Science Study Guide for the GACE

Space Science

Space science, or astronomy, is the study of objects and phenomena beyond Earth. It includes everything from the nearby moon to distant stars and galaxies. This section covers some of the features of our solar system and explains how the positions and motions of Earth, the moon, and the sun affect our planet.

The Solar System

The solar system includes the sun and all of the objects that orbit it. This includes planets, asteroids, comets, dwarf planets, and other objects. Our solar system formed from dust and gas that condensed due to the gravity of the sun; the dust and gas left over combined over millions of years to create planets and other bodies.

The Planets

Our solar system includes eight planets. The four closest to the sun are small, rocky planets, also called terrestrial planets. They include Mercury, Venus, Earth, and Mars. The outer four planets are large planets composed mostly of gases and ices. Jupiter and Saturn are gas giants, while Uranus and Neptune are ice giants. In addition to the eight planets, the solar system contains recognized dwarf planets. A dwarf planet orbits the sun and is nearly round, but it has not cleared other objects from its orbital region.

The Sun, Earth, and Moon

Understanding the sun, Earth, and moon system is important in understanding several phenomena we experience on Earth. Day and night, seasonal cycles, phases of the moon, and tides can all be explained by the positions of the Earth, moon, and sun.

Relative Positions

Earth is the third planet from the sun, about 150 million kilometers (93 million miles) away. The moon is only about 384,000 kilometers (239,000 miles) away from Earth. The sun and moon appear to be a similar size in our sky, but that is just the effect of one being much closer than the other.

Motion

Rotation occurs when an object spins on its axis. Revolution occurs when one object orbits another. The sun, Earth, and moon all rotate on an axis. Earth’s axis is tilted. Earth revolves around the sun, and the moon revolves around the Earth. These basic motions cause the phenomena listed below:

Seasons— The tilt of Earth’s axis as it revolves around the sun causes different regions to receive more direct sunlight and longer periods of daylight at different times of the year. This creates the seasonal cycles experienced in the northern and southern hemispheres of the Earth.

Phases of the Moon— The moon reflects light from the sun. As the moon revolves around Earth, the amount of reflected light we can see changes. At the new moon, the light side of the moon is pointed away from us, so we can’t see the moon at all. At the full moon, we can see all of the light side of the moon. Between these two phases, the visible, illuminated portion of the moon waxes (appears to grow) or wanes (appears to shrink).

Tides— Tides are caused by the moon’s gravity pulling on Earth’s waters. The side of the Earth facing the moon will experience high tide, as will the side directly opposite.

Retrieved from: https://openstax.org/books/astronomy-2e/pages/4-6-ocean-tides-and-the-moon

Eclipses— Sometimes the Earth, moon, and sun line up in such a way that an eclipse occurs. A solar eclipse occurs when the moon moves in front of the sun, blocking light from the sun and casting a shadow on the Earth. A lunar eclipse occurs when the Earth moves between the sun and moon, casting a shadow on the moon.

Cycles and Patterns

The environment is shaped by the day and night cycles, weather, and climate. The landscape, plants, and animals adapt to the conditions around them, as do people. For example, the way of living, culture, and customs in the desert are different than those in the Mediterranean.

Science and Engineering

As with all science, Earth and space science relies on the scientific processes of asking questions, gathering data, carrying out investigations, analyzing data, and constructing conclusions. One important aspect of Earth and space science is the reliance on special equipment to make observations. This includes instruments such as telescopes, seismographs, satellites, radar, and more. Another important practice is model-building. Models help scientists explain and predict how Earth’s systems work. Models can be physical, mathematical, or computer-based.

Physical Science

Sciences can be distinguished by the subject that is being studied. In the case of physical sciences, the subject of study is inanimate (nonliving) objects. Sciences within physical sciences include astronomy, chemistry, physics, and Earth science.

Matter

Matter is anything that has mass and volume. Matter exists in different states, including solid, liquid, gas, and plasma. Its state depends mainly on temperature and pressure.

