Forces and Motion
What force pulls objects toward Earth?
gravity
What are the three common states of matter?
Solid, liquid, and gas
What is the smallest basic unit of a living organism?
A cell
What star is at the center of our solar system?
The Sun
What form of energy allows us to see objects?
Light energy
What force can slow down a moving object when two surfaces rub together?
friction
What happens to the particles of a substance when it is heated?
They generally move faster.
What process do plants use to make sugars using light energy?
Photosynthesis
What causes day and night on Earth?
Earth's rotation on its axis
A book is sitting on a high shelf. What type of stored energy does it have because of its position?
Gravitational potential energy
A soccer ball is sitting still. What must happen for it to begin moving?
A force, such as a push or kick, must act on it.
Is melting ice a physical or chemical change?
Physical change
In a food chain, what is an organism that makes its own food called?
A producer
About how long does Earth take to orbit the Sun once?
One year, or about 365ΒΌ days
What type of energy does a moving object have?
Kinetic energy
Two students push a box in opposite directions with equal force. What happens to the box?
The forces are balanced, so the box does not accelerate.
A student mixes salt into water until the salt seems to disappear. What happened to the salt?
It dissolved and is still present in the solution.
What important role do decomposers play in an ecosystem?
They break down dead organisms and recycle nutrients.
Why does the Moon appear to change shape during the month?
We see different portions of its sunlit half as the Moon orbits Earth.
A lamp changes electrical energy mainly into what two forms of energy?
Light and thermal (heat) energy
A skateboarder pushes backward against the ground. Why does the skateboarder move forward?
The ground pushes the skateboarder forward with an opposite force.
Burning wood creates ash, gases, and other substances. Why is this considered a chemical change?
New substances with different properties are produced.
The rabbit population in an ecosystem suddenly decreases. What could happen to predators that depend on rabbits for food?
Their populations may decrease or they may need to find other food sources
Why does Earth experience seasons?
Earth's axis is tilted as Earth orbits the Sun, changing the angle and duration of sunlight received by each hemisphere.
A roller coaster starts at the top of a hill and travels downward. Describe the main energy transformation.
Gravitational potential energy changes into kinetic energy.