Milestone Key Concepts

Milestone

Key Concepts

From the 2020 State Study Guide

Updated with the 2024 Online Study Guide.

Force

This section will focus on developing a conceptual understanding of the relationship between force, mass, and the motion of objects. You will develop an understanding that all objects and substances in the natural world are composed of matter that is influenced by forces. You will explore the relationship between velocity and acceleration through graphical representations of the motion of objects. You will gain a qualitative understanding of the universal laws of motion through scenarios in which forces act through direct physical contact between objects as well as examples in which forces act on objects at a distance (via gravitational force)

Fill in the Blank

All objects and substances in the natural world are made of _____.

Displacement vs Distance

Displacement is the length and direction of a straight line between two locations, or positions. Since displacement considers only the length and direction of a straight line, it doesn’t depend on the actual path of a moving object. If Town A is 10 miles east of Town B, the displacement of Town A is 10 miles east relative to Town B. For a moving object, displacement can be defined as the change between the initial and final position of the object.

Distance is a measure of the length of a path that a moving object travels. If the only road between the two towns has to wind through hills, the distance traveled between the two towns is longer than 10 miles, even though the displacement between the two towns is 10 miles east.

Multiple Choice

Which term describes the how many miles you travel from your house to Ringgold Middle School?

• distance

• displacement

Speed vs Velocity

Speed measures the rate at which an object moves along a path. Unlike velocity, speed is not considered to have a direction.

Velocity is a quantity that measures the rate at which the position of an object changes in time. Velocity always describes a distance and a direction. Since velocity has direction, one way to show this numerically is to assume that travelling in a certain direction is symbolized with positive numbers while traveling opposite that direction is shown using negative numbers.

Fill in the Blank

What ONE thing makes velocity different from speed?

Acceleration

Acceleration is a quantity that measures the rate at which an object changes its velocity. People often talk about an object decelerating when the object slows down. An object that slows down is actually experiencing a negative acceleration. This means the rate of change is a negative value. An object can have a velocity but not acceleration if it is moving at a constant velocity.

Fill in the Blank

Acceleration is a change in _____.

This means that an object is changing its speed or direction.

Force

A force is a push or pull on an object. Force can be the result of contact, such as when you push a book across your desk. Examples of contact forces include frictional force, tension force, and applied force. Forces between objects that are not in contact with each other can be explained by the presence of force fields, like the magnetic field and the gravitational field. When one magnet repels another magnet, there is a push force that acts on the magnets even though the magnets are not in contact. Examples of forces at a distance are gravitational force, magnetic force, and electric force.

Multiple Select

Force fields...

• can apply a force to an object when they are not in contact with each other.

• include magnetic and gravitational forces.

• can be a push or a pull.

Electrical Force

The amount of electric force between two charged objects depends on the magnitude of the charges and the distance between them.

Charges can be positive (+) indicating a shortage of electrons, or negative (-) indicating a surplus of electrons.

The greater the difference in charge, the greater the stored energy in the electric field.

Electric force decreases as the distance between charged objects increase.

This same concept applies to magnetic force.

Fill in the Blank

For both magnetic force and electric force, the further apart the objects are, the ___ the force is between them.

Balanced vs Unbalanced

When two or more forces act on an object but the object’s velocity does not change, the object is being acted on by balanced forces. A book on your desk that is not moving is said to be stationary. The book is said to be at rest in relation to the desk. Gravity is acting to pull the book down. The desk pushes up against the book, and the book is at rest in relation to the desk.

An accelerating object is being acted on by unbalanced forces. When you push your book across your desk, you are applying force to one side of the book. The force of friction acts on the book in the opposite direction that the book is moving, reducing the speed at which the book moves. Because the book begins to move in the direction you are pushing it, these forces are unbalanced.

Multiple Choice

Moving objects...

• can have balanced forces acting on them.

• can have unbalanced forces acting on them.

• could have balanced or unbalanced forces acting on them.

• do not have forces acting on them.

Fill in the Blank

An object with unbalanced forces acting on it will be _____.

Friction and Inertia

Friction is the force that resists motion between two surfaces.

Inertia is the resistance to any change in the state of motion of any physical object. All matter has inertia, and the inertia of matter does not change until the matter is acted on by unbalanced forces that cause a change in motion.

Fill in the Blank

Compare friction and inertia.

Both involve the _____ of motion.

Mass and Gravity

Mass is the total amount of matter of an object. Mass is a numerical measure of the object’s inertia. The mass of an object does not change, regardless of where the object is located.

