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Rabu, 11 Mei 2016

Science Summary 2nd Semester for Grade 4

Three forths of the earth is covered by oceans, lakes and rivers.
When a cloud is so low that it is at ground level, we call it fog.

A stratus cloud that is very close to the earth's surface. They are flat and thick layers of clouds that look like a blanket.

Matter is anything that takes up space and has weight.
A molecule is the smallest piece of a substance that still has all the qualities of that substance.

Every water molecule is made of two atoms of hydrogen and one atom of oxygen (H2O).
Molecules in solids are packed very close together.
Matter that has no shape and does not fill up a certain amount of space is a gas.

Matter that has no shape and does not fill up a certain amount of space is a gas. Many gases are colorless. Air is a mixture of gases.
Molecules in gases are far apart and are the fastest moving molecules.

Because water has such a high degree of surface tension, objects which are heavier than water will float on the surface unless the surface film of the water is broken.
When solids are heated, the molecules begin to move more rapidly.

212 degrees Fahrenheit (100 degrees C)is the boiling point of water.
Water that is colder than 32 degrees Fahrenheit (0 degrees C) has completely changed to a solid - ice.

Energy is the ability to do work. Force is a push or a pull on an object. Gravity is the force which draws things down toward the center of the earth. In order for you to lift something, you must exert more force than gravity does on that object.

Nitrogen makes up most of the air. Air is made up of 78% nitrogen .
The weight of all the air in the atmosphere creates pressure as it presses down. Air pressure is greatest close to the surface of the earth.

The air surrounding the earth goes up to about 1000 miles above the Earth. Earth's gravity holds the atmosphere in its place and keeps air from floating off into outer space.

The earth and its atmosphere are constantly exchanging water. As water moves from the earth to the air and back again, it changes from a liquid to a solid or a gas. This process is called the water cycle.

The amount of water vapor, or humidity, in the air is changeable. The process by which liquid water becomes water vapor is called evaporation. The word relative humidity is used to describe the amount of water vapor in the air in relation to the temperature.

Because cool air cannot hold as much water vapor as warm air can, the water vapor begins to turn back into very tiny droplets of liquid water. This process is called condensation.

The temperature at which water condenses is called the dew point.
Any form of water which falls from the clouds to the earth is called precipitation. When falling rain or melted snow passes through a layer of very cold air, it freezes into little, hard, solid balls of ice called sleet.

The water droplets evaporate, and the vapor freezes into tiny crystals of ice. As more vapor continues to freeze, the ice crystals join together. This forms a snowflake. Hail is particles of ice which fall from the sky during some thunderstorms.

Nimbus means "rain," or "storm". Nimbostratus clouds are dark, gray sheets of rain clouds. Air mass is a large body of air which has the same temperature and humidity.

Equator: The imaginary line around the earth that is exactly halfway between the North and South Pole. A half of a sphere called hemisphere. Sphere, round like a ball.
Circumference is the distance around outside of an object, and the distance across the center of a circle called diameter. Rotation is the spinning motion of the earth.

The imaginary line that runs through the earth from Pole to Pole called Axis. To move in a circle around another object: Revolve.
Orbit is the pathway which the earth follows.

Pacific ocean: Largest and deepest ocean.
Atlantic ocean: The saltiest ocean.
Indian ocean: The warmest ocean.
Artic Ocean: The coldest and smallest ocean.

Continent: A large area of land rising out of the oceans.
Asia: The largest continent.
Australia: The smallest continent, known as "Island Continent"
Geologists: Scientists who study the earth.

Delta is a deposit of sand and soil, usually in a triangular shape, at the mouth of some rivers.
Salmon, a fish that leaves the ocean and goes to the stream where it was born to lay its eggs.
Wind causes what to happen in the water? waves.
Blue Whale, Dolphin, Porpoise are mammals

North Star is a star used to find direction because it is the brightest and is directly above the North Pole. Southern Cross is the most famous smallest constellations that points to the South Pole.
Sun is the closest star makes it appear brighter than any other star.
Day of creation that God created the moon, stars, and sun: day 4.



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