Energy often changes from one form to another. For example, the drummer transfers motion to sound energy. When the moving drumstick strikes the drum head, the drum starts to vibrate. The motion of the vibrating drum head creates the sound you hear. Any form of energy can change into any other form. Frequently, one form of energy changes into two or more different forms. Have you ever sat in front of a campfire? What are two things you notice? The fire creates light. It is also warm by the fire, meaning it creates heat. The energy of the fire comes from the stored energy in the wood. The wood contains chemical energy. As it burns, the chemical energy is changed into light and heat. Not all chemical energy changes produce light and heat. Our cars use gasoline as a fuel. Gasoline contains chemical energy. When our cars burn gasoline in their engines, it is converted into motion and heat. When energy changes forms, energy is conserved.

Question: "The motion of a vibrating drum head creates what?"

Response: "Sound"

A: yes

Static electricity is like a teeter-totter. What happens if a teeter-totter is balanced? Correct! It does not move. What about when its not balanced? Yes, it will now begin to move. Charges move when they are not balanced. Charges can build up by friction. Maybe you rub your feet on a wool mat or carpet. Rubber soled shoes readily gain charges. The wool carpet easily gives up charges. The two items become unbalanced. One item has a positive charge. The other has a negative charge. The difference in charge is called static electricity. Just like the teeter-totter, something is going to move. Positive charges build up on the mat. Negative charges build up on you.

Question: "What happens if a teeter-totter is balanced?"

Response: "It means the charges are imbalanced"

A: no

(CNN) -- English club Chelsea have completed the signing of Oriol Romeu from Spanish and European champions Barcelona. The 19-year-old is currently playing for Spain at the World Under-20 Championships in Colombia and has signed a four-year deal with last season's Premier League runners-up. The deal is worth $7 million and includes a buy back clause, set at $14 million after the first year and $21 million after the second. Romeu started his career at Barcelona's city rivals Espanyol before joining the Camp Nou academy in 2004. The midfielder, who can also play in central defence, made his debut for Barcelona in last season's Spanish Supercup match with Seville and got his first taste of league action against Deportivo in May 2010. He has played 90 minutes in both of Spain's games at the World Under-20 Championships, when they beat Costa Rica and Ecuador. Chelsea official web site confirmed the signing and said Romeu is "renowned for his strength and his expansive passing ability." Another player leaving Barcelona is Jeffren Suarez after he agreed to join Sporting Lisbon. The Portuguese outfit have paid $5 million for the 23-year-old which, like the Romeu deal, includes a buy back option. Jeffren joined Barca from Tenerife in 2004 and made his debut for the Catalan club in the 2006-07 season.

Question: "How old is Oriol Romeu?"

Response: "Twenty-one"

A:
no