When a physical change occurs, the mass of the substance is conserved. this means that the total mass of the substance remains the same from beginning to end. the physical properties of the substance, such as size and shape, may change, but the amount of matter in the substance does not change.

Solar cell a produces 100 joules of energy, when a light source is shown on it for 3 minutes. solar cell b produces 200 joules of energy when the same light source is shown on it for 5 minutes. which solar cell works better? a) solar cell b, because it produces more energy. b) solar cell b, because it generates more power. c) solar cell a, because it produces energy quicker. d) solar cell a, because it generates a greater wattage. eliminate

The star betelgeuse is about 600 light-years away. if it explodes tonight, a. we'll know because debris from the explosion will rain down on us from space.b. we'll know it immediately because it will be brighter than the full moon in the sky.c. we won't know about it until 600 years from now.d. none of the above.

For waves in the ocean, the medium of the waves is a. air b. water c. energy d. a passing boat