chemistry 110- Exam 1

Examples of chemistry in everyday life

Digesting food; synthesizing polymers for clothing, cookware, and credit cards; refining crude oil into gasoline and other products

Chemistry is based on…

Observation, and experimentation

Hypothesis

Tentative explanation of observations

Law of science

Summarize a vast number of experimental observations, and describe or predict some facet of the natural world

Theory

A well sustained, comprehensive, testable explanation of a particular aspect of nature.

Matter

Anything that occupies space and has mass

Three most common states or phases of matter

1. A solid is rigid and possesses a definite shape

2. A liquid flows and takes the shape of its container

3. A gas takes both the shape and volume of its container

Mass

is a measure of the amount of matter in an object

Weight

refers to the force that gravity exerts on an object

The objects mass is the same on the earth and the moon but its weight is different

True

Element

Type of pure substance that cannot be broken down into simpler substances by chemical changes

Elements- facts

1. there are more than 100 known elements

2. ninety of these occur naturally

3. two dozen or so have been created in laboratories

Pure substances and Mixtures pt 1

Pure substances have constant composition

Elements: pure substance that cannot be broken down into simpler substances by chemical changes.

• consists of one type of element

• Examples: Gold (Au), Phosphorus (P), Oxygen (o)

Compounds: pure substances that can be broken down into simpler substances by chemical changes

• Consists of two or more types of elements chemically bonded

• examples: H20, C6H12O6, AgCI

• The properties of compounds are different from the uncombined elements making up the compound

Pure substances and Mixtures pt 2

• A mixture is composed of two or more types of matter that can be present in varying amounts and can be separated by physical changes

• Evaporation is an example of a physical change

• There are two or more types of mixtures: homogenous mixtures and heterogenous mixtures.

Homogenous mixture / solution

exhibits a uniform composition and appears visually the same throughout ex: Salt and water

Heterogenous mixture

has a composition that varies from point to point

atom

the smallest particle of an element that has the properties of that element and can enter into a chemical combination

• Idea first proposed by greek philosophers, leucippus and democritus, in the 5th century BCE.

• 19th century, john dalton of england supported this hypothesis with quantitative measurements

Molecule

Consists of two or more atoms connected by strong forces known as chemical bonds

• the elements hydrogen, oxygen, phosphorus, and sulfur form molecules consisting of two or more atoms of the same element

• The compounds water, carbon dioxide, and glucose consist of combinations of atoms of different elements

properties

The characteristics that enable us to distinguish one substance from another are called properties

Physical property

a characteristic of matter that is not associated with a change in its chemical composition

ex:density, color hardness, melting and boiling points, and electrical conductivity

physical change

a change in the state or properties of matter without any accompanying in its composition

ex: butter into liquid

Chemical property

The change of one type of matter into another type (or the inability to change)is a chemical property

ex: flammability, toxic, acidity, reactivity, and heat of combustion

Extensive property

• depends on the amount of matter present

• ex: mass, volume, heat

Intensive property

• Does not depend on the amount of matter present

• examples: density, temperature

Periodic table

Shows how elements may be grouped according to certain similar properties. the background color denotes whether an element is a metal. metalloid, or nonmetal, whereas the element symbols color indicates whether it is a solid, liquid, or gas.

Measurements

provide the information that is the basis of most of the hypotheses, theories, and laws in chemistry

measurement provides three kinds of information

1. the size or magnitude of the measurement: a number

2. a standard of comparison for the measurement: a unit

3. An indication of the uncertainty of the measurement an estimate of the reliability of the measurement.

volume

the measure of the amount of space occupied by an object