Electric charge is a physical property. It occurs between particles or objects. It causes them to attract or repel each other. They do not even have to touch. This is unlike the typical push or pull you may be familiar with. All electric charge is based on the protons and electrons in atoms. A proton has a positive electric charge. An electron has a negative electric charge. Forces on Charged Objects Most atoms are balanced electrically. They have the same number of positive and negative charges. Therefore, the number of protons equals the number of electrons. Neutrons do not matter as they have no charge. When an object loses some electrons, it becomes positively charged. There are now more protons than electrons inside the atom. The lost electrons may remain free. Or, they may attach to another object. The new object now has more electrons than protons. It then becomes negatively charged.

Question: "If a particle loses some of its protons, what is the particle's charge?"

Answer: "Lost protons will attach to another particle"

Response: no

Fossils can be used to match up rock layers. As organisms change over time, they look different. Older fossils will look different than younger fossils. Some organisms only survived for a short time before going extinct. Knowing what organisms looked like at certain times also helps date rock layers. Some fossils are better than others for this use. The fossils that are very distinct at certain times of Earths history are called index fossils. Index fossils are commonly used to match rock layers. You can see how this works in Figure 2.30. If two rock layers have the same index fossils, then they're probably about the same age.

Question: "How are index fossils useful?"

Answer: "For fuel"

Response: no

Surely, you have noticed the tall poles along the roadside. Do you know what is on top of those poles? Thats right, wires that carry electric current. These wires carry electric current to your home. But what is electric current? Electric current is actually the flow of electrons. You may recall, an electron is the outer-most particle in an atom. They have a negative charge. Electricity is the continuous flow of these particles. Electrons are able to move through wires. Their speed can even be measured. The SI unit for electric current (or speed) is the ampere (A). Ampere is often shortened to amp. Electric current may flow in just one direction, or it may keep reversing direction. Direct current (DC) flows in only one direction. Direct current is what is used in devices like flashlights. Alternating current (AC) flows in two directions. This is the type of current that flows into your home through wires.

Question: "What is on top of the poles on the roadside?"

Answer: "Pipes"

Response: no

Joe's parents are farmers and they have a huge farm with cows, chickens, and ducks. Joe loves the farm and all the things he gets to play around and play on. One day, Joe's father told him not to get near a tractor that was sitting in the field. His father was worried that Joe would climb on it and hurt himself. Joe went out to the field and was feeding the horses and cows. When he was done, he saw the tractor his father told him not to get near. He knew that climbing on the tractor wouldn't hurt anything, so he did. He climbed on to the seat and sat there. Then, he pretended he was his father and pretended that he was driving the tractor. Joe's father saw him playing on the tractor and called for him. Joe heard his father calling for him and got off the tractor really fast. When he did that, he fell off and hurt his arm. Joe was in pain and his father came running to check on him and picked him up and sat him on a bench and asked him why he did that. Joe looked at his father and said, "I wanted to be like you." Joe's father gave him a hug and asked him if he wanted to ride with him on the tractor. Joe did and after he got a bandage on his arm, he and his father rode in the field on the tractor.

Question: "What had he just finished doing when he saw the tractor"

Answer: "Feeding the chickens and ducks"

Response:
no