Notes – Changes in States of Matter Chapter 6, Lesson 2

Temperature, Thermal Energy, & Heat Changes in energy can cause matter to change from one state to another. A state change happens because of the change in motion of particles in an object. Matter Changing State

Temperature, Thermal Energy, & Heat Even when an object is not moving, the particles in the object are moving. The particles have kinetic energy, which is energy of moving things. The gas particles inside the balloon have energy because they are moving.

Temperature, Thermal Energy, & Heat

Temperature, Thermal Energy, & Heat Temperature is a measure of the average kinetic energy of the particles in a material. Particles in matter move faster as the temperature increases. lower temperature higher temperature

Temperature, Thermal Energy, & Heat A thermometer is used to measure temperature. Particles in the thermometer’s gauge increase their speed when heated and start moving farther apart, causing the liquid in the thermometer to rise.

Temperature, Thermal Energy, & Heat Particles in a substance have potential energy. Potential energy decreases as particles move closer together. Potential energy increases as particles move farther apart.

Temperature, Thermal Energy, & Heat

Temperature, Thermal Energy, & Heat The total energy of the particles of a substance is its thermal energy. Includes kinetic energy and potential energy of a substance’s particles A substance’s liquid state has more thermal energy than its solid state A substance’s gas state has more thermal energy than its liquid or solid state.

Temperature, Thermal Energy, & Heat Heating adds thermal energy. Cooling removes thermal energy.

Temperature, Thermal Energy, & Heat When kinetic energy increases, the temperature of a substance increases. When potential energy increases, the substance changes state.

Melting solid → liquid Thermal energy is absorbed. Potential energy increases. Melting point is the temperature at which a material changes from solid to liquid.

Melting Thermal energy is added to a solid, & the temperature increases until the melting point is reached. The substance will not increase temperature until it has completely melted.

Melting The average kinetic energy does not change, only the potential energy changes. The attractive forces become weaker as particles increase speed and move farther apart.

Melting

Freezing liquid → solid Thermal energy is released. Potential energy decreases. Freezing point is the temperature at which a liquid changes to a solid.

Freezing

Vaporization liquid → gas Thermal energy is absorbed. Particles become too spread out and the attractive forces are too weak to keep the particles close together. Vaporization can occur both at the surface and inside the liquid.

Vaporization: Boiling Vaporization that occurs inside the liquid. Boiling point refers to the temperature that boiling occurs in a substance.

Vaporization: Boiling

Vaporization: Boiling The boiling point depends on the pressure exerted on the liquid. Bubbles in the liquid must form for boiling to occur. As air pressure increases, it becomes harder for the bubbles to form. The boiling point increases as air pressure increases.

Vaporization: Evaporation Evaporation is vaporization that occurs at the surface of a liquid. Evaporation occurs both at the boiling point and temperatures below the boiling point.

Vaporization: Evaporation The liquid gains thermal energy, and molecules on the surface gradually escape into the atmosphere (i.e.) water cycle, a puddle after rain, sweating to cool you down

Condensation gas → liquid Thermal energy is released. The gas particles slow down and move closer together until the attractive forces hold them together and a liquid forms.

Condensation

Sublimation solid → gas Thermal energy is absorbed. Bypasses liquid state completely. Dry ice (solid carbon dioxide) changes from a solid to a gas.

Deposition gas → solid Thermal energy is released. Bypasses liquid state completely. Water vapor changes directly to ice as frost on leaves.

Adding Thermal Energy The temperature of ice increases until the melting point is reached. The temperature stays constant as the ice melts.

Adding Thermal Energy After the ice has melted, the temperature increases until the boiling point is reached. The temperature stops increasing until all the water has changed to water vapor.

Adding Thermal Energy Adding more thermal energy causes the temperature of the water vapor to increase.

Removing Thermal Energy Water vapor changes back into ice by removing thermal energy.

Changes in Energy Among States of Matter

1. The point at which a liquid changes to a gas is called ____. 6.2 Changes in States of Matter 1. The point at which a liquid changes to a gas is called ____. A melting point B freezing point C condensation point D boiling point

2. A liquid can change to a gas through ____. A evaporation B freezing 6.2 Changes in States of Matter 2. A liquid can change to a gas through ____. A evaporation B freezing C melting D sublimation

3. Thermal energy must be ____ when a liquid changes to a ____. 6.2 Changes in States of Matter 3. Thermal energy must be ____ when a liquid changes to a ____. A lost; gas B gained; solid C lost; solid D increased; solid

4. Sublimation occurs when a solid changes into a ____. A liquid B gas C plasma D steam

5. As air pressure ____, the ____ of a liquid increases. A decreases; boiling point B decreases; freezing point C increases; freezing point D increases; boiling point

6. Adding thermal energy can ____ or ____. SCI 3.e 6. Adding thermal energy can ____ or ____. A lower temperature; change the state of matter B increase temperature; lower temperature C increase temperature; change the state of matter D remove kinetic energy; change the state of matter

A The glass of water at 30°C has lower average kinetic energy. SCI 3.e 7. One glass of water has a temperature of 30°C and another glass of water a temperature of 40°C. Which is true? A The glass of water at 30°C has lower average kinetic energy. B The glass of water at 40°C has lower average kinetic energy. C The two glasses have equal average kinetic energy. D none of the above