science: study physical and chemical changes

Question Answer
Definition of physical change altars a substance but does not change it into another substance. ex: paper when you tear it
Definition of chemical change it is changed into another substance with different properties. ex: burning wood
Definition of thermal energy The total energy of a substances particles due to their movement or vibration
Definition of chemical energy The energy stored within chemical bonds within matter
Whats true about changes in matter? Matter changes whenever energy is added or taken away
What is the principle that says in every physical or chemical change the total amount of energy stays the same? Law of Conservation of Energy
The change in state from solid to a liquid is called melting
in most pure substances, melting occurs at a temperaturethat is specific to the substance, called the melting point
the change in state from a liquid to a solid is called freezing
T or F? When the temperature of water drops to 0 degrees C, its molecules form regular patterns, which are crystals True
the change in state from the liquid to the gas state of matter is called Vaporization
Vaporization includes… evaporation whic occurs on the surface of the liquid; and boiling which occurs throughout the liquid
each liquid boils only at a certain temperature, which is called boiling point
Why is the boiling point of water lower in the mountains than it is at sea level? In the mountains, air pressure is lower, and so is the boiling point
The change in state from a gas to a liquid is called condensation
T or F? Condensation is the opposite of vaporization. True
When condensation occurs, does gas lose or gain thermal energy? loses thermal energy
Example of vaporization liquid water changes into vapor
Example of evaporation a puddle dries up after a rain shower
Example of boiling a pot of water on a stove reaches its boiling point
Example of condensation clouds form from water vapor in the sky
The change in state from a solid directly to a gas without passing through the liquid state is called sublimation
T or F? Changes in state are example of chemical changes. False; physical
Whats true about chemical reactions? -all chemical reactions either absorb or release energy
-in some chemical reactions, two or more substances combine, forming one or more new substances
-all chemical reactions form new substances

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