Year 9 Science · Unit 3 · Lesson 2
Foundation Worksheet
Learning Goals
Fill the gap
Choose the correct word from the word bank to complete each sentence. Two words will not be used.
The law of of energy states that energy cannot be or destroyed. A group of objects being studied together is called a . In a system, energy cannot enter or leave, so the total energy remains constant. When energy seems to disappear, it has actually been transferred to the surroundings as . Scientists say energy always for, meaning every joule can be traced. Energy that does not do the useful job is called energy.
True or False? Fix the false ones
Circle T or F for each statement. If the statement is false, rewrite it correctly on the line below.
A closed system can create energy if enough force is applied.
Correct it:
Energy that is "lost" to heat is transformed into thermal energy that spreads into the surroundings, it still exists.
Correct it:
Conservation of energy means that nothing in the universe ever moves or changes.
Correct it:
An open system allows energy to enter and leave, so its total energy can change.
Correct it:
No real machine can be 100% efficient because some energy will always become waste thermal energy.
Correct it:
1. When a bouncing ball eventually stops bouncing, where has its energy gone? Explain using the law of conservation of energy.
2. A car engine receives 100 J of chemical energy from petrol and converts 20 J into useful kinetic energy. How much energy becomes waste? Where does this waste energy go?
Wrap Up
In one sentence, what was the main idea of this lesson?