Which organelle makes the cell's energy?
You said the nucleus makes the cell's energy. The instructions live in the nucleus, but the energy-making has a different address.
Try this lessonExplore how the world works.
Explore living things, forces, energy, and more with short practice questions and helpful clues.
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Ask about your own questionLife science 7
Which way does water move through a cell membrane?
You said water rushes into the cell because the cell needs it. Water does not choose sides; it simply spreads toward the saltier solution.
Try this lessonWhere does a growing plant's mass come from?
You said the soil feeds the plant. Soil holds water and minerals, but most of the tree's wood is built from carbon in the air.
Try this lessonIs breathing the same as cellular respiration?
You said respiration happens in the lungs. The lungs move air in and out; the useful energy release happens inside every one of your cells.
Try this lessonWhat happens to the DNA when a cell divides?
You said the DNA splits in half so two cells can share it. The DNA is copied first, and both new cells end up with a complete set.
Try this lessonCan a parent's workout be passed to their children?
You said the champion's kid will be strong. Inheritance repeats instructions, not workouts: training changes the body, not the genetic code.
Try this lessonWhy does a Punnett square have four boxes?
You said each parent donates both of its alleles. The two alleles separate, and each parent passes on just one for the trait.
Try this lessonEcology 2
Which way do food web arrows point?
You said the arrow should point from the eater to the food. It is the opposite: the arrow starts at the food and points to the eater.
Try this lessonWhy are there so few wolves and so many plants?
You said the top of the pyramid holds the most energy because it holds the biggest animals. The pyramid is wide at the bottom, and each level up holds roughly a tenth as much energy.
Try this lessonEarth & space 8
Where does rain come from, and where do puddles go?
You said clouds are water vapor. Vapor is an invisible gas; clouds are made of tiny liquid droplets that vapor turned into.
Try this lessonIs carbon ever created or destroyed?
You said burning makes new carbon. The atoms were already here; burning just moves stored carbon back into the air.
Try this lessonCan one kind of rock become another?
You said granite stays granite forever. Given enough time, granite can become sediment, or metamorphic rock, or magma, and back again.
Try this lessonWhy do the continents drift?
You said the continents drift because Earth is cracking as it cools. The plates ride slow currents of heated rock in the mantle.
Try this lessonWhat happens when cold air meets warm air?
You said a front is a wall of dark cloud. A front is the moving boundary between two air masses; clouds and storms gather along it.
Try this lessonWhy does the Moon change shape?
You said Earth's shadow covers the Moon to make phases. A phase is only how much of the Moon's sunlit half is facing us.
Try this lessonWhy is it hot in summer and cold in winter?
You said summer comes when Earth is near the Sun. Earth is closest to the Sun in early January, during northern winter. The tilt is the cause.
Try this lessonWhy doesn't the Moon fall down to Earth?
You said there is no gravity in space, so astronauts float. The space station is falling around Earth the whole time.
Try this lessonPhysical science 7
Why does your head jerk forward when the bus stops?
You said a moving ball slows down in space without a push. Nothing pushes or pulls it there, so Newton's first law says it keeps going.
Try this lessonWhat is the net force when pulls go against each other?
You said a 100 N pull right and a 40 N pull left give 140 N. They fight: the net force is the difference, 60 N, and it points the stronger way.
Try this lessonIs acceleration just going fast?
You said a car cruising at 55 mph has lots of acceleration because it is fast. Constant speed on a straight road is zero acceleration.
Try this lessonDoes a parked coaster car at the top of a hill have kinetic energy?
You said the coaster car at the top has kinetic energy because it is about to move. Stored height energy is potential; motion energy comes after the drop.
Try this lessonWhat really travels along an ocean wave?
You said the water rides along with the wave to the beach. Watch a cork bob: it stays, and only the energy travels.
Try this lessonDo molecules in a solid ever move?
You said the molecules in a solid are frozen still. They are never still: every particle vibrates, and heat changes how fast they shake.
Try this lessonDoes heavy mean it sinks?
You said the steel ship is too heavy to ever float. The ship's average density, steel plus the air inside it, is less than water, so it floats.
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