Physical Science – Grade 8

1. Physical Science – Grade 8 Chapters 10,11,12,18, 19

2. Structure of the Atom • Matter- anything that takes up space and has mass • Matter also has inertia • Atoms are the smallest units of matter

3. Subatomic Particles Atoms consist of a positively charged center, or nucleus, surrounded by negatively charged particles called electrons . The two major kinds of particles in the nucleus are protons and neutrons. Protons are positively charged particles. Neutrons carry no charge.

4. Masses of subatomic particles Subatomic particle/ charge Mass 1 atomic mass unit (u) 1 atomic mass unit (u) negligible • Proton • positive charge (+) • Neutron • Neutral (0 charge) • Electron • Negative charge (-)

5. Model of the Atom • In this model, electrons move around the nucleus in a region called the electron cloud. • What two subatomic particles are in the nucleus? What are their charges and masses?

6. Electrons and Their Energy Levels

8. Elements and Atomic Number • Element – A substance made up of only one type of atom • The atomic number for each element is the number of protons. • The number of protons are = to the number of electrons (in a neutral atom)

9. The Mass of an Atom • Protons + Neutrons = the Atomic Mass of the atom • Isotopes – atoms of the same element with different numbers of neutrons • The average atomic mass of an element is the average mass of the mixture of its isotopes

10. The Periodic Table • Elements are arranged according to increasing atomic number • A Chemical Symbol is a shorthand way of writing the name of the element.

11. The Periodic Table (continued) Vertical columns are called Groups (1-18) • Group 18 elements are known as Noble Gases Horizontal rows are called Periods (1– 7)

12. Metals, Metalloids & Nonmetals

13. Chapter 12 Elements and their Properties

14. Metals & Nonmetals

15. Coinage Metals Copper Silver Gold (Group 11)

16. Magnetic Metals Iron Cobalt Nickel (Period 4) Fun Fact: Did you know that the Canadian nickel can be magnetized? (The American nickel cannot)

17. Metalloids • Metalloids are located on the staircase between metals & nonmetals. • Metalloids have properties of both metals and nonmetals. Ex: Silicon has a metallic luster and is brittle Boron Silicon Germanium Arsenic Antimony Tellurium Polonium

18. Chapter 11 Chemical Bonds

19. Compounds A compound is two or more elements chemically combined. Compounds take on properties that are different than the elements that they consist of. The compound sodium chloride (salt) consists of the elements sodium & chlorine. Na + Cl Sodium Chloride

20. Chemical Formulas • A Chemical Formula is a shorthand for the compounds. • Subscript: Number “Written Below” that tells how many atoms of that element are present in the compound 1. How many atoms of Hydrogen are present in this chemical formula? 2. How many atoms of Oxygen are present?

22. Kinds of Chemical Bonds • A chemical bond is a force that holds together the atoms in a substance.

23. Kinds of Chemical Bonds • A chemical bond is a force that holds together the atoms in a substance.

24. CHAPTER 18 WAVES AND SOUND

25. CHARACTERISTICS OF WAVES • Waves- are rhythmic disturbances that carry energy through matter or space • Medium- A material through which a wave transfers energy

26. Transverse Waves – The medium moves at right angles to the direction the wave travel Parts of a transverse wave • Crest – The highest point in a wave • Trough- the lowest point in a wave • Wavelength - the distance from one successive crest to crest or trough to trough • Amplitude – the distance from the rest position to the crest or the rest position to the trough

27. Measuring Transverse Waves Frequency – is the number of wave crests that pass one place each second • Frequency is measured in Hertz (Hz) Wave Velocity- how fast a wave moves forward velocity = wavelength x frequency V = x F

28. DIAGRAM OF A TRANSVERSE WAVE Equilibrium position = Rest Position

29. Compressional Waves • Compressional Wave – matter vibrates in the same direction as the wave travels • Sound travels in compressional waves • A compressional wave is composed of a compression and rarefaction

30. Comparing Transverse & Compression Waves

31. Comparing Transverse & Compressional Waves

32. Moving Through Media The speed of sound waves depends on 2 things: • Medium through which waves travel • Temperature of the medium *Types of Media: 1. solids 2. liquids (best conductors of sound) 3. gases Speed of Sound = 761 m/h Speed of Light = 186,000 m/s Which one do you think travels faster?

33. Decibel Scale Loudness is the human perception of sound intensity. -The higher the intensity and amplitude, the louder the sound. The intensity level of a sound is measured in units called decibels (dB). Sounds with an intensity level about 120 dB may cause pain & permanent hearing loss.

34. Frequency and Pitch Pitch – the highness or lowness of a sound The higher the frequency, the higher the pitch The lower the frequency, the higher the pitch

35. The Doppler Effect is defined as the change in frequency & pitch of a sound as a result of motion. The pitch of the emergency vehicle’s siren is higher when the vehicle is approaching because the wave crests are closer together. Why does the sound have a lower pitch after the vehicle has passed?

36. Using Sound Waves! • Ultrasonic (above 20,000 Hz) • high-frequency waves • Used in sonar (sound navigation ranging) • Medical uses • Infrasonic (below 20 Hz) • Heavy machinery • Thunder • Body rumblings

37. Fun Fact Bats can detect sounds as high as 100,000 Hz

38. Music to Your Ears Music- created using specific pitches- sound quality followed by a regular pattern Noise- no set pattern, no definite pitch

39. Music… Continued • Resonance- the vibrating of an object at its natural frequency • Sound Quality- the difference among sounds of the same pitch and loudness • Interference- ability of 2 or more waves to combine and form a new wave • Reverberation- many reflections of a sound • Acoustics- the study of sound

40. Chapter 19 - LIGHT

41. Electromagnetic Radiation • Electromagnetic Waves are transverse waves produced by the motion of electrically charged particles • Electromagnetic Radiation is the transfer of energy by electromagnetic waves. - These can travel through a medium - These waves can also travel through a vacuum at 300,000 km/s (186,000 m/s)

42. Electromagnetic Spectrum • Electromagnetic Spectrum- the arrangement of waves according to wavelength & frequency • Photons- tiny, particle-like bundles of radiation

44. Types of Radiation Gamma Waves have the highest frequency and are the most penetrating. They can cause cancer and they can cure cancer.

46. Do you ever wonder…. how popcorn kernels pop so quickly in the microwave???

47. Light & Matter

48. Colors Why does grass appear green? Why is the sky blue? The color that you see is the wavelength of the colors that are reflected to your eye. The remainder of the colors are absorbed by the object. White = reflection of all colors Black = absorption of all colors

49. Kinds of Lighting Green Fact: The country is now turning over to LED Lighting, due to less energy use and more brightness.

50. Properties of Light