Chapter 3 Matter and Energy

Matter

anything that occupies space and has mass

ex: steel, water, wood, plastic, air, microscopic dust

atoms

submicroscopic particles that are the fundamental building blocks of matter

molecules

two or more atoms joined to one another in specific geometric arrangements

states of matter

solid, liquid, and gas

States of Water

ice (solid), water (liquid), and steam (gas)

Solid

atoms or molecules pack close to each other in fixed locations

vibrate or oscillate, but they do not move around each other

definite shape

definite volume

incompressible

ex: Ice, diamond, quartz, and iron

Crystalline solid

Atoms or molecules are arranged in geometric patterns with long-range, repeating order

ex: salt and diamond

Amorphous solid

Atoms or molecules do not have long-range order

ex: glass, rubber, and plastic

Liquid

atoms or molecules are close to each other but are free to move around and by each other

fixed volume because their atoms or molecules are in close contact

indefinite shape

definite volume

incompressable

assume the shape of their containers because the atoms or molecules are free to move relative to one another

ex: Water, gasoline, alcohol, and mercury

Gas

atoms or molecules are separated by large distances and are free to move relative to one another

compressible because atoms or molecules that compose gases are not in contact with one another

indefinite shape

indefinite volume

compressible

always assume the shape and volume of their containers

ex: Oxygen, helium, and carbon dioxide

pure substance

composed of only one type of atom or molecule

mixture

composed of two or more different types of atoms or molecules combined in variable proportions

Element

A pure substance that cannot be broken down into simpler substances

No chemical transformation can decompose an element into simpler substances.

All known elements are listed in the periodic table.

A periodic table can be found on the inside front cover of this book, and the elements are listed in alphabetical order on the inside back cover of this book.

Helium

A pure substance composed of only one type of atom—helium atoms

Compound

A pure substance composed of two or more elements in fixed definite proportions

Compounds are more common than pure elements.

Most elements are chemically reactive and combine with other elements to form compounds.

Water, table salt, and sugar are examples of compounds.

Compounds can be decomposed into simpler substances.

Water

A pure substance composed only of water molecules

Two elements in fixed, definite proportions

compound

a pure substance composed of different atoms that are chemically united (bonded) in fixed definite proportions

mixture

composed of different substances that are not chemically united but simply mixed together

physical property

a substance displays change in its appearance without changing its composition

ex: odor

chemical property

a substance displays only through changing its composition

ex: flammability

State changes

transformations from one state of matter to another, such as from solid to liquid—are always physical changes

reactants

the substances present before the chemical change

products

substances present after the change

Law of Conservation of Mass

There is no new matter.

Matter is neither created nor destroyed in a chemical reaction, only changed in form

In a nuclear reaction, significant changes in mass can occur.

In chemical reactions, however, the changes in mass are so minute that they can be ignored.

During physical and chemical changes, the total amount of matter remains constant.

Energy

the capacity to do work

Work

the result of a force acting on a distance; driven by energy

Law of Conservation of Energy

energy is neither created nor destroyed

• The total amount of energy is constant.

• Energy can be changed from one form to another.

• Energy can be transferred from one object to another.

• Energy cannot be created out of nothing, and it does not vanish into nothing.

kinetic energy

energy associated with its motion

potential energy

the energy associated with its position or composition

Electrical energy

The energy associated with the flow of electrical charge

Thermal energy

The energy associated with the random motions of atoms and molecules in matter

measured by temperature

atoms and molecules that compose matter are in constant random motion

the hotter an object —>greater random motion —>higher temp.

Chemical energy

A form of potential energy associated with the positions of the particles that compose a chemical system in bonds

joule (J)

unit of energy

calorie (cal)

the amount of energy required to raise the temperature of 1 g of water by 1 °C

Calorie (Cal)

nutritional; equivalent to 1000 little c calories

1 cal = 4.184 J

calorie to joules

1 Cal = 1000 cal

Calorie to calories

exothermic reaction

energy is released

endothermic reaction

energy is absorbed

Heat

the transfer or exchange of thermal energy caused by a temperature difference

ex: when a piece of cold ice is dropped into a cup of warm water, heat (thermal energy) is transferred from the water to the ice

Temperature

a measure of the thermal energy of matter

K = °C + 273.15

Kelvin to Celsius

°C = °F-32/1.8

Celsius to Fahrenheit

Heat capacity

The quantity of heat (usually in joules) required to change the temperature of a given amount of the substance by 1 °C

specific heat capacity

When the amount of the substance is expressed in grams, the heat capacity is called

J/g °C

4.184 J/g °C

Water Heat Capacity

Energy Temperature Change and Heat Capacity Equation

q = m x C x ΔT

q

the amount of heat in joules

m

the mass of the substance in grams

C

the specific heat capacity in J/g °C

T

the temperature change in Celsius

Homogenous mixture

Having the same composition throughout

Heterogeneous mixture

Having a composition that varies from region to region

Physical change

the appearance of matter may change, but its composition does not

ex: ice to liquid water (still water molecules)

chemical change

the composition of matter changes

ex: copper turning green due to formation of new compounds, rust (oxidize)