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

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Presentation on theme: "Notes – Changes in States of Matter Chapter 6, Lesson 2."— Presentation transcript:

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

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

3 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.

4 Temperature, Thermal Energy, & Heat

5 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

6 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.

7 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.

8 Temperature, Thermal Energy, & Heat

9 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.

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

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

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

13 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.

14 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.

15 Melting

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

17 Freezing

18 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.

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

20 Vaporization: Boiling

21 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.

22 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.

23 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

24 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.

25 Condensation

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

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

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

29 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.

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

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

32 Changes in Energy Among States of Matter

33 1. The point at which a liquid changes to a gas is called ____. Amelting point Bfreezing point Ccondensation point Dboiling point 6.2 Changes in States of Matter

34 2. A liquid can change to a gas through ____. Aevaporation Bfreezing Cmelting Dsublimation 6.2 Changes in States of Matter

35 3. Thermal energy must be ____ when a liquid changes to a ____. Alost; gas Bgained; solid Clost; solid Dincreased; solid 6.2 Changes in States of Matter

36 4. Sublimation occurs when a solid changes into a ____. Aliquid Bgas Cplasma Dsteam

37 5. As air pressure ____, the ____ of a liquid increases. Adecreases; boiling point Bdecreases; freezing point Cincreases; freezing point Dincreases; boiling point

38 6. Adding thermal energy can ____ or ____. Alower temperature; change the state of matter Bincrease temperature; lower temperature Cincrease temperature; change the state of matter Dremove kinetic energy; change the state of matter SCI 3.e

39 7. One glass of water has a temperature of 30°C and another glass of water a temperature of 40°C. Which is true? AThe glass of water at 30°C has lower average kinetic energy. BThe glass of water at 40°C has lower average kinetic energy. CThe two glasses have equal average kinetic energy. Dnone of the above SCI 3.e


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