Density is the ratio of a substance's mass to its volume and can be expressed mathematically as
D=M/V.
Density results from the number of protons, neutrons, and electrons in the atoms that make up the substances and how closely they are arranged to each other either in the substance.
As the temperature of matter increases, its molecules move more rapidly and get farther apart. Solids, liquids, and gases expand as temperature increases.
https://youtu.be/liXT0UdHjDw
https://www.youtube.com/UM2prm3SDr0
Since the volume goes up, but the mass stays the same, density, therefore, must decrease as a function of increasing temperature.
When matter changes from a solid to a liquid, in most cases, the liquid will take up more space and thus be less dense. Likewise, when a liquid becomes a gas, the molecules spread out even more, and the density goes down even more.
Since mass stays the same, but volume increases, density must decrease as temperature goes up and as matter changes from solids to liquids and to gasses.
All matter in all creation responds to changes in temperature in several ways. One of those ways it in regard to its physical state. Depending on temperature, matter on earth will usually be either solid, liquid or gas (though two other states are possible under extreme conditions.)
Kinetic Theory Basic Assumptions
To understand why matter changes state, it is necessary to first understand temperature. To understand temperature, it is necessary to understand the basic assumptions of the Kinetic Theory of Matter. The first two assumptions are:
1. All matter is made of particles.
2. all particles of matter are in constant motion.
This means that in any sample, the molecules are moving. Because the molecules (particles) are moving, they have something called kinetic energy.
There is a formula for kinetic energy that relates kinetic energy to mass and velocity:
KE = 1/2MV2
The faster an object (of any size) moves, the more kinetic energy it has.
This formula models the observations that KE (kinetic energy) goes up as velocity increases. The Kinetic Theory of Matter says that the warmer something is, the faster the molecules go. Therefore, warmer molecules have more kinetic energy.
This is a key understanding for much of what follows with regard to states of matter.
The understanding of the Kinetic Theory of Matter leads directly to the definition of temperature, which is a part of the last two assumptions of kinetic theory.
Temperature is a basic measurement that is related to many of the concepts that will follow in the exploration of states of matter.
Temperature
The average kinetic energy of the molecules in a sample.
So, temperature can be understood as the average kinetic energy of the molecules as they move in constant motion.
With an understanding of temperature firmly established, the last two assumptions of the kinetic theory of matter can be understood:
3. The higher the temperature, the more kinetic energy they have, and the faster the particles are moving.
4. AND the faster they move, the more room they take up.
For example...
Temperature Scales
We measure temperature with a thermometer (A meter of the thermo.). A thermometer is placed in contact with a substance and the molecules of the substance bump into the thermometer until its molecules have the same average kinetic energy as the substance. When this occurs, the thermometer will indicate a temperature in one or more standard temperature scales.
Temperature scales that are commonly used include Fahrenheit, Celsius, and Kelvin. Most science relies on Celsius and Kelvin.
States of Matter: The state of matter depends on its temperature. When the average kinetic energy of the molecules is relatively low, then the matter will be observed as a solid. Extremely low temperatures beyond what is normal can result in another state of matter called a Bose-Einstein condensate, which will be discussed later. As the temperature goes up, matter will change into a liquid, then into a gas. At ultimately high temperatures, matter will be a plasma.
Solids
When in the solid state, matter has a definite shape and volume.
Solids, at any given temperature, will not change in shape or volume. The size and shape of a block of metal does not change unexpectedly.
This is because the molecules are bound to each other by forces that are stronger than the average kinetic energy of the individual molecules at that particular temperature. Though the molecules "wiggle" in place, they are not moving with sufficient energy to break the bonds that hold them in place.
As the temperature goes up, the wiggling will take up more space, and most solids will expand, but the shape will remain uniform and the increase in size is small by comparison to the size of the original.
Liquids
When in the liquid state, matter has a definite volume, but not a definite shape.
Liquids, at any given temperature, change shape to fit the container in which they are kept, but they retain their volume. Pouring a liquid from one container to another changes its shape, but does not change its volume.
The reason that liquids change shape is because the kinetic energy of the molecules exceeds the force that holds them together in the solid. But those forces still are strong enough to keep them from simply scattering anywhere. The liquid sticks to itself, but not so strongly that it has a fixed shape.
As the temperature goes up, molecules in a liquid (as in a solid) move more rapidly. The faster they move, the further they can get from the other molecules, and thus, they take up more space. As with solids, higher temperatures result in most liquids taking up more space, but the volume (as with solids) increase is small by comparison to the volume of the original.
Gases
When in the gas state, matter has neither a definite volume nor a definite shape.
