Chapter 4 States of Matter

1. Chapter 4States of Matter Section 4-1 Solids

2. Quiz next class on Sec. 4-1

3. Everyday, water changes from a solid to a liquid to a gas and back again How can we explain this?

4. Let’s do a quick review of what you already know: • Matter has three states: • Solid • Liquid • Gas Matter is anything that takes up space and has mass.

5. More review • Most matter is made up atoms and molecules. • An atom is the smallest particle that makes up a given element of matter. • When two or more atoms combine, they make a particle called a molecule.

6. O H C O H H H C H Liquid Glucose Blood sugar O Solid O C H H O C H Water H C H O H Gas C N N H H O Nitrogen H Examples of molecules

7. ??? • Why is water a liquid, nitrogen a gas and glucose a solid? • What makes a solid a solid? a liquid a liquid? a gas a gas?

8. One clue to this mystery was first reported in 1827 by scientist Robert Brown – • Brownian Motion

9. Under a microscope, dust particles can be seen to move in a random, jerky way.

10. The water molecules surrounding the dust particle are in constant, random motion. • When they hit the dust particle, they push it in random directions

11. Matter in motion • The idea that the particles (atoms and molecules) of all matter are in constant, random motion is called the kinetic theory of matter.

12. Kinetic Theory of Matter • All matter is made of atoms and molecules. • These particles are always in motion. • The higher the temperature, the faster the particles move. • At the same temperature, heavier particles move slower and lighter particles move faster.

13. Temperature and Heat • What makes hot tea different from cold iced tea? • Same particles • movement of particles is different • Higher temp = faster moving particles

14. Temperature and Heat • Lower the temperature and the particles slow down. • At very low temperatures the motion of the molecules is very slow. • You cannot make things so cold that the motion completely stops, but . . .

15. scientists have come close. The temperature at which the particles of matter would completely stop is called absolute zero.

16. Absolute zero is - 273.15° C You can’t get colder than that, no matter how hard you try

17. Transfer of heat • When hot matter touches colder matter, faster moving particles collide with slower moving particles. • The faster moving particles give some of their energy to the slower moving particles.

18. Matter in the solid state • In a solid, the particles vibrate or shake back and forth • but do not move from their position in respect to each other.

19. The particles vibrate about a fixed position.

20. Crystals or Crystalline Solids • Particles of crystals are arranged in repeating geometric patterns

21. Table salt crystals are shaped like cubes.

22. Diamond, a form of carbon, is also a crystalline solid. • the crystals are shaped something like pyramids.

23. Non-crystalline solids • Many solids do not form crystals. • Their molecules do not arrange into repeating patterns • often because they are too large. • Examples: • glass • many plastics

24. How does a solid become a liquid? • Start with very cold ice and gradually heat it. If you could see the molecules, you would see each molecule shaking faster and faster, • but still held in one position by the other molecules around it.

25. Keep heating your ice • When the temperature reaches 0° C, the molecules begin to break free. • The molecules begin to move freely around each other. • The molecules enter the liquid state.

26. Melting point = the temperature at which a substance changes from a solid to a liquid.

27. Temperature (C°) 60° 20° 0° -20° 0 Heat (kilojoules)

28. Temperature (C°) 60° 20° 0° -20° 0 Heat (kilojoules)

29. The amount of heat required to melt 1 kg of a solid is called its heat of fusion measured in kilojoules per kilogram kJ/kg

30. heat of fusion Temperature (C°) 0° Heat (kilojoules)

31. Water’s heat of fusion is 334 kJ/kg • That is the same amount of energy you would spend if you climbed all the stairs in a 110-story tall building. No, not a 110-foot tall building . . . a 110-story building!

32. Freezing • As you know, if you can melt something, you can cool the liquid again to freeze it. • When you cool a liquid, the particles begin to slow down. • The attractive forces between the particles begin to catch the particles, and crystals begin to form.

33. Freezing point = • the temperature at which attractive forces trap particles in a cooling liquid and form crystals. Think: If the melting point of iron is 1,535° C, at what temperature does iron freeze?

34. Non-crystalline solids • Non-crystalline solids, like glass, butter or wax, do not have a definite freezing or melting point. • If you slowly heat cold butter, it gradually gets softer and softer until it is completely liquid.