Chapter 2 2.1 Classifying Matter

2.1 Classifying Matter Examples: ___________-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______composition because 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

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.

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__________can be 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__________the substances 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