This is called Quartzite. It was once sandstone, but heat and pressure changed it by fusing the grains of sand to each other, making it much harder. What kind of rock is it?.

1. Igneous

   No. Igneous rocks formed from magma or lava. That would have melted the sand grains. This is not an igneous rock.

2. Sedimentary

   No. Sedimentary rocks are deposited by wind, water, ice, or gravity, and they often contain fossils. When it was sandstone it was a sedimentary rock.

3. Metamorphic

   Yes!. This quartzite been changed by heat and pressure from a different kind of rock. It is metamorphic.

4. Quartzite is not a rock.

   No. Quartzite is a naturally occurring solid that forms large layers in the Earth. Quartzite is a rock.

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Incandescent light bulbs use electrical energy to produce light energy, but it is not a direct transformation. Instead, the electrical energy is changed to a different form of energy, and then to light.

What form of energy does the "?" represent?

1. Sound

   No. Electrical energy can be transformed into sound energy, but that would not cause the bulb to light.

2. Thermal

   Yes. As electrical energy flows through the filament, resistance changes the electrical energy into thermal energy. When the filament gets hot enough, some of the thermal energy is converted into light.

3. Radiation

   No. The electrical energy is not transformed into radiation.

4. Friction

   No. The electrical energy is not transformed into friction.

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