Gases, at any given temperature, change shape and volume to fit and fill the container in which they are kept. Changing the size or shape of the container results in the gas rearranging to fill it.
This is because the molecules in a gas are moving so rapidly that they have exceeded the force that holds solids and liquids together. They have "escaped" and move freely within whatever space they are contained within.
As the temperature continues to go up, they will continue to move more and more rapidly. This change of kinetic energy will affect how hard they crash into the walls of the container—that is, if the volume does not change, as temperature goes up, the pressure in the container will go up.
Plasma
At extremely high temperatures or low pressures, the kinetic energy of the molecules of a gas will be so high the electrons become free.
Plasmas are created when conditions are such that the atoms "shake off" their electrons. The space is filled up with the atom's nuclei and its electrons, but they are not bound to each other. From the framework of the kinetic theory of matter, plasmas exist when the kinetic energy exceeds the force that binds the electrons to the atom. This happens at very high temperatures, very low pressures, or some combination of the two.
Bose-Einstein Condensate
A state of matter where molecular kinetic energy is nearly zero (thus, the molecules are nearly motionless).
When in the Bose-Einstein condensate state, all of the atoms of a substance behave as if they were a single particle. This occurs at near -273 C (0 K).
When you get to a temperature near absolute zero, something special happens. Atoms begin to clump. The whole process happens at temperatures within a few billionths of a degree, so you won't see this at home. When the temperature becomes that low, the atomic parts can't move at all. They lose almost all of their energy.
Since there is no more energy to transfer (as in solids or liquids), all of the atoms have exactly the same levels, like twins. The result of this clumping is the BEC. The group of rubidium atoms sits in the same place, creating a "super atom." There are no longer thousands of separate atoms. They all take on the same qualities and, for our purposes, become one blob.
Viewing states of matter through the lens of the kinetic theory of matter offers a powerful view of how and why solids, liquids, and gases behave as they do. Understanding the way they respond to increasing temperature (which is a measure of increasing kinetic energy) is more clear when understood from the model of moving molecules.
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For additional exposure to the above concepts, check out this video:
In addition to physical properties like hardness, malleability, and melting point, matter has properties related to how they are arranged at the molecular level. Chemical properties can only be observed when a substance interacts with other substances and changes.
Chemical Properties:
any ability to produce change in the composition of matter at the molecular level.
can only be observed when the substances in a sample of matter change into different substances.
A chemical property is any of a material's properties that becomes evident during or after a chemical reaction; that is, any quality that can be established only by changing a substance's chemical identity. Simply speaking, chemical properties cannot be determined just by viewing or touching the substance; the substance's internal structure must be affected greatly for its chemical properties to be investigated. When a substance goes under a chemical reaction, the properties will change drastically, resulting in chemical change. (https://en.wikipedia.org/wiki/Chemical_property)
Two chemical properties are flammability and reactivity.
Flammability
Flammability is a material's ability to burn in the presence of oxygen.
Burning is a chemical reaction in which molecules of the flammable substance combine with oxygen and give off energy that causes the air nearby to glow and give off light (flame).
Reactivity
Reactivity is the property that describes how readily a substance combines chemically with other substances.
Substances react with other substances in different ways. Some things are highly reactive and others are not. Oxygen is an example of something that reacts easily. Nitrogen is an example of something that does not.
Many chemical properties require a more advanced understanding of chemistry, but here are a some of them:
• Toxicity
• Types of chemical bonds that can be formed
• Heat of combustion: how much energy is given of when it burns
• Enthalpy of formation
• Acidity or basicity
• Radioactivity
Chemical Changes
Chemical changes (which rely on chemical properties) occur when one substance reacts with another substance and forms one or more NEW substances that are different in molecular composition compared to the original substances. For example…
Many people know that water is chemically represented by H2O. This notation means that two molecules of hydrogen chemically combine with one molecule of oxygen to make up a molecule of water. So, to form water, two substances, hydrogen and oxygen, chemically react, and the NEW substance is water. Water is different from both the hydrogen and oxygen that form it.
Evidence of Chemical Change
When chemical changes occur, there are usually physical changes and often other signs of the change.
A Change in Color
Many chemical changes result in the new substance showing a different color than the original.
Production of Gas
Some reactions release gas, and can be observed as bubbles or an odor.
Formation of a Precipitate
In liquid mixtures, chemical reactions will often cause the newly formed substances to take on a solid form and suspend more obviously in the liquid. This process is called formation of a precipitate.
The solid that forms in a liquid mixture is called a precipitate. The precipitate may remain suspended in the liquid, may settle to the bottom, or may float to the top.
