Science Definitions

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  • Distance is how far one thing is from another thing.
  • It can be measured as lines or circles, or up or down.
  • Someone who goes around in a circle has traveled a distance, even though his position has not changed



  • Whenever there is an interaction between two objects, there is a force upon each of the objects.
  • They could pull on one another (The sun pulls on earth. Earth pulls on the moon), or push on one another (mug on a counter – the mug pushes on the countertop and the countertop pushes in the opposite direction). When the interaction stops, the two objects no longer experience the force.
  • Forces only exist as a result of an interaction.



  • Convection is how hot air rises above and cool air replaces it.
  • It also happens in the ocean when hot water rises above cold water.
  • Convection causes the weather, like wind or rain or storms.


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  • Cohesion is when two alike molecules stick together.
  • Water molecules stick together (a pin can float on the surface of water), move together (on a rope), and pile upon one another (on a coin).


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  • Energy is the ability to do work.
  • Energy is never really destroyed. It is just transferred from one form to another, doing work in the process.
  • Energy could take the form of movement (kinetic energy).
  • Chemical (like digesting food and turning it into power to help us breathe, move, and think).
  • Energy could take the form of heat (Thermal energy).
  • The sun gives us light and heat (Light energy and Thermal energy).
  • When air moves through an object it vibrates (Sound energy).


  • Gravity is a force of attraction that pulls together all matter (anything you can physically touch).
  • The more matter something has, the greater the force of its gravity. (more matter means more atoms and more atoms mean more mass).
  • That means really big objects like planets and stars have a stronger gravitational pull.


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  • A lodestone is a naturally magnetized piece of the mineral magnetite.
  • They are naturally occurring magnets, which can attract iron.
  • A magnet is a metal which attracts or repels other materials.
  • A magnet is made from magnetic materials such as iron, nickel, steel or cobalt.


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  • Friction is a force, the resistance of motion when one object rubs against another.
  • Whenever two objects rub against each other, they cause friction.
  • Friction causes an object’s movement to be slower.


  • A sound is anything that can be heard. Music, the barking of a dog, and the voice of a friend are all sounds.
  • Sound is created by the vibration of atoms (when atoms vibrate they move back and forth or up and down).
  • Sound travels in waves and can move through solids (wood), liquids (water), or gases (air).
  • Atoms in solids are so close together (very dense) – sound moves from one atom to the other very fast.
  • Atoms in liquids are less dense than solids – sound travels slower in liquids than in solids.
  • Atoms in gases and so random and crazy – sound gets lost in open spaces.
  • There is no air in space and this is why there is no sound in space, since sound needs air.

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