Download Matter

CHEM ESSENTIAL CONCEPTS: THE PUZZLE OF MATTER.
Obj 1.1 Define Chemistry and Matter, and explain the law of conservation of mass
 Chemistry is the science that investigates and explains the structure and properties of matter.
 Matter is anything that has volume (takes up space) and mass (a measure of amount or
quantity). Matter can also be defined as anything that exhibits inertia (a resistance to change
in motion). Examples of matter are all the solids, liquids, gases that make up the stuff of our
world.
 Law of conservation of mass (or matter): Matter can change form, but is neither created nor
destroyed .
Obj 1.2 Classify matter according to its composition
Obj 1.3 Distinguish among elements, compounds, homogeneous mixtures and
heterogeneous mixtures.
 Substances are pure, and include elements (cannot be broken down into simpler substances)
and compounds (which are made up of elements in exact proportions). Examples of
substances are carbon (symbol C) and hydrogen (H), which are elements; and carbon dioxide
(CO2) and water (H2O), which are compounds.
 Mixtures are made up of variable combinations of elements and/or compounds. Mixtures
can be made up of substances evenly mixed throughout (homogeneous mixtures, also known
as solutions) or mixtures can be made of substances that are combined but not dissolved
(heterogeneous mixtures). Examples of mixtures are sugar water and soda, which are
homogeneous mixtures; and soil and oil/vinegar salad dressing, which are heterogeneous
mixtures).
Obj 1.4 Distinguish between physical and chemical properties
 Physical properties are those that are characteristic of a sample of matter without any change
in its identity. Quantitative physical properties (those that can be measured) include
solubility, melting point, boiling point, density, and electrical conductivity. Qualitative
physical properties (that can be described without measuring) include color and physical
state (gas, liquid, or solid).
 Chemical properties describe how a substance reacts with other substances or decomposes to
change identity. A chemical property of iron is that it reacts with oxygen to form iron oxide
(rust), a substance that is quite different from either iron or oxygen.
Obj 1.5 Contrast chemical and physical changes
Chemical changes (also called chemical reactions) occur when substances are changed into
other substances. When plants convert carbon dioxide and water to glucose and oxygen, a
chemical change takes place. All chemical reactions also involve some sort of energy change.
(Energy is the capacity to do work.)
 If energy is given off in a chemical reaction (often as heat), the reaction is classified as
exothermic. Your body undergoes exothermic reactions when it breaks down sugars to
release heat and energy.
 If energy is absorbed in a chemical reaction (an input of energy is needed), the reaction is
classified as endothermic. Photosynthesis is an endothermic, requiring energy from
sunlight to fuel the reaction.
Physical changes refer to changes in a substance's physical properties without a change in its
identity. When water freezes a physical change takes place. But water is water whether solid
(ice), liquid, or gas (steam).
Obj 1.6 Describe the 3 main states of matter and the terms used to describe the temperatures
at which matter changes physical states
Matter is either gas, liquid, or solid. (A fourth state, plasma, will be discussed in another unit.)
Each substance has unique sets of temperature at which it will change to and from gas, liquid
and solid. These temperature at which states change can be useful for identifying and
separating substances.
 When a solid heats up to certain temperature (its melting point) it will change to a liquid
state. When a liquid cools to a certain temperature (its freezing point) it will change to a
solid state.
 When a liquid heats up to a certain temperature (its boiling point) it will change to a gaseous
state. When a gas cools to a certain temperature (its condensation point) it will change to a
liquid state.
A substance's melting and freezing points are usually the same temperature, and its boiling and
condensation points are also usually the same temperature.