Chapter 3.1-3.3

Pure Substance

is matter that has a fixed or definite composition. There are two kinds of pure substances: elements and compounds

element

An element, the simplest type of a pure substance, is composed of only one type of material such as silver, iron, or aluminum. Every element is composed of atoms, which are extremely tiny particles that make up each type of matter. Silver is composed of silver atoms, iron of iron atoms, and aluminum of aluminum atoms.

compound

is also a pure substance, but it consists of atoms of two or more elements always chemically combined in the same proportion.

For example, in the compound water, there are two hydrogen atoms for every one oxygen atom, which is represented by the formula H2O.

how can pure substances be broken down?

Pure substances that are compounds can be broken down by chemical processes into their elements. They cannot be broken down through physical methods such as boiling or sifting.

Mixtures

two or more different substances are physically mixed, but not chemically combined. Much of the matter in our everyday lives consists of mixtures. The air we breathe is a mixture of mostly oxygen and nitrogen gases

Unlike compounds, the proportions of substances in a mixture are not consistent but can vary

How can be mixtures be broken down?

Physical processes can be used to separate mixtures because there are no chemical interactions between the components.

homoegenous mixture

n a homogeneous mixture, also called a solution, the composition is uniform throughout the sample. We cannot see the individual components, which appear as one state. Familiar examples of homogeneous mixtures are air

heterogenous mixture

the components do not have a uniform composition throughout the sample. The components appear as two separate regions. For example, a mixture of oil and water is heterogeneous because the oil floats on the surface of the water. Other examples of heterogeneous mixtures are a cookie with raisins and orange juice with pulp.

How to separate mixtures?

Solids are separated from liquids by filtration, which involves pouring a mixture through a filter paper, set in a funnel. The solid (residue) remains in the filter paper, and the filtered liquid (filtrate) moves through. In chromatography, different components of a liquid mixture separate as they move at different rates up the surface of a piece of chromatography paper

What are the states of matter?

solids, liquids, and gases

Solid

definite shape and volume.

Has a definite volume

very close particles

particle vibrate slowly

very strong attraction attraction between particles

Liquid

has a definite volume, but not a definite shape. In a liquid, the particles move in random directions but are sufficiently attracted to each other to maintain a definite volume, although not a rigid structure. Thus, when water, oil, or vinegar is poured from one container to another, the liquid maintains its own volume but takes the shape of the new container.

Gas

does not have a definite shape or volume. In a gas, the particles are far apart, have little attraction to each other, and move at high speeds, taking the shape and volume of their container. When you inflate a bicycle tire, the air, which is a gas, fills the entire volume of the tire. The propane gas in a tank fills the entire volume of the tank.

Physical Properties

are those characteristics that can be observed or measured without affecting the identity of a substance. In chemistry, typical physical properties include the shape, color, melting point, boiling point, and physical state of a substance

Physical Change

its state, size, or appearance will change, but its composition remains the same.

Chemical Properties

describe the ability of a substance to change into a new substance.

chemical change

Takes place, the original substance is converted into one or more new substances, which have new physical and chemical properties. For example, the rusting or corrosion of a metal, such as iron, is a chemical property. In the rain, an iron (Fe) nail undergoes a chemical change when it reacts with oxygen O2 to form rust Fe2O3.

Examples of Physical Changes:

Water boils to form water vapor.
Copper is drawn into thin copper wires.
Sugar dissolves in water to form a solution.
Paper is cut into tiny pieces of confetti.

Example of Chemical Changes:

	Shiny, silver metal reacts in air to give a black, grainy coating.
	A piece of wood burns with a bright flame and produces heat, ashes, carbon dioxide, and water vapor.
	Heating sugar forms a smooth, caramel-colored substance.
	Iron, which is gray and shiny, combines with oxygen to form orange-red rust.

Identify the physical changes in the following:
a. Water freezes on a pond.
b. Gas bubbles form when baking powder is placed in vinegar.
c. A log is cut for firewood.
d. Butter melts in a warm room.

Water freezes on a pond, c. a log is cut for firewood, and d. butter melts in a warm room are physical changes.

Celcius Scale

there are 100 degrees Celsius between the freezing and boiling points of water,

Fahrenheit Scale

has 180 degrees Fahrenheit between the freezing and boiling points of water.

Connection between Fahrenheit and Celcius Scale

1°C=1.8°F

Kelvin Scale

coldest temperature possible is −273°C (more precisely, −273.15°C). On the Kelvin scale, this temperature, called absolute zero

he Kelvin scale has no negative temperature values. Between the freezing point of water, 273 K, and the boiling point, 373 K, there are 100 kelvins, which makes a kelvin equal in size to a degree Celsius

1K=1C

Classify each of the following as an element, a compound, or a mixture: (3.1)

1. carbon in pencils

2. carbon monoxide (CO) in automobile exhaust

3. orange juice

3.71

• element

• compound

• mixture

Classify each of the following mixtures as homogeneous or heterogeneous: (3.1)

1. hot fudge sundae

2. herbal tea

3. vegetable oil

3.73

• heterogeneous

• homogeneous

• homogeneous

dentify each of the following as a physical or chemical property: (3.2)

1. Gold is shiny.

2. Gold melts at 1064 °C.

3. Gold is a good conductor of electricity.

4. When gold reacts with sulfur, a black sulfide compound forms.

3.77

• physical

• physical

• physical

• chemical

Identify each of the following as a physical or chemical change: (3.2)

1. A plant grows a new leaf.

2. Chocolate is melted for a dessert.

3. Wood is chopped for the fireplace.

4. Wood burns in a woodstove

• chemical

• physical

• physical

• chemical

Calculate each of the following temperatures in degrees Celsius and kelvins: (3.3)

1. The highest recorded temperature in the continental United States was 134 °F in Death Valley, California, on July 10, 1913.

2. The lowest recorded temperature in the continental United States was −69.7°F in Rodgers Pass, Montana, on January 20, 195

3.81

1. 56.7 °C, 330. K

2. −56.5 °C, 217 K