教科版小学科学新版三年级下册科学第三单元《太阳、地球和月球》知识点.docx

教科版小学科学新版三年级下册科学第三单元《太阳、地球和月球》知识点 Unit Three: The Sun。Earth。and Moon Lesson One: 1.The Sun is a star that emits light and heat。providing Earth with light and warmth。The Moon reflects sunlight。does not emit light or heat。and is Earths satellite。orbiting around it. 2.The Sun and Moon are both spherical。but their surfaces are different. 3.Understanding that the distance een the Sun。Moon。and Earth is different. 4.Waynes diagram. Lesson Two: 1.Throughout the day。under the sunlight。the length and n of an objects shadow changes in a certain pattern。We notice that the shadow is long in the morning。short at noon。long again in the afternoon。and changes from long to short to long again。The n of the shadow rotates clockwise like a clock。from northwest to north。then to northeast. 2.The sundial is an ancient instrument for measuring time。The steps to make a sundial are: (1) find the n based on the Sun or compass。(2) Align and place the cardboard flat。(3) Erect a short pole at the center of the cardboard。(4) Draw the shadow on the cardboard. 3.Changes in the n of the Sun can cause changes in the shadow of an object。As the Suns n changes from low to high to low again。the shadows length changes from long to short to long again。Also。as the Sun rises from the east to the south。then to the west。the n of the shadow changes opposite to that of the Sun. Lesson Three: 1.When light is blocked while traveling。a shadow of the blocking object is formed。The ns for producing a shadow are a light source。blocking object。and a screen (the plane that receives the shadow)。The light source emits light。which shines on the screen。The blocking object blocks some of the light。and the area where the light cannot reach es dark。forming a shadow. 2.Changes in the light source and blocking object can cause changes in the shadows length。size。n。and shape。When we change the angle of the light source。the length and n of the shadow change。When we change the shape of the blocking object。the shape of the shadow chan