Changes of State

1. Matter mostlyexists is one of three states or phases: solid, liquid or gas. An increase or decrease in energy (temperature) can lead to a change of phase. Changes of State Sublimation (Deposition): Change from gas directly to a solid or from a solid directly to a gas.

2. Types of Changes of State Solidification/Crystallization (freezing): Change from liquid to solid. Condensation: Change from gas to liquid. GAS SOLID LIQUID Vaporization/Evaporation: Change from liquid to gas. Melting: Change from solid to liquid.

3. Stored Heat and Changes of State When an objectis in one of the three states, its temperature rises as thermal energy is added to it. When an objectis in one of the three states, its temperature rises as thermal energy is added to it. Temperature rises Temperature rises LIQUID BASALT SOLID BASALT Melting/Solidification If an object is in the process of changing its state of matter, the temperature remains the same as thermal energy is added to it. THERMAL ENERGY THERMAL ENERGY

4. Stored Heat and Changes of State Melting/Solidification SOLID BASALT LIQUID BASALT THERMAL ENERGY THERMAL ENERGY When an object is changing phase, the thermal energy added to it does not increase the temperature of the object. The added thermal energy becomes a form of stored or potential energy. This is also known as latent heat. In order for an object to change phase from: solid  liquid  gas The object GAINS stored HEAT ENERGY In order for an object to change phase from: gas liquidsolid The object MUST RELEASE its stored HEAT ENERGY What happens to the thermal energy of the solid basalt when it melts? When the basalt melts the thermal energy will not raise the temperature of the rock. Instead the rock will gain stored heat energy.

5. Stored Heat and Changes of State of Water Gain Heat Energy Lose Heat Energy How long did it take for the water sample to boil? 4 minutes. How long was the change of state for the water sample from liquid to gas (vapor)? 4 minutes What happens to the heat energy added to the water sample after 4 minutes into the experiment? The added heat energy did not change the temperature of the water. Heat energy was absorbed and stored as the water changed state from liquid to gas.

6. Stored Heat and Changes of State of Water Heat gained during vaporization: 2260 J/g Heat gained during melting: 334 J/g Heat released during condensation: 2260 J/g Heat released during freezing: 334 J/g RT = Pg. 1

7. Earth’s Energy Supply: Solar Energy The majority of Earth’s energy comes from the Sun. The sun “radiates” all forms of electromagnetic energy including visible light (greatest intensity). Solar energy is a product of nuclear fusion. In nuclear fusion, two light elements (hydrogen) are combined to form one heavier element (helium) under tremendous amounts of heat and pressure. The process of nuclear fusion produces a great amount of energy – including the electromagnetic energy that is radiated to Earth. NOTE** Deuterium and Tritium are two forms of hydrogen.

8. Earth’s Energy Supply: Earth’s Interior Some of Earth’s energy comes from the planet itself. Heat from the Earth can be changed to kinetic energy as mountains are made and volcanoes erupt. The Earth still is generating heat from its own creation some 4.5 billion years ago (Earth’s core). The core is the source of gravity for the planet. Materials being pulled towards the center of the Earth generate energy. Most energy created in Earth’s interior is from nuclear decay or nuclear fission. Nuclear fission is the opposite of nuclear fusion. In nuclear fission a heavier, unstable element (uranium) “decays” or is broken down into two lighter elements (rubidium and cesium). This process releases a large amount of energy. Today’s nuclear reactors use this same process as an alternative energy source to the burning of fossil fuels.