Properties of Matter Investigation 3

Focus Questions How do shape, volume, and particle motion help classify solids, liquids, and gases? How do shape, volume, and particle motion help classify solids, liquids, and gases? What are solids, liquids, and gases? What are solids, liquids, and gases? What is viscosity? What is viscosity?

Solids, Liquids, and Gases Your world is full of substances that can be classified as solids, liquids, and gases. Your world is full of substances that can be classified as solids, liquids, and gases. Those substances may be elements, compounds, or mixtures. Those substances may be elements, compounds, or mixtures. To define solids, liquids, and gases, you need to examine their properties. To define solids, liquids, and gases, you need to examine their properties. The states of matter are defined not by what they are made of, but mainly by whether or not they hold their volume and shape. The states of matter are defined not by what they are made of, but mainly by whether or not they hold their volume and shape.

Solids If you were to pick up a solid object, such as a pen, would the pen ever change it size or shape as you moved it? If you were to pick up a solid object, such as a pen, would the pen ever change it size or shape as you moved it? Of course not! A solid has a definite volume and a definite shape. Of course not! A solid has a definite volume and a definite shape. If your pen has a volume of 6cm 3 and a cylindrical shape, then it will keep that volume and shape in any position and in any container. If your pen has a volume of 6cm 3 and a cylindrical shape, then it will keep that volume and shape in any position and in any container.

Particles in a Solid The particles that make up a solid are packed very closely together. The particles that make up a solid are packed very closely together. In addition, each particle is tightly fixed in one position. In addition, each particle is tightly fixed in one position. This makes it hard to separate them. This makes it hard to separate them. Because the particles in a solid are packed tightly together and stay in fixed positions, a solid has a definite shape and volume. Because the particles in a solid are packed tightly together and stay in fixed positions, a solid has a definite shape and volume.

Particles in a Solid cont. Are the particles in a solid completely motionless? Are the particles in a solid completely motionless? No, these particles vibrate, meaning they move back an forth slightly. No, these particles vibrate, meaning they move back an forth slightly. This motion is similar to a person running in place. This motion is similar to a person running in place.

Types of Solids In many solids, the particles form a regular, repeating pattern. In many solids, the particles form a regular, repeating pattern. These patterns create crystals. These patterns create crystals. Solids that are made up of crystals are called crystalline solids. Solids that are made up of crystals are called crystalline solids. Salt, sugar, sand, and snow are examples of crystalline solids. Salt, sugar, sand, and snow are examples of crystalline solids. When a crystalline solid such as snow is heated, it melts at a distinct temperature called its melting point. When a crystalline solid such as snow is heated, it melts at a distinct temperature called its melting point.

Types of Solids cont. In other solids the particles are not arranged in a regular pattern. In other solids the particles are not arranged in a regular pattern. These solids are called amorphous solids. These solids are called amorphous solids. Plastics, rubber, and glass are amorphous solids. Plastics, rubber, and glass are amorphous solids. Unlike a crystalline solid, an amorphous solid does not have a distinct melting point. Unlike a crystalline solid, an amorphous solid does not have a distinct melting point. Instead, when it is heated it becomes softer and softer as temperature rises. Instead, when it is heated it becomes softer and softer as temperature rises.

Liquids Unlike a solid, a liquid has no shape of its own. Instead, a liquid takes on the shape of its container. Without a container, a liquid spreads into a wide, shallow puddle.

Liquids cont. However, liquids are like solids in that they do not easily compress or expand. However, liquids are like solids in that they do not easily compress or expand. If you tried to squeeze a water filled plastic bag, for example, the water might change its shape, but its volume would not decrease or increase. If you tried to squeeze a water filled plastic bag, for example, the water might change its shape, but its volume would not decrease or increase. Water has the same volume no matter what shape its container has. Water has the same volume no matter what shape its container has.

Particles in a Liquid The particles in a liquid are packed almost as closely as in a solid. The particles in a liquid are packed almost as closely as in a solid. However, the particles in a liquid move around one another freely. However, the particles in a liquid move around one another freely. Because its particles are free to move, a liquid has no definite shape. However, it does have a definite volume. Because its particles are free to move, a liquid has no definite shape. However, it does have a definite volume.

Viscosity Because particles in a liquid are free to move around one another, a liquid can flow from place to place. Because particles in a liquid are free to move around one another, a liquid can flow from place to place. For this reason, a liquid is also called a fluid, meaning “a substance that flows.” For this reason, a liquid is also called a fluid, meaning “a substance that flows.” Some liquids flow more easily than others. Some liquids flow more easily than others. The resistance of a liquid to flowing is called viscosity. The resistance of a liquid to flowing is called viscosity.

Viscosity cont. Liquids with a high viscosity flow slowly. Liquids with a high viscosity flow slowly. Cold molasses is an example of a liquid with particularly high viscosity. Cold molasses is an example of a liquid with particularly high viscosity. Liquid with a low viscosity flow quickly. Liquid with a low viscosity flow quickly. Water and vinegar have relatively low viscosities. Water and vinegar have relatively low viscosities.

Viscosity cont. The viscosity of lava that erupts from a volcano helps classify the type of volcanic eruption. The viscosity of lava that erupts from a volcano helps classify the type of volcanic eruption. A volcano erupts quietly if it has thin, runny lava— that is lava with low viscosity. A volcano erupts quietly if it has thin, runny lava— that is lava with low viscosity. High-viscosity lava, which is thick and sticky, is typical of a volcano that erupts explosively. High-viscosity lava, which is thick and sticky, is typical of a volcano that erupts explosively.

Gases Unlike solids and liquids, a gas can change volume very easily. Unlike solids and liquids, a gas can change volume very easily. If you put a gas in a container with a top, the gas particles will spread apart or squeeze together to fill the container. If you put a gas in a container with a top, the gas particles will spread apart or squeeze together to fill the container. The volume and shape of a gas is the volume and shape of its container. The volume and shape of a gas is the volume and shape of its container.

Gases cont. Example: Take a deep breath. Example: Take a deep breath. Your chest expands. Can you feel the air coming through your nose and mouth? Your chest expands. Can you feel the air coming through your nose and mouth? Air is a mixture of gases that acts as one gas. Air is a mixture of gases that acts as one gas. When you breathe in, air moves from your mouth to your windpipe to your lungs. When you breathe in, air moves from your mouth to your windpipe to your lungs. In each place, the air changes shape and volume. In each place, the air changes shape and volume.

Gases cont. If you could see the individual particles that make up a gas, you would see tiny particles flying at high speeds in all directions. If you could see the individual particles that make up a gas, you would see tiny particles flying at high speeds in all directions. Gas particles spread apart, filling all the space available to them. Thus a gas has neither definite shape nor volume. Gas particles spread apart, filling all the space available to them. Thus a gas has neither definite shape nor volume.

Review Describe properties you would use to classify a substance as a solid. Describe properties you would use to classify a substance as a solid. How does the movement of particles in a liquid help to explain the shape and volume of liquids? How does the movement of particles in a liquid help to explain the shape and volume of liquids? Use what you know about the particles in a gas to explain why a gas has no definite shape and no definite volume. Use what you know about the particles in a gas to explain why a gas has no definite shape and no definite volume.