Unit 2: Elementary Physical, Chemical and Thermodynamic Principles Flashcards
What is a Pure Substance?
A pure substance is a form of matter that has a constant composition and properties that are constant throughout the sample.
Elements
Are pure substances that cannot be chemically decomposed into simpler atoms. They are represented on the periodic table of elements
What are Compounds?
Is a pure substance that is made up of two or more elements that are chemically bound to one another in fixed proportions.
Mixtures
Most natural substances in the world are mixtures; that is they are combinations of two or more pure substances that are not chemically bound together. The components of a mixture can therefore be separated by physical means such as screening or distillation.
Homogenous Mixtures
A homogeneous mixture is a mixture in which the components that make up the mixture are uniformly distributed throughout the mixture. The composition of the mixture is the same throughout. There is only one phase of matter observed in a homogeneous mixture at a time. So, you wouldn’t observe both a liquid and a gas or a liquid and a solid in a homogeneous mixture.
Homogeneous Mixture Examples
There are several examples of homogeneous mixtures encountered in everyday life:
Air Sugar water Rainwater Vodka Vinegar Dishwashing detergent Steel
Heterogeneous Mixture
A heterogeneous mixture is a mixture in which the components of the mixture are not uniform or have localized regions with different properties. Different samples from the mixture are not identical to each other. Heterogeneous mixtures are more common than homogeneous mixtures. There are always two or more phases in a heterogeneous mixture, where you can identify a region with properties that are distinct from those of another region, even if they are the same state of matter (e.g., liquid, solid).
Heterogeneous Mixture Examples
Cereal in milk Vegetable soup Pizza Blood Gravel Ice in soda Salad dressing Mixed nuts Bowl of colored candies Soil
Chemical Properties
Chemical Properties are only observed when there is a chemical change or reaction that occurs.
Such as
Heat of Combustion
Toxicity
Flammability
Physical Properties
Are those characteristics used to describe a substance or properties that can be observed without a change in the composition of the matter. They include color, hardness, density, the boiling point.
Solids
Have an ordered Arrangement of atoms or ions close together, giving them a solid structure with a definite shape and volume. They have very little capability to compress or expand.
Liquids
Have a definite volume but no specific shape. Their molecules are close together but are not bound into the rigidity of a solid. They will flow around one another and conform to the shape of their container.
Gases
Have no fixed volume or shape because their molecules are in constant motion. They assume the shape of their container. A gas consists mostly of empty space with the gas molecules far apart from one another.
Atoms
Atoms are the simplest structures of the world. They are comprised of protons (+), neutrons (Neutral), and Electrons (-).
Chemical Reactions
Occurs when atoms come together to form new molecules. This means that bonds between atoms are broken and new ones are formed. The substances that form due to the chemical reaction are called products. At its core chemical reactions involve the interactions of electrons between different atoms. They do not involve reactions within the nucleus. Instead most occur between electrons in the outer orbital or valance shell. These electrons are either removed, added or shared between two or more different atoms.
Evaporation?
Liquid to a Gas
State Change or Physical Change (Change in physical properties without a change in chemical composition.)
Condensation
Gas to a Liquid
State Change or Physical Change (Change in physical properties without a change in chemical composition.)