Gravity is the force of attraction that exists between any two or more masses. Gravity can refer to the force that Earth exerts on everything. Gravity also refers to the gravitational force every object exerts on every other object.

Fill in the Blank

All objects with _____ exert a gravitational force on all other objects.

Structure and Properties of Matter

In this section, you will develop a conceptual understanding of the nature of matter. You will understand that, in a chemical reaction, matter can be neither created nor destroyed, only transformed. You will learn about the characteristics of matter (i.e., physical and chemical properties) that are useful to classify and differentiate substances.

Fill in the Blank

In a chemical reaction, _____ cannot be created or destroyed, only transformed.

Matter.

Matter is anything that takes up space and can be weighed. So matter has volume and mass. Matter is made up of small particles, much too small to be seen, but these particles combine in large numbers to make up objects that are big enough to be seen. Things that cannot be seen are also matter - many gases are colorless and transparent, like air. Yet air is present, takes up space, and has mass because it is composed of atoms and molecules. The way the particles that make up an amount of matter interact with each other describes the form, or state, of matter.

Multiple Select

Air is matter.

• True because it is composed of atoms and molecules.

• True because it takes up space.

• False because it is colorless and transparent.

• False because we cannot see it.

Atoms, Elements, and Molecules.

Atoms are the smallest unit of matter that defines the chemical element.

Elements are pure chemical substances that are made up of one type of atom.

A molecule is made of two or more atoms joined together chemically. Molecules can be made of the same element or more than one element. Water molecules are made up of two atoms of hydrogen and one atom of oxygen.

Multiple Select

Molecules...

• are made of one type of atom.

• are made of more than one type of atom.

• are chemically combined atoms.

• always are part water.

Periodic Table

The Periodic Table of Elements is a table arranging all the known elements into groups with common properties. This arrangement also demonstrates trends based on those properties.

Multiple Choice

The periodic table includes all the known _____.

• elements

• atoms

• molecules

• types of matter

Fill in the Blank

The periodic table is arranged in _____ by similar properties.

Compounds vs Mixtures

Substance is matter of any form that cannot be broken down into separate elements by physical means but can be broken down using chemical changes.

A compound is a pure chemical substance that is made up of two or more different elements. Salt is a compound whose molecules are made up of one atom of sodium and one atom of chlorine.

A mixture is made of two or more substances that are not combined chemically. Salted popcorn is an example of a mixture.

Multiple Choice

What is the difference between compounds and mixtures.

• Compounds are made of more atoms than mixtures.

• Mixtures are made of more atoms than compounds.

• Compounds are combined physically and mixtures are combined chemically.

• Mixtures are combined physically and compounds are combined chemically.

States of Matter

Matter is anything that has mass and occupies space. Matter can be found in several states (e.g., solid, liquid, gas, plasma).

The states of matter are the different forms that matter can be found in. Water is a liquid, the state of matter that has a definite volume but no fixed shape. When water is ice, it is a solid. Solids have a definite shape and volume. Their shape and volume cannot be easily changed. When water is steam, or water vapor, it is a gas. Gases have no definite shape and take the shape of their container. Plasma is gas that is charged. Plasma conducts electricity easily. Stars and neon lights are examples of plasma. Plasma is different from the other states of matter in that it is a high-energy state of matter.

Important Tip

The movement of particles within the different states of matter can vary greatly. Particles in solids are packed together very tightly, and they do not move around easily. This is why solids tend to be hard. Particles in a liquid move around and are packed loosely. Particles in gases move in all sorts of directions, and the particles are spread very far apart.

Multiple Select

What properties make the states of matter different?

• fixed or no fixed shape

• speed of particles

• definite or no definite volume

Physical Properties

Physical properties are any properties that are measurable and can be observed. Physical properties can be determined without changing the chemical properties of an object. Color, hardness, area, length, strength, temperature, and state of matter are some examples of physical properties.

Fill in the Blank

Physical properties can be observed and _____ without changing the object.

Examples of Physical Properties

Volume is the amount of space that an object or substance occupies. Volume is a physical property.

Density is the physical property that describes how tightly matter is put together. A pure element, such as gold, will have a characteristic density and mass.

Boiling point is the physical property that describes the temperature at which a substance will change from a liquid to a gas. Water boils at 100°C (212°F).

Melting point is the physical property that describes the temperature at which a solid will become a liquid. Ice, a solid, will change into liquid water at 0°C (32°F). This is the melting point of water.