Temperature Change
It is not uncommon for chemical changes to involve a noticeable temperature change. When a chemical change gives off heat (the system gets warmer), it is said to be exothermic. When a chemical change takes in heat (the system cools off), it is said to be endothermic.
It is not always easy to tell if an observed change is physical or chemical. A heated piece of iron will change color, but still be iron. Gas bubbles will form when water's temperature approaches its boiling point, but it is still water.
For a chemical change to take place, two or more substances must change at the molecular level to become one or more NEW substances.
A physical property is any attribute, quality, or characteristic of a material that can be observed or measured without changing the composition of the substances in the material. There are many different properties that can be observed. The following are some examples.
Viscosity
Viscosity is the tendency of a liquid to keep from flowing—its resistance to flowing.
viscosity
the degree to which something is thick, sticky, and semifluid in consistency, due to internal friction.
a quantity expressing the magnitude of internal friction, as measured by the force per unit area resisting a flow in which parallel layers unit distance apart have unit speed relative to one another.
One way to think about viscosity is to consider how "thick" a liquid is. Syrup is MORE viscous than water is.
The viscosity of a liquid usually decreases as its temperature goes up.
Conductivity
Conductivity is used to express how well a material allows heat or electricity to flow.
conductivity
the degree to which a specified material conducts electricity, calculated as the ratio of the current density in the material to the electric field that causes the flow of current. It is the reciprocal of the resistivity.
(also thermal conductivity)the rate at which heat passes through a specified material, expressed as the amount of heat that flows per unit time through a unit area with a temperature gradient of one degree per unit distance.
Materials that have high conductivity, such as metals, are called conductors.
Malleability
Malleability is the ability of a solid to be hammered without shattering.
malleable
(of a metal or other material) able to be hammered or pressed permanently out of shape without breaking or cracking.
Most metals malleable to a greater degree than are other things, like ice or glass.
Hardness
Hardness of a material relates to the degree to which its surface can be penetrated. For an object to scratch another object, it must be made of a material that has more hardness then the other.
hardness
a measure of how resistant solid matter is to various kinds of permanent shape change when a compressive force is applied.
Melting and Boiling Points
The melting point is the temperature at which a substance changes from solid to liquid. This same temperature is also the point at which the substance changes from a liquid to solid (freezing point).
The boiling point is the temperature at which a substance changes from a liquid to a gas. At this same temperature, gases condense into a liquid (condensation point).
Density
Density is the ratio of a substance's mass to its volume and can be expressed mathematically as D=M/V. Density results from the number of protons, neutrons, and electrons in the atoms that make up the substances and how closely they are arranged to each other either in the substance.
The physical properties of a material can be used to help identify it. A sample can be compared to known quantities to determine if the sample is made from them. For example, if an unknown metal has a density of 10.5 g/cm, it might be silver. If the other properties of the unknown match other known properties of silver, then the conclusion that the sample is sliver might be well-founded.
Separating Mixtures
Some physical properties can be used to separate mixtures. For example, a strong magnet could extract iron shavings from sand.
Other processes can be used with fluids.
Filtration
Filtration is a process that uses a porous material to separate substances based on the size of their molecules.
A sample of the substance is poured through a filter and the filtrate comes out. Large particles of a suspension will be deposited on the filter paper as a residue.
filtrate
a liquid that has passed through a filter
Evaporation
Evaporation is a process that will remove a liquid from a solution leaving behind the solid.
If a solutions is exposed to a temperature that is above the boiling point of the solvent, the solvent will turn to gas and leave the solute behind.
Evaporation is (one example) useful for separating a mixture of a solid and a liquid.
Distillation
Distillation is a process that separates the substances in a solution based on their boiling points.
If a solutions is exposed to a temperature that is above the boiling point of the solvent, the solvent will turn to gas and leave the solute behind.
Distillation can separate a mixture of two liquids that have different boiling points such as alcohol and water.
Centrifugal Separation
A centrifuge can be used to separate a suspension into layers based on the density of the particles. Samples are exposed to strong centrifugal forces which causes the most dense particles to separate from the less dense particles.
Some physical properties can be changed. For example, hardness and viscosity will change when a substance goes from a solid to a liquid. Some changes are reversible. Others are not. Freezing and melting both can be reversed. Scratching or changing the shape (flattening) are not directly reversible.
Everything is made of matter (and energy) of one kind or another. If you can see, smell, taste, or feel it, it is matter.
matter
physical substance in general, as distinct from mind and spirit; (in physics) that which occupies space and possesses rest mass, especially as distinct from energy.
There are two main groupings of matter: pure substances and other substances.
First, we will consider pure substances. Pure substances have the following characteristics:
Matter that has exactly the same composition.
