1 00:00:00,000 --> 00:00:06,820 Unit 7. Light, Sound, Materials and Structures. Second Grade. 2 00:00:08,199 --> 00:00:16,420 1. Light and Sound. What is light? Properties of light. What is sound? Properties of sound. 3 00:00:17,519 --> 00:00:26,339 2. Materials. Materials. Natural and man-made materials. Properties of materials. 4 00:00:26,339 --> 00:00:29,579 3. Structures 5 00:00:29,579 --> 00:00:31,559 What is a structure? 6 00:00:32,560 --> 00:00:34,219 Conditions for a good structure 7 00:00:34,219 --> 00:00:38,439 1. Light and sound 8 00:00:38,439 --> 00:00:42,100 What sense do you use to perceive light? 9 00:00:43,119 --> 00:00:45,159 What sense do you use to perceive sound? 10 00:00:46,240 --> 00:00:48,759 We use our sense of sight to see light. 11 00:00:49,439 --> 00:00:52,119 We use our sense of hearing to hear sounds. 12 00:00:53,299 --> 00:00:54,359 What is light? 13 00:00:54,359 --> 00:00:59,219 Light is a type of energy. It helps us see things. 14 00:01:00,719 --> 00:01:06,799 Light sources are things that emit light. Some are neural like the sun, lightning, and stars. 15 00:01:07,900 --> 00:01:12,140 And others are artificial, like a flashlight, a light bulb, or a television. 16 00:01:13,680 --> 00:01:14,680 Properties of light 17 00:01:14,680 --> 00:01:18,379 It moves in a straight line, a ray of light. 18 00:01:19,060 --> 00:01:23,420 It is faster than sound. In a storm, first you see the lightning. 19 00:01:24,359 --> 00:01:25,980 Then, you hear the thunder. 20 00:01:27,159 --> 00:01:30,480 Reflection, it bounces and goes to the opposite direction. 21 00:01:31,719 --> 00:01:34,239 Some objects block the light and others don't. 22 00:01:35,719 --> 00:01:38,040 Shadows happen when something blocks the light. 23 00:01:39,260 --> 00:01:41,599 Transparent, light can pass through it. 24 00:01:42,799 --> 00:01:45,420 Translucent, some light can pass through it. 25 00:01:46,480 --> 00:01:48,680 Opaque, light can't pass through it. 26 00:01:50,239 --> 00:01:51,480 What is sound? 27 00:01:52,280 --> 00:01:54,140 Sound is a type of energy. 28 00:01:54,359 --> 00:01:58,359 It helps us hear noises, music and voices. 29 00:01:58,359 --> 00:02:02,359 A source of a sound is what makes that noise. 30 00:02:02,359 --> 00:02:06,359 Some are natural, like a river, a bird or thunder. 31 00:02:06,359 --> 00:02:11,360 And others are man-made like an airplane, a speaker or an explosion. 32 00:02:11,360 --> 00:02:14,360 Properties of sound 33 00:02:14,360 --> 00:02:18,360 It moves in a waves through air, water and solids. 34 00:02:18,360 --> 00:02:22,360 Sound vibrations have two characteristics. 35 00:02:22,360 --> 00:02:26,060 Pitch, high pitch, whistle or low pitch, drum. 36 00:02:27,080 --> 00:02:30,580 Volume, high volume, loud or low volume, soft. 37 00:02:32,400 --> 00:02:35,620 Practice, match the correct sentence with the picture. 38 00:02:35,620 --> 00:02:41,550 2. Materials 39 00:02:41,550 --> 00:02:43,349 Materials 40 00:02:43,349 --> 00:02:44,590 Wood 41 00:02:44,590 --> 00:02:46,090 Cardboard 42 00:02:46,090 --> 00:02:47,370 Paper 43 00:02:47,370 --> 00:02:48,830 Plastic 44 00:02:48,830 --> 00:02:50,210 Straw 45 00:02:50,210 --> 00:02:51,629 Rubber 46 00:02:51,629 --> 00:02:52,849 Glass 47 00:02:52,849 --> 00:02:54,270 Fabric 48 00:02:54,270 --> 00:02:55,469 Wool 49 00:02:55,469 --> 00:03:16,669 Leather, silk, cotton, stone, concrete, brick, diamond, clay, slate, metal, copper, iron, steel, bronze, silver, gold 50 00:03:16,669 --> 00:03:36,229 natural wood brick diamond clay slate rubber wool leather silk cotton straw metal man-made 51 00:03:36,229 --> 00:03:37,650 Concrete 52 00:03:37,650 --> 00:03:38,969 Glass 53 00:03:38,969 --> 00:03:40,370 Plastic 54 00:03:40,370 --> 00:03:41,669 Paper 55 00:03:41,669 --> 00:03:43,210 Cardboard 56 00:03:43,210 --> 00:03:46,819 Properties of materials 57 00:03:46,819 --> 00:03:49,539 Materials can be soft or hard. 58 00:03:50,580 --> 00:03:52,259 Materials can be rough or smooth. 59 00:03:53,319 --> 00:03:55,060 Materials can be rigid or flexible. 60 00:03:56,199 --> 00:03:58,199 Materials can be transparent or opaque. 61 00:03:59,680 --> 00:04:00,080 Practice 62 00:04:00,080 --> 00:04:02,300 Circle the correct words. 63 00:04:07,719 --> 00:04:09,680 3. Structures 64 00:04:09,680 --> 00:04:11,819 What is a structure? 65 00:04:12,439 --> 00:04:19,100 And structure is a group of elements that resists a load. A load can be 66 00:04:19,100 --> 00:04:26,759 the weight of the structure, weather, rain, wind, temperature changes, the weight of people, 67 00:04:27,019 --> 00:04:34,639 machines, furniture. Why do we build a structure? To create a separate space like a building, 68 00:04:34,639 --> 00:04:40,439 a house or a stadium. To connect two places, a bridge or an elevator. 69 00:04:40,439 --> 00:04:48,540 to resist the forces of nature a dam or a retaining wall conditions for a good structure 70 00:04:48,540 --> 00:04:56,480 a good structure doesn't break a good structure doesn't lose its shape a good structure has a 71 00:04:56,480 --> 00:05:03,579 function a good structure costs money materials and workers a good structure is beautiful 72 00:05:03,579 --> 00:05:07,079 the end you did it