States of matter
What makes the particles in a solid different from those in a liquid or gas?
(Answer: They are packed tightly together and only vibrate in place.)
What kind of energy must be added or removed to change a substance’s state?
(Answer: Thermal energy)
What happens to particle motion when heat is added to matter?
The particles move faster and spread apart
What is a sign that a chemical reaction has occurred?
Color change, temperature change, bubbles, new substance, or light produced
What happens to the temperature of a substance while it is changing state?
It stays the same.
Which state of matter can flow but still keeps the same volume?
(Answer: Liquid)
When you put ice cubes in a drink and they melt, is energy being absorbed or released?
Absorbed
When heat is removed from a gas, what happens to the gas?
It condenses into a liquid.
What kind of reaction combines two or more substances into one new compound?
Synthesis
When frost appears on a car windshield, what change of state has occurred?
Deposition
Why do gases spread out to fill their entire container?
(Answer: Their particles move freely and are far apart.)
What happens to the speed of particles as a liquid freezes?
They slow down.
Why do liquids turn into gases faster on a hot day than on a cool day?
More thermal energy increases particle motion and causes faster evaporation
Which type of reaction breaks one compound into two or more simpler ones?
Decomposition
Give an example of a physical change that is not a chemical reaction.
Melting ice, cutting paper, breaking glass, etc.
Give one example of a crystalline solid and one example of an amorphous solid
(Answer: Crystalline—salt or sugar; Amorphous—wax or glass.)
Describe what happens during evaporation.
Particles at the surface of a liquid gain energy and become gas.
When matter changes from a liquid to a gas, what happens to the movement of the particles?
They move faster and spread farther apart as energy is absorbed.
What kind of reaction produces heat and light — like a burning candle?
Combustion / Exothermic
Which process forms new substances — physical or chemical changes?
Chemical changes.)
What do liquids and gases have in common?
Both take the shape of their container.
What phase change happens when water vapor turns into liquid droplets on a cold window?
Condensation
Compare the motion of particles in a solid, liquid, and gas.
Solids—vibrate in place; Liquids—slide past each other; Gases—move freely and quickly in all directions
What is the main difference between an endothermic and exothermic reaction?
Endothermic absorbs heat; exothermic releases heat.
Which change of state releases energy?
Condensation
During condensation, energy is released because gas particles lose heat as they slow down and move closer together.