Every sample of a pure substance has the same properties because it has a fixed, uniform composition.
There are two types of pure substances:
Elements
Compounds
Elements:
Element
each of more than one hundred substances that cannot be chemically interconverted or broken down into simpler substances and are primary constituents of matter. Each element is distinguished by its atomic number, i.e., the number of protons in the nuclei of its atoms.
Every sample of an element has the same properties because it has a fixed, uniform composition because an element contains only one type of atom. (An atom is defined by its unique combination of protons, neutrons, and electrons. Protons neutrons, and electrons are the basis for all matter.) No two elements contain the same type of atom.
Key points about elements:
All samples of any element share the same properties.
Elements have a fixed, uniform composition because they contain only one type of atom.
All of the atoms of a given element have a unique combination of protons, neutrons, and electrons.
Compounds:
Compound
a substance formed from two or more elements chemically united in fixed proportions
Every sample of a compound has the same properties because it has a fixed, uniform composition made up of a specific combination of other simpler substances (elements or other compounds) in set, fixed, specific ratios.
The properties of a compound differ from those of the substances from which it is made. For example, water is a liquid at room temperature, but both hydrogen and oxygen are gasses.
Key points about compounds:
All samples of any compound share the same properties.
Compounds have a fix uniform composition because they are made up of a specific combination of other simpler substances in set, fixed, specific ratios. (For instance water is the compound made up when two hydrogen and one oxygen atoms combine.)
The properties of a compound differ from those of the substances from which it is made.
A compound always contains two or more elements joined in a fixed proportion.
Because pure substances are joined and defined at the atomic level you cannot physically separate them into anything other than smaller quantities of the same thing. Any subdivision of an element or a compound will have the same properties as the original, but scaled down for size.
Not all matter is classified as a pure substance.There are other types of substances called mixtures.
Mixtures are made up of various substances, but each substance can be separated because they are not bound at the atomic level. (They are not chemically or atomically bonded.)
One analogy for a mixture is a salad. Though tossed together, each part of the salad retains its individual characteristics and identity. All of the tomatoes could be picked out because they are not bound to the other parts of the salad.
Based on how they are put together, mixtures can be classified as heterogeneous or homogeneous.
Heterogeneous mixtures:
The parts of the mixture are noticeably different from one another.
The composition is not the same throughout.
You CAN divide out different parts…like picking tomatoes out of a salad!
Homogeneous mixtures:
The parts of the mixture are not noticeably different from one another.
The composition is the same throughout.
You CANNOT easily divide out different parts. It’s like salt water.
The substances are so evenly distributed that it is hard to distinguish one substance in the mixture from another.
Another way to classify mixtures is to look at how they behave under certain conditions. This classifying method mostly relates to mixtures involving fluids (liquids and gasses).
Mixtures can be classified as solutions, suspensions, or colloids.
Solutions:
Solution — a liquid mixture in which the minor component (the solute) is uniformly distributed within the major component (the solvent).
SOLVENT: the major component in a solution. The thing that does the dissolving…
SOLUTE: the minor component in a solution. The thing that dissolves…
Key points about solutions:
Homogeneous
SMALL particles of one substance within another substance.
Liquid solutions do not separate into distinct layers.
Cannot be filtered into different parts.
Does not scatter light.
Suspensions:
Suspension — a mixture in which particles are dispersed throughout the bulk of a fluid
Key points about suspensions:
Heterogeneous
LARGER particles of one substance within another substance.
Liquid suspensions do separate into distinct layers.
Can be filtered into different parts.
Will scatter light—suspensions are cloudy.
Colloids:
Colloid — a homogeneous, noncrystalline substance consisting of large molecules or ultramicroscopic particles of one substance dispersed through a second substance. Colloids include gels, sols, and emulsions; the particles do not settle and cannot be separated out by ordinary filtering or centrifuging like those in a suspension.
gel: a semisolid colloidal suspension of a solid dispersed in a liquid.
sol: a fluid suspension of a colloidal solid in a liquid
emulsion: a fine dispersion of minute droplets of one liquid in another in which it is not soluble or miscible.
Key points about colloids:
Homogeneous
INTERMEDIATE sized particles of one substance within another substance.
Liquid colloids do not separate into distinct layers.
Cannot be filtered into different parts.
Will scatter light—like fog or milk.
What if? Milk (a colloid) has salt dissolved into it? — The saltiness would act like a solution. Now, mix dirt into the salty milk? — Now, there is a suspension of dirt in the salty milk!
Conclusion:
The physical universe is composed of matter, and matter can be classified into different types. Understanding what they are, how they are alike, and how they are different is a fundamental part of viewing the universe through the lens of science.
