Ch 10 Lesson 1: Changes of State

What is the process called when a liquid loses heat and becomes a solid?

freezing

What is the temperature where a solid turns into a liquid called?

melting point

What is the temperature where a liquid turns into a gas called?

boiling point

What is sublimation?

a change from solid straight to gas with no liquid step

What is a common substance that sublimates at room temperature?

dry ice

How can snow disappear without leaving a puddle?

it can sublimate from solid ice to water vapor

How can frost build up inside a freezer?

water vapor turns into ice on the cold freezer walls

In most materials how does the density of a solid compare to its liquid?

a solid is usually denser than the same material as a liquid

How does the density of ice compare to liquid water?

ice is less dense than liquid water

What do water molecules do just before freezing that makes ice less dense?

they spread out into an open crystal pattern

Why does temperature stay the same while a substance melts or boils?

the added energy breaks attractions between particles instead of raising temperature

What do the flat parts of a heating curve show?

a state change happening at constant temperature

For water, which needs more heat: melting or boiling?

boiling needs more energy than melting for water

Do melting and boiling points depend on how much of a substance you have?

melting and boiling points stay the same no matter how much you have

What is the melting point of water in degrees Celsius?

0 degrees Celsius

What is the boiling point of water in degrees Celsius?

100 degrees Celsius

What is evaporation?

liquid particles escaping into gas below the boiling point

How does evaporation change the temperature of a liquid?

it cools the remaining liquid

Why does sweating help cool your body?

evaporating sweat removes heat from your skin

Why can steam feel very hot when it touches your skin?

condensing steam gives off heat to your skin

What is condensation?

a gas changing into a liquid

What is thermal expansion?

matter getting bigger as it warms because particles push apart

What is thermal contraction?

matter getting smaller as it cools because particles pull closer

Which state of matter expands and contracts the most?

gas

Which state of matter expands the least when heated?

solid

How do liquids compare to solids and gases in thermal expansion?

liquids expand more than solids but less than gases

Why do bridges and sidewalks have expansion joints?

to leave room so they do not buckle when temperatures change

How can an alcohol thermometer measure temperature?

the liquid inside expands and rises when warmed

What might happen if a sidewalk had no gaps between sections?

it could crack or bulge on hot days

What happens to particle motion when an object loses heat?

particles move slower and have less kinetic energy