Multiple Select

Select the physical properties.

• density

• volume

• melting point

• boiling point

Chemical Properties

Chemical properties are any properties that can be measured only by chemically changing an object. Paper starts to burn at around 249°C (480°F). At this temperature the paper combines with oxygen in the air and new substances are formed.

Multiple Choice

Chemical properties _____ be observed without testing.

• can

• cannot

Examples of Chemical Properties

Combustibility is the chemical property of how easily a substance will set on fire. For example, paper’s heat of combustion is around 249 degrees Celsius.

Reactivity is the chemical property of the capacity of an atom or molecule to go through a chemical reaction with another atom or molecule. Sodium is a very reactive metal. Sodium reacts rapidly and energetically with other substances. Gold is a metal that is not very reactive. It won’t tarnish from oxygen or water.

Multiple Select

Select the chemical properties.

• combustion

• combustibility

• rusting

• reactivity

• oxidation

Types of Changes

A physical change happens when matter has a change in its physical properties but not its chemical properties. For example, salt can be dissolved in water, but if the water evaporates, the salt is still there.

A chemical change happens when matter breaks down into two or more substances or when more than one substance is combined to form a new substance. Hydrogen peroxide forming bubbles on its own is an example of matter breaking down into two substances. Vinegar and baking soda turning into bubbling foam is an example of two substances combining to create other substances.

Fill in the Blank

A _____ change will create something new.

Chemical Reaction and Precipitate

A chemical reaction is a process where two or more substances combine chemically in some way to form one or more other substances. When iron is combined with air and water, the iron is slowly converted into rust.

A precipitate is a solid that is formed by a chemical reaction. Precipitates can form in a solution or inside another solid.

Multiple Choice

A chemical reaction is a type of a chemical change.

• True

• False

Law of Conservation of Matter

The law of conservation of matter states that the total amount of matter in a system cannot be created or destroyed. When a piece of paper burns, it becomes ash, water vapor, and carbon dioxide. If the mass of the ash, water vapor, and carbon dioxide were found, it would be the same as the mass of the paper before the paper was burnt.

Fill in the Blank

During a reaction the total amount of mass before the reaction will _____ the total amount of mass after the reaction.

Energy and Force

In this section, you will develop an understanding that energy exists in many forms. You will learn that in a closed system, energy can be transferred and transformed, but the total amount of energy available is always the same—it is conserved. In addition, you will study the three types of transfer of thermal, or heat, energy: conduction, convection, and radiation. You will also learn about two of the four main forces in the universe: gravitational and electromagnetic forces. You’ll determine how these forces influence the motion of objects and are responsible for the work that a system does or for the work that is done on a system. Energy stored in electric and magnetic fields can result in forces.

Fill in the Blank

The total amount of energy in a closed system is always _____.

Multiple Choice

Energy stored in electric and magnetic fields can result in ___.

• more energy.

• forces.

• changing chemical properties.

• nothing.

Energy

Energy is the ability to do work.

Work means using a force to move an object some distance in the direction of the force.

Another way to look at it is that energy represents the ability to change something. Neither matter nor energy can be created or destroyed, but both can change into different forms.

Law of Conservation of Energy

The law of conservation of energy states that the total amount of energy in a system cannot change unless energy enters or leaves that system by some form and that energy cannot be created or destroyed. Energy can only change forms. An energy transformation refers to the changing of energy from one form to another.

Multiple Select

Energy can...

• be created.

• be destroyed.

• be transferred.

• change forms.

PE and KE

Gravitational potential energy is the energy stored in an object due to its position. The energy stored in a ball sitting at the top of a ramp is all potential energy. In the case of the ball, gravity is pulling down on the ball. Although the ball is not rolling down the hill, it has potential energy due to the pull of gravity.

Kinetic energy is the energy of motion. As the ball starts to roll down the ramp, the potential energy of the ball transforms into kinetic energy. The energy in the system is converted from potential energy to kinetic energy.

Multiple Choice

What type of energy do all moving objects have?

• Kinetic

• Potential

• Thermal

More About Energy

Since energy is the ability to do work, sometimes energy is stored, so we do not see the effects of the energy, yet it is still there. Some types of stored energy are chemical energy, thermal energy, and the energy stored in magnetic and electric fields.

Multiple Choice

You can always see the effects of energy.

• True!

• False, sometimes energy is stored.

More Types of Energy

Mechanical energy is the total of all the potential energy and kinetic energy in an object.


