energy transfer

Energy Transfer

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What is Energy?

• (physics) the capacity of a physical system to do work; the units of energy are joules or ergs; "energy can take a wide variety of forms"

• Work: When a force acts to move an object, we say that Work was done on the object

Thermodynamics is the study of energy.

• First Law of Thermodynamics: Energy can be changed from one form to another, but it cannot be created or destroyed. The total amount of energy and matter in the Universe remains constant, merely changing from one form to another.

• The Second Law of Thermodynamics states that "in all energy exchanges, if no energy enters or leaves the system, the potential energy of the state will always be less than that of the initial state." This is also commonly referred to as entropy.

• E.X. A watchspring-driven watch will run until the potential energy in the spring is converted, and not again until energy is reapplied to the spring to rewind it. A car that has run out of gas will not run again until you walk 10 miles to a gas station and refuel the car.

LAW

• In physics, the law of conservation of energy states that the total amount of energy in any isolated system remains constant but cannot be recreated, although it may change forms, e.g. friction from rubbing your hands together turns kinetic energy into thermal energy.

Two Types of Energy

• Potential Energy: Potential energy can be thought of as energy stored within a physical system

• Kinetic Energy: Kinetic energy is the energy of motion. An object which has motion - whether it be vertical or horizontal motion

5 Forms Of Energy(there are many forms but these will do for our purposes.)

• Solar

• Thermal

• Mechanical

• Electric

• Chemical

Solar

• Solar energy is energy directly from the Sun.

Thermal Energy

• Thermal energy is the energy portion of a system that increases with its temperature. In a loose sense, "thermal energy" is a term used to describe the energy content of a system related to heating effects, e.g. temperature increase or decrease.

Mechanical Energy

• In physics, mechanical energy describes the potential energy and kinetic energy present in the components of a mechanical system (moving parts).

• E.X. a car has many different mechanical energy systems in it.

Electric

• The electric energy is the potential energy associated between charged particles (i.e. electrons) contained within a system.

Chemical• Chemical energy is the greatest source of

energy used by man. From flashlight batteries to commercial airlines, it is the energy released from chemical reactions. Paradoxically, most of the electricity produced in the world comes from the chemical energy released in the burning of coal, oil and gas.

Energy Transfer Example

Practice

Solar

Electric

Chemical

Electrical/Thermal

ChemicalChemical

Energy transfer all around us!

• Ecosystem level energy transfer

Powerful Classroom Assessment: Aquarium Systems

Attributes of a Description for Awarding Value Points

Performance Description Value Points

Typical Results

Light energy to chemical energy: Light energy is … 1 25%

Where transformation took place (in plants): …by the plants… 1 80%

Chemical energy to chemical energy: This chemical energy is transferred to insects… 1 41%

Where transformation took place (plants to insects): …as they (insects) eat the plants. 1 73%

Chemical energy to chemical energy: The chemical energy or food is then transferred to fish… 1 33%

Where transformation took place (insects to fish): …when fish eat the insects. 1 71%

Transfers/transformations are in the correct order 1 75%

Rubric for Write a Conclusion Items

Description of Attributes Value Pts

2006 Results

Conclusive Statement correctly answers the investigative question. As water temperature increased … 1 78%

Supporting data should at least be over the entire range of the conditions investigated. Thus the minimum reported data are lowest and highest conditions of the manipulated variable.

Supporting Data for 10° C: The lowest water temperature … 1 42%

Supporting Data for 30° C: The highest water temperature … 1 48%

Explanatory language is used to connect the supporting data to the conclusive statement.

So changing the water temperature by 20 degrees caused the …

1 46%

Write Conclusions to Investigations

A technique seen during scoring the 2006 G5 Science WASL

Question: What is the effect of X on Y?

PHLOWPrediction correct. High 11 Low only 3Wrap-up: This is my conclusion.

XY

T1 T2 T3 Avg.

Low 3 4 5 4

Med. 7 6 8 7

High 11 10 9 10

X vs. Y

Powerful Classroom Assessment: Aquarium SystemsItem 10: Plan an Investigation (continued)

Attributes of an Investigation

(see yellow rubric)Value Points

2005 Results

Prediction 1 61%

Prediction Reason

(Must be a cause-effect reason)1 11%

Materials 1 33%

Procedure:

Two controlled variables1 48%

One manipulated variable (with at least three conditions)

1 40%

One responding variable 1 52%

Powerful Classroom Assessment: Aquarium Systems

Item 10: Plan an Investigation (continued)

Attributes of an Investigation

(see yellow rubric)Value

Pts2005

ResultsProcedure (continued) :

Record measurements1 46%

Trials are repeated 1 14%

Experimental control condition 1 11%

Extra validity measure 1 5%

Logical steps 1 43%

Notes 1 through 3:

1. If the response does not plan an appropriate procedure… etc.