Classifying Changes in Matter
What are the three main states of matter?
Solid, liquid, and gas.
What is a physical change?
A change in appearance or state without changing chemical composition.
When a substance changes from a solid to a liquid or vice versa.
Phase change
What does the kinetic theory of matter state?
All matter is made of tiny particles that are in constant motion.
When ice melts in a drink, is it a physical or chemical change?
Physical change
What is the difference between a pure substance and a mixture?
A pure substance has only one type of particle; a mixture has more than one type.
What is a chemical change?
When a substance forms one or more new substances.
The temperature at which a substance changes from a solid to a liquid.
Melting point
Which state of matter has particles that move the least?
Solids
When a candle burns, what two kinds of changes are happening?
Both physical (wax melting) and chemical (combustion).
What kind of mixture has a uniform composition throughout?
A homogeneous mixture (solution).
Melting ice is what kind of change?
A physical change.
The temperature at which a substance goes from its liquid phase to its gas phase.
Boiling point.
Which state of matter has particles that move the fastest?
Gases
Why does frost form on a cold window?
Water vapor condenses and freezes (deposition).
What kind of mixture can you see different parts of?
A heterogeneous mixture.
Rusting iron is what kind of change?
A chemical change.
What is the phase change from liquid to gas called?
Evaporation or boiling.
What happens to particle motion when temperature increases?
Particles move faster.
Why does water boil faster at high altitudes?
Air pressure is lower, so it takes less energy for molecules to escape.
Is air a pure substance or a mixture?
A mixture (mostly nitrogen and oxygen gases).
Name two signs that a chemical change has occurred.
Color change, temperature change, gas or light produced, or a precipitate forms.
What is condensation?
The phase change from gas to liquid.
Why does a gas fill its container while a solid does not?
Gas particles move freely and spread out; solid particles are tightly packed.
What phase change happens when dry ice “smokes”?
Sublimation — solid carbon dioxide turning directly into gas.