Light energy is a form of electromagnetic radiation, which is a form of energy that is produced by oscillating electric and magnetic disturbances or by the movement of electrically charged particles traveling through a vacuum or matter.

Electrical Energy

Electric energy is the energy of electrons moving through a conductor. Electricity is the name for the motion of electrons along the path formed by a conductor.

Electrical energy in a wire of a complete circuit can create a magnetic field that produces a magnetic force that can move a compass needle. This effect can be scaled up and combined with other factors. This principal can be used to construct electromagnets that can produce tremendous amounts of magnetic force.

Fill in the Blank

Electrical energy is when ___ move through a conductor.

Thermal Energy

Thermal energy (also called heat energy) is the random motion of particles (whether vibrations in solids or molecules in free motion in a gas). This energy is distributed among all the particles in a system through collisions and interactions at a distance. Thermal energy flows from an object that has a higher temperature to one that has a lower temperature.

Multiple Choice

Thermal energy flows from an object with a _____ temperature to an object with a _____ temperature.

• higher, lower

• lower, higher

• higher, same

• lower, same

Heat Transfer

Conduction is the movement of heat through an object or from one object to another when they are touching. In conduction, thermal energy is transferred between atoms when they collide with each other. Thermal energy moves from warmer areas, those with higher energy, to cooler areas, those with less

energy. This is why ice in a glass of water melts on a warm day. Warm air molecules collide with the molecules of the glass container and transfer thermal energy to them. The molecules in the container then

pass the thermal energy between themselves by direct contact. Finally, the energy is transferred to the water and ice by the water molecules coming in contact with both. The thermal energy flows toward the ice and the energy turns the ice into water.

Heat Transfer Continued

Convection is the movement of heat through fluids and gases. In convection, thermal energy is transferred due to differences in density caused by temperature variations. When you heat a pot of soup, the liquid becomes warm through convection. As the liquid at the bottom of the pot becomes warmer, its density decreases. The increased thermal energy causes the molecules to move faster, which spaces them farther apart, increasing the volume and thus decreasing the density. The change in density causes the warm liquid to rise to the top of the soup and the colder liquid to sink. It is this motion of the warm and cold masses that is called convection.

More Heat Transfer

Heat can also move by means of radiation. Thermal radiation does not require any form of matter to move through, as conduction and convection require. Thermal radiation energy moves via electromagnetic waves. Because of this, thermal radiation moves very fast.

Multiple Choice

Which type of heat transfer involves motion of particles due to density differences?

• conduction

• convection

• radiation

Multiple Choice

Which type of heat transfer will heat something the fastest?

• conduction

• convection

• radiation

Magnetic Energy

Magnetic energy is produced when magnetic fields are generated. Magnetic materials have what are known as magnetic domains—they are sort of like pieces of a big puzzle, as shown in the illustration of magnetized material below. The two poles of a magnet result when these magnetic domains align in such a way that they point in the same direction. If you cut a magnet in half, the domains of each half will still line up so that the two new magnets each have a north pole and a south pole. In an object that is not magnetized, the domains lie in many different directions and mostly cancel each other out.

Multiple Choice

Which pictures is showing an object that is magnetized?

Electromagnet

An electromagnet is created when a wire is coiled and an electric current flows through it. Generally, electromagnets have a metal core that helps to increase the strength of the electromagnet. Magnetic force is created by the movement of electrical charges through a wire. A magnetic field is created around the wire, and this magnetic field lines up the domains in the core, turning the core into a temporary magnet. When the electric current is turned off, the magnetic field quickly fades. An electromagnet can be made using a circuit with a battery, a switch, and wire wrapped around a nail.

Multiple Select

What is the purpose of an electromagnet?

• to create a temporary source of electricity

• to create a temporary electric field

• to create a temporary magnetic field

• to create a temporary magnet

Important Tip

When thinking of energy transforming from one form to another, remember that, in most cases, it is not a matter of one form of energy being transformed into only one other form of energy. When you rub your hands together, the kinetic energy of your hands is transformed by friction into heat energy. You can also hear your hands rubbing together, which is the result of the friction converting some of the kinetic energy into sound energy.

Multiple Choice

When energy transforms from one form to another, what is the result?

• only one form of energy

• always two forms of energy

• could be many forms of energy; it depends on the system

Waves

In this section, you will acquire a conceptual understanding of the nature of sound and electromagnetic radiation. You will study how sound behaves in the presence of different obstacles and how light is manipulated by positioning mirrors and lenses in its path.

