy can enter and leave. Information can also enter and leave. What kinds of energy are inputs and outputs for this system? What kinds of matter are inputs and outputs?

Closed Systems In a closed system, matter cannot enter and leave. Only energy and information can. What kinds of energy can enter and leave this system? Why can matter not enter or leave?

Subsystems A subsystem is a system that is part of another system. It’s a system within a system.

Subsystems

How do we find the boundaries of a system? The boundaries of a system is determined by the question you ask and how the systems parts work together? Example: The bicycle….seat, frame, wheels, brakes, lights etc… it’s all one physical part together…if you take away one wheel now it’s a unicycle not a bike…. The boundaries define the system and what your studying.

Boundaries can change Boundaries can physically change, like when part of a forest is cut down We can change boundaries when we want to think about just part of a system. For example, a doctor might consider your whole body system to see if you are healthy overall, or just look at your throat if you have a sore throat.

How can systems change? When their boundary changes, they can become open or closed.

Changing Boundaries Example

Physical Boundary Change Picture of forest with road through it.

Closed can become open; open can become closed Example: The closed system becomes open when an opening is created in the actual physical boundary.

Closed can become open; open can become closed Plants are open systems. They have parts to help them survive. They take in light energy, plus matter (water and carbon dioxide and minerals) and give out matter (oxygen, new growth, leaves, fruit).

Closed can become open; open can become closed But if we expand our boundary to include the whole mini ecosystem that the plant is a part of, we are looking at a closed system. No matter can leave or enter the bottle ecosystem, though light and heat energy can. Completed ecosystem in a bottle from science kit.

Stump a friend Take a minute and think of an example of a system that is open or closed. Why do you think it is open or closed? Now, ask your friend about your system. Do they agree or disagree? How can you decide who is correct?

Why use systems? Because the universe is complex and gigantic. So, scientists break things into smaller units they call “systems”. That way, they don’t have to try to study everything at once. They can look at it system by system—or systematically.

Solar system image repeated from second PowerPoint.

Repeated image of Earth from space from PowerPoint 2.