Chapter 2. 2.1 Classifying Matter. 2.1 Classifying Matter. ___________- Matter that always has exactly the same composition. There is a fixed, uniform composition. Substances can be classified into two categories: Elements
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Chapter 2 2.1 Classifying Matter
2.1 Classifying Matter • ___________-Matter that always has exactly the same composition. There is a fixed, uniform composition. • Substances can be classified into two categories: • Elements • A substance that cannot be broken down into simpler substances. There are just over _____elements. • _____- The smallest particle of an element. • An element has a______compositionbecause it contains only one type of atom. • No two elements contain the ___________of atom. • Examples:
Pure Substances Con’t. • Compounds • A substance that is made from two or more _______ substances and can be broken down into those simpler substances. • The ___________ of a compound differ from those of the substances from which it is made. • A compound always contains two or more elements joined in a _________________.
Mixtures • Mixtures tend to retain _______of the properties of their individual substances. • The properties of a mixture can vary because the composition of a mixture is ____fixed. • ________________Mixtures- The parts of the mixture are noticeably different from one another. Examples: salads, salsa
Mixtures • Homogeneous Mixtures - The substances are so _________________that it is difficult to distinguish one substance in the mixture from another. • Examples:
Solutions, Suspensions, and Colloids • Based on the size of its largest particles, a mixture can be classified as a _________, ____________, or ______________. • Solution- Substances dissolve and form a ______________ mixture. • Examples: • Suspensions- Heterogeneous mixture that separates into ______ over time. • Examples:
Solutions, Suspensions, & Colloids • Colloids- Contains some particles that are _________ in size between the small particles of solutions and the large particles of suspensions. Colloids will not separate and _____ be filtered. However, colloids will scatter light. (_____________) • Example:
Section 2.2 Physical Properties • Physical property- Any characteristic of a material that can be ______________ without changing the ______________of the substance in the material. • Examples: viscosity, conductivity, malleability, hardness, ____________, boiling point, and____________.
Physical Properties • _________- The tendency of a liquid to keep from flowing. A resistance to flowing. • Example: _______ has a high viscosity. • Conductivity- A material’s ability to allow _____ to flow. • Example: _________over a stove. • Materials with a high conductivity are called _________. They are also a good conductor of electricity as well. Wood is a _______ conductor.
Physical Properties • Malleability- The ability of a solid to be _____________________without shattering. • Example: Most__________canbe made into coins or foil. Because gold is both malleable and beautiful, it is often used to make jewelry. These ancient gold medallions were made to form a necklace
Physical Properties • Hardness- One way to compare harness of two materials is to see which of the materials can _______ the other. Stainless steel knife blades can scratch ______. _______ is the hardest known material. This Tlingit carver is using an adze to carve a canoe from Western red cedar. Red cedar is a relatively soft wood
Physical Properties • Melting Point- Temperature at which a substance changes from a ___________. Example: Ice melts because the melting point of water is 0ºC (32ºF). • Boiling Point- Temperature at which a substance changes from a _____________or vapor. The table lists the melting points and boiling points for several substances.
Physical Properties • Density-________of the ______ of a substance to its _____. This can be used to test the purity of a substance. • Examples: ________ has a density of 10.5 g/cm3.
Using Physical Properties • Physical properties are used to _________ a material, to _______a material for a specific purpose, or to__________thesubstances in a mixture. • Using properties to identify materials • First, decide which properties to____ • Second, do tests on the ________sample • Third, compare results with a ______ sample • (This is used in crime scene investigations) • Using properties to choose materials • Properties determine which materials are _______ for which uses. Example: shoelaces wouldn’t be made from______ wood.
Using Physical Properties • Using properties to separate mixtures • __________ and __________ are two common separation methods. • Filtration- A process that separates materials based on the _____ of their particles. Example: brewing coffee • Distillation- A process that separates the substances in a solution based on their ________________. Example: Separate freshwater from seawater.
Recognizing Physical Changes • Physical change- Occurs when some of the ________ of a material change, but the substances in the material remain the ______. Examples: Braiding hair and cutting hair are examples of physical changes. Braiding is a reversible change. Cutting cannot be reversed
2.3 Chemical Properties • Chemical property- Any ability to produce a change on the __________ of matter. • Chemical properties can only be observed when the substances in a sample of matter are changing into ________________. • Examples:
Chemical Properties • Flammability- A material’s ability to ____ in the presence of oxygen. Examples: Anything that can be used as a _____. _______________. • Reactivity- Describes how readily a substance __________ chemically with other _______. Example: Iron with oxygen and water will form _____ if you leave your bike out in the rain.
Recognizing a Chemical Change • Chemical change- Occurs when a substance ______ and forms one or more ___ substances. Examples: baking cakes, food digesting. • Three common types of evidence for a chemical change are a change in ______, production of a _____, and formation of a ______________.
Evidence for a Chemical Change • Color Change • Silver bracelets will _______. (tarnish) • Matches _____ and turn ________. • Copper roofs turn _____.(patina)
Evidence for a Chemical Change • Production of a gas • Mixing vinegar with baking soda (_____________ gas) • Cakes have gas _______ in it
Evidence for a Chemical Change • Formation of a precipitate • Precipitate- _____form and separate from a _______ mixture • _______ of milk- adding lemon juice
Is a Change Chemical or Physical? • Sometimes gas bubbles or color change is not a chemical change. You must ask yourself: Are _______ substances present ________the change takes place. • When matter undergoes a chemical change, the ________ of the matter changes. When matter undergoes a physical change, the composition of the matter _______________. A blacksmith uses a hammer to shape a horseshoe that has been heated. Although the color of the iron horseshoe changes, ______________change is occurring