Waves are constant fluctuations that travel through space (either in the vacuum of outer space or through matter), transferring energy. When you throw a rock in a puddle, the water forms waves that move outward from the place where the rock hit the water. Waves can move through solids, liquids, gases, and empty space (i.e., a vacuum, a volume containing no matter).

Fill in the Blank

Waves transfer _____.

Wave Properties

Frequency is the number of vibrations a wave makes per a unit of time, commonly measured in Hertz, which is waves per second. If you counted the number of wave peaks that occurred in a minute after

throwing a rock in a puddle, you could determine the frequency of that wave.

Wavelength is the distance from one peak of a wave to the next peak of the wave.

Amplitude is the property of a wave that describes half the distance between the height of the peak of the wave and the trough (the bottom) of the wave, or the maximum distance from the resting position. In a surf wave, the amplitude represents the amount of water displaced, which can be very large.

Multiple Choice

_____ is the height of the wave and _____ is the amount of waves per second.

• Frequency; amplitude

• Amplitude; frequency

• Wavelength; frequency

• Wavelength; amplitude

• Amplitude; wavelength

Important Tip

The ways waves travel is known as wave propagation. As waves propagate, some of the energy is transferred. When light travels through a glass of water, it slows down and is refracted. Some of the energy that is lost from the wave—and that causes the light to slow down—is transferred into the water and glass as thermal energy.

Fill in the Blank

Propagation is the way a wave _____.

Types of Waves

Electromagnetic waves do not require a medium to move through. Electromagnetic waves transport energy that is stored in the electric and magnetic fields.

Mechanical waves are caused by a disturbance or vibration that causes the molecules in matter to bump into each other and transfer the energy from one molecule to the next in a set direction. Mechanical waves require matter to provide a medium for the waves to move through, so mechanical waves cannot occur in the vacuum of space.

Multiple Choice

Which type of waves require a medium to move?

• mechanical waves

• electromagnetic waves

• both EM and mechanical

• neither EM nor mechanical

Electromagnetic Spectrum

Electromagnetic radiation is a form of energy that is produced by oscillating electric and magnetic disturbances, or by the movement of electrically charged particles traveling through a vacuum or matter. It is used to describe radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays.

The electromagnetic spectrum consists of all the different kinds of electromagnetic radiation. Radio waves have the smallest frequency and longest wavelength in the electromagnetic (EM) spectrum (the complete set of electromagnetic radiation) and therefore contain the least energy. Gamma rays have the largest frequency and shortest wavelength in the EM spectrum and therefore contain the

most energy.

Multiple Choice

Which part of the electromagnetic spectrum includes electromagnetic radiation?

• only x-rays and gamma rays

• only the visible light we can see

• none of it

• all of it

Sound

Sound is a mechanical wave that can be heard as it moves through a medium, such as air, and temporarily displaces the particles of the medium, either by rarefaction (the particles temporarily move farther apart, creating lower pressure) or compression (the particles temporarily move closer together, creating higher pressure). When fireworks go off on the Fourth of July, you can hear the sound. With some of the larger fireworks, you can also feel the air as the pressure from the firework exploding pushes the air away from the firework.

Multiple Select

Sound waves...

• are mechanical waves.

• need a medium to travel.

• have compressions and rarefactions.

• can be felt.

Light

When people refer to light, they are usually referring to the visible light they can see. Light is not considered matter and has no mass. The behavior of light can be explained by the introduction of a massless particle called a photon or by studying the way that electromagnetic waves interact with matter.

When the human eye sees colors, it is seeing the parts of the spectrum of light that are reflected from an object. A blue object reflects the wavelengths of light that we see as blue.

Fill in the Blank

Light is seen because it _____ off of objects.

Light Interactions

There are several processes that light can go through as it encounters matter. Reflection occurs when light bounces off a medium. Refraction occurs when light moves from one medium to a new medium and bends as the medium changes the speed of the light as it moves through the new medium. When you look through a glass of water and an object behind the glass appears to change shape, the light reflected by that object has been refracted by the glass. Diffraction occurs when light encounters an obstacle and slightly bends as it passes around the object. If you hold a CD and see the colors of the rainbow, this is the light being diffracted by the surface of the CD. Absorption occurs when light strikes a surface and the energy of the photon is taken up by the matter. An object lying in the sun will warm up as the sunlight transforms into heat energy.

Multiple Select

Which light interactions involve bending light waves?

• reflection

• refraction

• diffraction

• absorption