States and Physical Changes of Matter
Lesson Objectives
Identify the four states of matter
Identify the evidence of physical changes in matter
Introduction
The four fundamental states of matter. Clockwise from top left, they are solid, liquid, plasma and gas, represented by an ice sculpture, a drop of water, electrical arcing from a tesla coil, and the air around clouds respectively.
Guided Learning
Four States of Matter
How do solids, liquids, and gases differ? Their physical properties are compared in the figure below and described below.
Solids
Ice is an example of solid matter. A solid is matter that has a fixed volume and a fixed shape. The figure below shows examples of matter that are usually solids under Earth conditions. In the figure, salt and cellulose are examples of crystalline solids. The particles of crystalline solids are arranged in a regular repeating pattern. The steaks and candle wax are examples of amorphous ("shapeless") solids. Their particles have no definite pattern.
The volume and shape of a solid can be changed, but only with outside help. How could you change the volume and shape of each of the solids in the figure without changing the solid in any other way?
Liquids
Ocean water is an example of a liquid. A liquid is matter that has a fixed volume but not a fixed shape. Instead, a liquid takes the shape of its container. If the volume of a liquid is less than the volume of its container, the top surface will be exposed to the air, like the oil in the bottles in the figure below.
Each bottle contains the same volume of oil. How would you describe the shape of the oil in each bottle?
Gases
Water vapor is an example of a gas. A gas is matter that has neither a fixed volume nor a fixed shape. Instead, a gas takes both the volume and the shape of its container. It spreads out to take up all available space. You can see an example in figure.
When you add air to a bicycle tire, you add it only through one tiny opening. But the air immediately spreads out to fill the whole tire.
Plasmas
You’re probably less familiar with plasmas than with solids, liquids, and gases. Yet, most of the universe consists of plasma. Plasma is a state of matter that resembles a gas but has certain properties that a gas does not have. Like a gas, plasma lacks a fixed volume and shape. Unlike a gas, plasma can conduct electricity and respond to magnetism. That’s because plasma contains charged particles called ions. This gives plasma other interesting properties. For example, it glows with light.
Where can you find plasmas? Two examples are shown in the figure below. The sun and other stars consist of plasma. Plasmas are also found naturally in lightning and the polar auroras (northern and southern lights). Artificial plasmas are found in fluorescent lights, plasma TV screens, and plasma balls like the one that opened this chapter. Learn more about Plasmas with this three-minute video.
Both the northern lights (aurora borealis) and a plasma TV contain matter in the plasma state. What other plasmas are shown in the northern lights picture?
These stunning rock arches in Utah were carved by wind-blown sand. Repeated scouring by the sand wore away the rock, bit by tiny bit, like sandpaper on wood. The bits of rock worn away by the sand still contain the same minerals as they did when they were part of the large rock. They have not changed chemically in any way. Only the size and shape of the rock have changed, from a single large rock to millions of tiny bits of rock. Changes in size and shape are physical changes in matter.
What Is a Physical Change?
A physical change is a change in one or more physical properties of matter without any change in chemical properties. In other words, matter doesn’t change into a different substance in a physical change. Examples of physical change include changes in the size or shape of matter. Changes of state—for example, from solid to liquid or from liquid to gas—are also physical changes. Some of the processes that cause physical changes include cutting, bending, dissolving, freezing, boiling, and melting. Four examples of physical change are pictured below.
Watch this video about physical changes. Then answer the questions below.
Describe an example of temperature causing a change in the size of matter.
How is temperature related to changes in the state of matter?
Q: In the figure below, what physical changes are occurring?
A: The paper is being cut into smaller pieces, which is changing its size and shape.
The ice cubes are turning into a puddle of liquid water because they are melting.
The lighthouse is becoming coated with ice as ocean spray freezes on its surface. This is another change of state.
Reversing Physical Changes
When matter undergoes physical change, it doesn’t become a different substance. Therefore, physical changes are often easy to reverse. For example, when liquid water freezes to form ice, it can be changed back to liquid water by heating and melting the ice.
Q: Sugar dissolving in water is a physical change. How could this change be reversed?
A: The sugar water could be boiled until the water evaporates, leaving behind the sugar. Water vapor from the boiling water could be captured and cooled. The water vapor would condense and change back to liquid water.
Review
A solid is matter that has a fixed volume and a fixed shape.
A liquid is matter that has a fixed volume but not a fixed shape.
A gas is matter that has neither a fixed volume nor a fixed shape.
Like a gas, plasma lacks a fixed volume and shape. Unlike a gas, it can conduct electricity and respond to magnetism.
A physical change in matter is a change in one or more of matter’s physical properties. In a physical change, matter may change its size, shape, or state, but its chemical properties do not change.
Because the chemical properties of matter remain the same in a physical change, a physical change is often easy to reverse.
Gas
Gas is matter that has neither a fixed volume nor a fixed shape.
Liquid
Liquid is matter that has a fixed volume but not a fixed shape.
Solid
Solid is matter that has a fixed volume and a fixed shape.
Physical Property
A physical property is a property of matter that can be measured or observed without matter changing to an entirely different substance (melting point, boiling point, odor, density, hardness, luster, freezing point, malleability, conductivity).
Physical Change
A physical change is a change in one or more of a matter’s physical properties.
Plasma
Plasma is a state of matter that lacks a fixed volume and shape, but can conduct electricity and respond to magnetism.
Original document from CK-12 for non commercial use. MnLC and MDCC