3rd+Grade+Science

Skimmer - Force & Motion
Gravity - Earth pulls down on all objects with a force called gravity. With very few exceptions, objects fall to the ground no matter where the object is on the Earth. Force - A force is either a push or a pull. The motion of objects can be changed by forces. The size of the change is related to the size of the force. The change is also related to the weight (mass) of the object on which the force is being exerted. When an object does not move in response to a force, it is because another force is being applied by the environment. Speed - An object is in motion when its position is changing. The speed of an object is defined by how far it travels in a standard amount of time.

Earth Materials
Earth Materials - Earth materials that occur in nature include rocks, minerals, soils, water, and the gases of the atmosphere. Some Earth materials have properties which sustain plant and animal life. Surface Changes - The surface of Earth changes. Some changes are due to slow processes, such as erosion and weathering; and some changes are due to rapid processes, such as landslides, volcanic eruptions, and earthquakes. Using Earth Materials - Some Earth materials have properties that make them useful either in their present form or designed and modified to solve human problems. They can enhance the quality of life as in the case of materials used for building or fuels used for heating and transportation. Fossils - Fossils provide evidence about the plants and animals that lived long ago and the nature of the environment at that time.

Ecosystems
Life Requirements - Organisms have basic needs. Animals and plants need air, water, and food. Plants also require light. Plants and animals use food as a source of energy and as a source of building material for growth and repair. Interactions - Organisms interact in various ways including providing food and shelter to one another. Some interactions are helpful; others are harmful to the organism and other organisms. Changed Environment Effects - When the environment changes, some plants and animals survive to reproduce; others die or move to new locations. Natural Resources - The supply of many natural resources is limited. Humans have devised methods for extending their use of natural resources through recycling, reuse, and renewal. Human Impact - Humans depend on their natural and constructed environment. Humans change environments in ways that are helpful or harmful for themselves and other organisms.

Energy: Light, Heat, Sound
Forms of Energy - Heat, light, and sound are forms of energy. Light Properties - Light travels in a straight path. Shadows result from light not being able to pass through an object. When light travels at an angle from one substance to another (air and water), it changes direction. Sound - Vibrating objects produce sound. The pitch of sound varies by changing the rate of vibration. Conductive and Reflective Properties - Objects vary to the extent they absorb and reflect light energy and conduct heat. Energy and Temperature - Increasing the temperature of any substance requires the addition of energy.