Composition and Structure

Matter is made up of small units called atoms that can be combined chemically or physically to create an endless variety of materials. Elements are made up of one type of atom, compounds are made of atoms chemically combined in a set ratio, and mixtures are several materials combined physically and not in a set ratio. The composition of a piece of matter will determine its properties.

Properties of Matter

Every object is made of matter and possesses a set of properties, which are traits that can be measured. There are many ways of classifying properties. They can be classified as extensive if they depend on the amount of material (e.g., length, volume), or intensive if they do not depend on the amount of material measured (e.g., density, temperature). Properties can also be physical if they can be observed without changing the substance into a different substance, such as mass or viscosity. Chemical properties, such as flammability, describe a substance’s ability to undergo a chemical change. Matter can be described precisely by listing a complete set of its properties.

Physical vs. Chemical Changes

Matter can transform into other types of matter. Physical changes are those that can occur without changing the chemical nature of the substance. Phase changes are physical changes. For example, water can freeze or evaporate without changing its chemical structure. Other physical changes include changes in shape, changes in size, and the creation or separation of a mixture. Chemical changes are those that change the chemical nature of the substance, and they involve a chemical reaction. Combustion, corrosion, decomposition, and cooking are examples of chemical changes. They create new substances with different properties from the original as the chemical bonds are broken and reformed.

Forces

A force is a push or pull that is exerted on an object. Forces cause objects to move, sometimes through direct contact and sometimes at a distance. Forces vary in strength and direction, and the combined forces acting on an object determine whether it will move and in what direction.

Friction

Friction is a force of resistance between two objects in contact with each other. In order to move an object, the force of friction must be overcome. The force of friction depends mainly on how strongly the surfaces are pressed together and on the materials and textures of the surfaces.

Gravity

Gravity is a force that acts at a distance on objects. The force of gravity depends on the mass of the objects involved and the distance between them. The gravitational attraction between two objects becomes stronger as their masses increase and weaker as the distance between them increases. Weight is a measurement of the force of gravity on an object. In order to lift an object off the ground, the force exerted must be stronger than the force of gravity. Gravity also causes flying objects to eventually fall back down to Earth, unless a constant upward force is exerted, like in an airplane.

Magnetism

Magnetism is another force that can act at a distance. A magnetic field is created by moving electric charges. The motion of the liquid metal in Earth’s core creates Earth’s magnetic field. Magnetic fields can attract certain materials. Iron, nickel, and cobalt are metals that respond to magnetic fields. Magnetic fields have north and south poles. Opposite poles attract and like poles repel each other.

Simple Machines

Simple machines are devices that make tasks easier by changing the size or direction of an applied force. They may reduce the force needed by increasing the distance over which the force is applied, but they do not reduce the total amount of work in an ideal system. Many everyday devices are made up of one or more simple machines.

Lever

A lever is a stiff bar that pivots around a fulcrum. A lever includes a fulcrum, an applied force, and a load. Their positions vary among different types of levers. A seesaw is one example in which the fulcrum is between the applied force and the load. The lever makes it possible to use the force of gravity on one person to lift the person on the other end. Other examples of levers include crowbars, brooms, tweezers, and scissors.

Wheel and Axle

A wheel and axle is a simple machine that helps apply force over a larger distance. The axle is a small rod to which a turning force is applied. The wheel attached to the axle spins and magnifies the distance over which the force is applied. The wheels on a bicycle work this way—the movement of the gears causes the wheel’s axle to turn, making the bike travel. Another way to use a wheel and axle is to apply a force to the wheel, making it easier to turn the axle. A doorknob is an example of this. The knob is a larger wheel that turns the smaller lock mechanism inside the door.

Pulley

A pulley is a simple machine that can change the direction of an applied force, making it more convenient to lift an object. Lifting a box off the ground is easier if you can use the force of gravity to pull downward instead of lifting the box directly upward. A system of several pulleys can be used to not only change the direction of the force, but also to require less total force to lift an object. A common example of a pulley is one used on a flagpole.

