Phase Change Basics
The process of a solid turning into a liquid is called ___.
Melting
Which physical property helps determine if a substance is solid, liquid, or gas at room temperature?
State of Matter
Heating ice causes it to change from ___ to ___.
Solid to Liquid
What happens to chocolate left in the sun?
Melts
If water stays at 0°C, what phase change is happening?
Melting/freezing
The change of a liquid to a gas below its boiling point is ___.
Evaporation
The temperature at which a solid turns into a liquid is called ___.
Melting Point
Why does water boil at a lower temperature on a mountain than at sea level?
Lower air pressure reduces the boiling point.
Dry ice turns from solid to gas. This is an example of ___.
Sublimination
A student observes bubbles forming at 100°C. What is happening?
Boiling (liquid to gas)
When a gas turns directly into a solid, this phase change is called ___.
Deposition
Why does sugar dissolve faster in hot water than cold water?
Heat increases the motion of particles, speeding up dissolution.
What happens to the temperature of a substance during a phase change?
It stays constant until the phase change is complete.
Why do puddles disappear on a hot day?
Water evaporates due to heat.
If a substance absorbs heat but doesn’t increase in temperature, what can be inferred?
A phase change is occurring.
The process of a liquid becoming a solid is ___.
Freezing
Density is a property of matter. How can it affect the behavior of a substance during phase changes?
Substances with different densities may float or sink, affecting heat transfer.
A metal rod is heated. Why does heat move from one end to the other?
Thermal energy transfers from warmer to cooler areas by conduction.
Why does sweating cool your body?
Evaporation of sweat removes heat from the skin.
A thermometer shows a substance changing from 50°C to 50°C while boiling. Explain.
Heat energy is used for phase change (liquid to gas), not increasing temperature.
The term for a substance changing from a solid directly to a gas without becoming liquid is ___.
Sublimation
Explain how the particle arrangement in solids, liquids, and gases affects phase changes.
Solids have tightly packed particles (hard to move), liquids have loosely packed particles (flow), gases have far apart particles (expand easily), affecting how they change states.
Explain why adding heat to a gas in a closed container increases pressure.
Heat increases particle movement, causing more collisions and higher pressure.
Icebergs float in water. How does this relate to the properties of matter during phase changes?
Ice is less dense than water, so it floats; density affects phase behavior.
Students measure ice melting at different rates in salt water vs. pure water. What does the data show?
Salt lowers the freezing point, so ice melts faster in salt water.