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Properties of Matter

I. Matter

A. Matter—anything that takes up space and has mass; matter is composed of tiny particles.

1. Three usual states of matter are solid, liquid, and gas.

2. Plasma, a fourth state, occurs only at very high temperatures and is not common on Earth.

B. Solids—have definite shape and volume because particles are packed closely together and merely vibrate in place.

1. Solids in which particles are arranged in a repeating, three-dimensional pattern are called crystals or crystalline solids.

2. Amorphous solids have a random arrangement of particles.

C. Matter with a definite volume but no definite shape is a liquid; a liquid’s particles move more freely than those of a solid.

1. Viscosity is a liquid’s resistance to flow and increases when particles are more strongly attracted to each other.

2. Surface tension—uneven forces acting on the particles of a liquid’s surface.

D. Gas—matter that does not have a definite shape or volume; gas particles spread out evenly as far apart as possible.

II. Changes of State

A. Particles are in constant motion; amount of movement depends on their kinetic energy.

1. Thermal energy—total energy of all the particles in a sample of matter

2. The average kinetic energy of particles in a substance is its temperature.

3. Heat—movement of thermal energy from a substance with a higher temperature to one with a lower temperature

B. Specific heat—amount of heat needed to raise the temperature of 1 g of a substance 1°C

C. Matter can change states as energy is absorbed or released.

1. A change from the solid to the liquid state is called melting.

2. A change from the liquid to the solid state is called freezing.

D. Changes between liquid and gas states

1. A change from liquid to gas is called vaporization.

a. Boiling is vaporization which occurs below the liquid’s surface at its boiling point.

b. Evaporation is vaporization which occurs at the surface of a liquid; molecules must be at or near the surface at the right speed to evaporate.

2. Condensation—a change from gas to liquid

E. Changes between solid and gas states—During sublimation the surface particles of a solid gain enough energy to become a gas.

III. Behavior of Fluids

A. Pressure equals the force exerted on a surface divided by the total area over which the force is exerted or, P = F / A.

1. If force increases over an area, the pressure increases; if force over an area decreases, the pressure decreases.

2. Atmospheric pressure—air presses down on Earth with force.

3. Pressure can be balanced as the pressure pushing down equals the pressure pushing up.

4. As altitude increases, air pressure decreases.

B. Gas pressure in a closed container changes with volume and temperature changes.

1. Decreasing volume increases pressure; increasing volume decreases pressure.

2. Increasing temperature increases pressure; decreasing temperature decreases pressure.

C. Buoyant force—an upward force on an object immersed in a fluid

1. Archimedes’ principle—Buoyant force on an object is equal to the weight of the fluid displaced by the object.

2. Density is mass divided by volume.

a. An object will float in a fluid that is denser than the object.

b. An object with the same density as the fluid will stay at the same level in the fluid.

c. An object will sink in a fluid that is less dense that the object.

D. Pascal’s principle—When a force is applied to a confined fluid, an increase in pressure is transmitted equally to all parts of the fluid.

1. Hydraulic systems allow people to lift heavy objects with relatively little force.

2. When squeezed, liquids will be pushed out of a force pump, a closed container with a hole in it.

IV. Physical Properties

A. Physical property—any characteristic of matter that can be observed without changing the identity of the material

1. Physical properties include color, shape, smell, taste, mass, volume, and density.

2. Density—amount of mass in a given volume; a golf ball would have greater density than a table-tennis ball; the formula for density is: density (g/cm3) = mass(g)/volume (cm3)

3. Density can be used to identify unknown substances; a person could determine the composition of a piece of jewelry by comparing its density with the density of a known substance such as silver or gold.

4. State of matter—whether a substance is a solid, liquid, or a gas at a particular temperature and pressure

5. Some physical properties are size-dependent (length, width, height, volume, and mass) while others are size-independent (density, color, state).

B. Matter can be classified as an acid or a base.

1. Acids tend to have a sharp smell and a sour taste (but you should NEVER taste anything in a laboratory) with a pH between 0 and 7; citrus fruits contain acids.

2. Bases feel slippery and taste bitter and have a pH of between 7 and 14; a bar of soap is a base.

3. Water, with a pH of exactly 7, is neither an acid nor a base; it is neutral.

V. Chemical Properties

A. Chemical property—characteristic of something that allows it to change to something new

1. Chemical properties include flammability, toxicity, and reactivity with oxygen; when a half-eaten apple turns brown in the air, a chemical reaction with oxygen has occurred.

2. Silver and gold have lower reactivity than many other metals, which helps make them good choices for jewelry.

3. Chlorine compounds change the chemical properties of pool water, making it more acidic in order to eliminate algae, bacteria, and insects.

a. Standing water, without added chlorine, can become a breeding ground for insects, such as mosquitoes.

b. Plants, algae, and bacteria can make a pool unfit for swimming.

c. The more acidic chlorinated pool water can also irritate the skin and eyes of swimmers.

B. Acids and bases have chemical properties that make them both useful and harmful.

1. Many acids react with, or corrode, certain metals and can harm living organisms.

a. Tomato sauce is acidic enough to react with aluminum foil, but will not harm human beings.

b. Acid rain can damage plant and animal tissues.

c. Sulphuric acid is useful in industry, but causes burns on skin.

2. Strong bases can damage living tissue; ammonia fumes can cause nosebleeds in some people.

3. Salts—compounds made of a metal and nonmetal and that are formed when acids and bases react

a. Table salt can be formed from a base sodium hydroxide and hydrochloric acid.

b. Calcium carbonate, or chalk, and ammonium chloride, which is used in batteries, are useful salts.

VI. Physical and Chemical Changes

A. Physical change—any change in size, shape, form, or state where the identity of the matter stays the same

1. Cutting a watermelon into slices is an example of a physical change.

2. Change of state is a common physical change.

a. Solid to liquid (ice melting)

b. Liquid to solid (water freezing)

c. Liquid to gas (water boiling and creating steam)

d. Gas to liquid (water vapor condensing into water such as when dew forms)

B. Chemical change—one material changes into a different material with different properties or characteristics

1. Examples of chemical changes include digestion, photosynthesis, paint drying, and oil burning.

2. In a chemical change, new materials are formed that are different from the starting materials.

3. A chemical change cannot easily be reversed.

4. Signs of chemical changes include the release or absorption of energy in the form of light, heat, or sound; formation of a gas or solid, not from a change of state, can indicate a chemical change.

C. Leaves changing color indicates a chemical change in nature.

1.Weathering of Earth’s surface is a physical change that takes place over long time periods.

2. Chemical weathering can create cave formations.

3. Acid rain is a form of unnatural chemical change.