Inclined Plane

An inclined plane is a flat, slanted surface that makes work easier by spreading out the force required to move something over a greater distance. To lift items into a moving truck, for example, a ramp is typically used. This spreads out the effort required to lift the items up. The longer the ramp, the easier it is to raise the object. Ramps, stairs, and slides are examples of inclined planes.

Wedge

A wedge is made of two inclined planes joined together to form a point. It concentrates the force applied into a small point in order to cut or separate materials more easily. Some examples of wedges are knives, axes, nails, and chisels. A nail, for example, concentrates the force of the hammer hitting it into a sharp point that makes it easier to separate the wood fibers.

Screw

A screw is essentially an inclined plane, but it is wrapped around a cylinder. It makes work easier by increasing the distance over which the effort is applied. Think of a classic wood screw: each turn of the screw drives it deeper into the wood. This makes it easier to fasten the pieces together than it would have been without the grooves in the screw.

Energy

Energy is defined as the ability to do work or cause change. Energy allows objects to move, heat up, produce light or sound, or change in other ways. Every change in matter is powered by some type of energy.

Energy Sources

Some common forms of energy include:

• mechanical energy—This is the energy an object has due to its motion or position. Moving objects have kinetic energy, and objects that are in a position to move (such as at the top of a hill) have potential energy.

• radiant energy—This is the energy of electromagnetic waves, such as light, microwaves, ultraviolet waves, or infrared waves.

• thermal energy—This is the total energy associated with the motion of the particles in a substance. Faster-moving particles generally indicate a higher temperature.

• electrical energy—This is the energy of moving electric charges.

• chemical energy—This is the energy stored in the chemical bonds of a substance. Food and fuel, for example, store chemical energy.

• nuclear energy—This is the energy stored in the nucleus of atoms.

Energy Transfer

Energy can be transferred from one object to another. The mechanical energy of your foot moving through the air can be transferred to a soccer ball as you kick it. The thermal energy of a hot stove is transferred from the stovetop to the frying pan to the food that is being cooked. The radiant energy of the sun is transferred to Earth.

Energy Transformations

As energy flows through the environment, it can also change forms. Electrical energy can be transformed into radiant energy in a lightbulb. The chemical energy of gasoline is transformed into thermal and mechanical energy as a car moves. The potential energy of a roller coaster car at the top of a lift is transferred to kinetic energy as it falls down the track. The law of conservation of energy states that energy cannot be created or destroyed. The total amount of energy stays constant, even though it changes forms or is transferred from one object to another.

Light

As described previously, light is a type of radiant energy. It is part of the electromagnetic spectrum, which includes visible light as well as other types of energy that travel in waves. The visible spectrum describes the various colors of light. The color of light is determined by its wavelength, or the size of each wave. The acronym ROY G. BIV is often used to remember the colors of the visible spectrum in order from longest wavelength to shortest - red, orange, yellow, green, blue, indigo, and violet.

Sound

Sound is a type of mechanical energy in which vibrations are carried by the movement of matter. The vibration of a guitar string exerts a rhythmic pushing of air particles surrounding the string. The particles continue vibrating through the room, eventually reaching your ear where they are interpreted as sound. Lower-frequency vibrations are heard as a lower pitch, while higher-frequency vibrations are heard as a higher pitch. The vibrations lose strength as they move outward from the source. Sound can be carried through gas, liquid, and solid, but it cannot be carried through empty space.

Electricity

Electricity involves the movement of electric charges and is an important way to transfer energy over large distances. Electrical energy can be transformed into heat, light, sound, or motion. Power plants that create electricity can burn fuels such as coal, oil, gas, or biomass to transform chemical energy into electrical energy. Power plants can also use the motion of rivers, wind, or tides as well as the energy of the sun to generate electricity. Electricity travels through wires to individual homes and businesses where it is transformed into heat, light, or motion.