Chapter 2 Matter and Change

What is matter?  Matter is defined as anything that has mass and takes up space. atoms- smallest unit of an element that maintains the properties of the element. atoms- smallest unit of an element that maintains the properties of the element. element- pure substance made of only one kind of atom. element- pure substance made of only one kind of atom. compound- substance that is made from the atoms of two or more elements that are chemically bonded. compound- substance that is made from the atoms of two or more elements that are chemically bonded.

What is the difference between mass and weight?  An objects mass is the amount of matter the object contains. Mass differs from weight because it is the force that measures the pull of gravity on a given mass. Mass differs from weight because it is the force that measures the pull of gravity on a given mass. Your mass stays the same regardless of your location, but your weight may change depending upon gravity. Your mass stays the same regardless of your location, but your weight may change depending upon gravity.

Extensive and Intensive Properties  Every substance has characteristic properties. Extensive properties- depend on the amount of matter present. Extensive properties- depend on the amount of matter present. Examples: length, volume, massExamples: length, volume, mass Intensive properties- do not depend on the amount of matter present. Intensive properties- do not depend on the amount of matter present. Color, temperature, density, melting pointColor, temperature, density, melting point

Physical  Physical properties- characteristics that can be observed or measured without changing the identity of the substance. Physical Change- A change that does not involve a change in the identity of the substance. Physical Change- A change that does not involve a change in the identity of the substance. Examples: melting, freezing, color, breaking, dissolving, cutting, density Examples: melting, freezing, color, breaking, dissolving, cutting, density

Chemical  Chemical properties- relate to a substance’s ability to undergo change that transforms it into a different substance. Chemical Change- A change in which one or more substances are converted into different substances Examples: burning, reacting, baking, flammability, solubility

Classification of Matter  Matter can be classified into two categories: Pure substances: contain only one type of matter Pure substances: contain only one type of matter Mixtures: contain more than one type of matter Mixtures: contain more than one type of matter

States of Matter-Solids  Solids have a definite shape and volume. The particles are packed tightly together as seen to the right.  As the temperature is raised, the particles begin to move faster, causing the solid to transform into a liquid.  For example, ice melting to water.

States of Matter-Liquids  Liquids have a fixed volume, but they take the shape of the container.  The particles of a liquid are farther apart than a solid, but closer than a gas.  As the liquid is heated, the particles begin to move faster causing the liquid to transform into a gas.  For example, water boiling to steam.

States of Matter-Gas  Gases take both the shape and volume of the container.  The particles of a gas are spaced very far apart, and are moving very quickly.

Endothermic and Exothermic Endothermic reactions takes in energy as heat from the surroundings Example: melting and boiling solid  liquid  gas Exothermic reactions energy is given off Example: freezing Gas  liquid  solid

Endothermic vs. Exothermic A potential energy graph of an endothermic reaction: A potential energy graph of an exothermic reaction:

Activation Energy  Activation energy is the minimum amount of energy that must be put into a system to start a chemical change  Endothermic reactions are not as favored as exothermic reactions in nature, but they do occur if sufficient source of energy is available

Types of Mixtures  A mixture is a blend of two or more substances. Homogeneous mixtures are completely uniform in composition. Homogeneous mixtures are completely uniform in composition. Examples are salt water, sugar waterExamples are salt water, sugar water Homogeneous mixtures are also known as solutions.Homogeneous mixtures are also known as solutions. Heterogeneous mixtures are not uniform in composition Heterogeneous mixtures are not uniform in composition Examples are oil and vinegar, vegetable soupExamples are oil and vinegar, vegetable soup

Methods of Separating Mixtures  Physical separation: physically picking out large pieces of matter.  Distillation: A liquid is boiled to produce a vapor that is then condensed again to a liquid.  Chromatography: Separation of liquids based on solubility