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Typical Solid
Typical Liquid
Typical Gas
States of Matter
States of Matter
We will consider 4 states of matter: Solid, Liquid, Gas, and Plasma.
All changes in state are physical changes. The matter is not chemically altered.
Temperature!
Temperature!
Temperature is a measure of the average kinetic energy of the molecules.
In other words, Temperature measures the bounciness of matter.
Cold
Cold
If something is cold, the atoms are quiet and sleepy.
Warm
Warm
Warmer atoms masses bounce more.
Hot
Hot
Hot atoms bounce the most.
In science, we will use the Celsius scale.
Ice
Ice
Water is one of the few compounds that become less dense when it freezes.
As the water molecules slow down, hydrogen bonds help the molecules to form crystalline structures.
The ice takes up more volume, the density decreases, and the ice floats in water.
Ice = Solid
Ice = Solid
Melting Ice
Melting Ice
Ice is the solid form of water.
Water freezes and melts at 0 degrees Celsius. The hydrogen bonds between water molecules cause the ice to take up more space, hence decreasing its density. Ice floats in water because its density is less than 1 gram per cubic centimeter.
Heating Liquid Water
Heating Liquid Water
At zero degrees Celsius, ice and water can coexist. As heat is added, the water molecules vibrate apart and the solid ice turns to the liquid form of water.
The temperature of liquid water can only increase once all ice has melted. The kinetic energy and temperature of the water both increase as heat is added. In fact, the temperature is a measure of the average kinetic energy of the molecules. Temperature measures the bounciness of matter.
Water = Liquid
Water = Liquid
Turning Water into a Gas
Turning Water into a Gas
As the heat continues to enter the water, some water molecules have enough kinetic energy and leave as a gas. The water molecules vaporize.
We can see steam but is impossible to see water vapor. Under normal conditions, water boils (and condenses) at 100 degrees Celsius.
One cannot increase the temperature of boiling water beyond 100 degrees under normal conditions. Steam, however, can be superheated well beyond 100 degrees Celsius.
Water Vapor = Gas
Water Vapor = Gas
These bubbles are water vapor.
Boiling is a form of vaporization.
Consider water. When heat is added to water, the molecules vibrate with so much energy that they turn from liquid to gas. The bubbles are water vapor! Boiling is when phase change happens within the water.
Phase change also occurs at the surface of water. This is a physical change. The formula for water is not changed.
Plasma is a form of matter that consists of free electrons and ions that are independent of the nuclei of atoms. Plasma examples include the sun, fluorescent lights, fire and lightning.
Lightning is Plasma
Pressure is Proportional to Temperature
Pressure is Proportional to Temperature
Cotton lights on fire when it is compressed in this device. This happens because increasing the pressure also increases the temperature.
The opposite is also true. A decrease in pressure will cause the temperature to drop.
You can experience this phenomenon if you spray on sunblock. The contents of the can are pressurized. Once you spray the chemicals on you, it feels cold because the pressure has been lowered.
Condensation
Condensation
The change of state from a gas to a liquid is called condensation.
You can see condenstation on cold windows and mirrors in your home.
Water Cycle
Water Cycle
Water evaporates from water and enters the air as water vapor.
Water vapor condenses at high altitudes and forms clouds.
Phase Changes -Water
Phase Changes -Water
Water is an incredible substance because it can change between three states: solid (ice), liquid (water), and gas (water vapor).
These changes are called phase changes, and they happen when water either gains or loses energy.
The three main phase changes for water are melting, freezing, and evaporation.
When ice melts, it changes from a solid to a liquid. This happens when the temperature rises to 32°F (0°C), the melting point of water. The heat energy causes the molecules in the ice to move faster and break free from their solid structure. This is why ice cubes turn into water when left out at room temperature.
Freezing is the opposite of melting. When liquid water loses heat and its temperature drops to 32°F (0°C) or lower, it turns into ice. The molecules in the water slow down and lock into a solid structure. This is why puddles freeze into ice in the winter when it’s cold.
Evaporation happens when liquid water turns into a gas called water vapor. This process occurs when water is heated, like when the sun warms a puddle, or when you boil water. The heat energy makes the water molecules move faster until they escape into the air.
The opposite of evaporation is condensation, which happens when water vapor cools and turns back into liquid, like the droplets on a cold glass of water on a hot day.
These phase changes are part of the water cycle, which helps move water around our planet. The ability of water to change states is essential for life on Earth!
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