Chapter 2 Properties of Matter

Section 2.1: Classifying Matter Key Concepts Why are elements and compounds classified as pure substances? How do mixtures differ from pure substances? What is the main difference among solutions, suspensions, and colloids?

Section 2.1: Classifying Matter Pure Substances A pure substance is matter that always has exactly the same composition or make up. EVERY sample of a given substance has the same properties because a substance has a fixed, uniform composition.

Section 2.1: Classifying Matter Elements There are about 100 known elements in the world!!! An element is a substance that can NOT be broken down into simpler substances.

Section 2.1: Classifying Matter Element (cont) An element has a fixed composition because it contains only one type of atom. What is an atom?

Section 2.1: Classifying Matter Elements (cont) Of the over 100 elements that exist: MOST elements are solids at room temperature. Some are gases at room temperature. Only 2 are liquids at room temperature, bromine and mercury which are both extremely poisonous.

Section 2.1: Classifying Matter

Section 2.1: Classifying Matter Element (cont) In 1813, Jons Berzelius, a Swedish chemist suggested that chemists around the world use a standard set of symbols to represent elements.

Section 2.1: Classifying Matter Elements (cont) These symbols as well as other information is shown in the Periodic Table of Elements. This table allows scientists who speak different languages to use the same information.

Section 2.1: Classifying Matter

Section 2.1: Classifying Matter Compounds A compound is a substance that is composed of two or more simpler substances and can be broken down into these substances. Example: Water!!!

Section 2.1: Classifying Matter Mixtures Think about an example of two things you mix together regularly…chocolate syrup and milk to give you chocolate milk!!! Chocolate milk is an example of a mixture. Think about another example and write it down.

Section 2.1: Classifying Matter Mixtures (cont) The properties of a mixture can vary because the composition of a mixture is NOT fixed. There are 2 types of mixtures: 1.) Heterogeneous Mixture 2.) Homogeneous Mixture

Section 2.1: Classifying Matter Mixtures (cont) A heterogeneous mixture has the parts of the mixture which are noticeably different.

Section 2.1: Classifying Matter Mixtures (cont) A homogeneous mixture is a mixture where the substances are so evenly distributed that it is difficult to tell the different pieces apart.

Section 2.1: Classifying Matter Solutions, Suspensions and Colloids The three terms solution, suspension and colloid are all used to describe a mixture…the difference in the terms has to do with the size of the particles in the mixture.

Section 2.1: Classifying Matter Solutions, Suspensions and Colloids When a substance dissolves to form a homogeneous mixture the mixture is called a solution. Example from class: Salt mixed with water gives you salt water.

Section 2.1: Classifying Matter Solutions, Suspensions and Colloids A suspension is a heterogeneous mixture that separates into layers over time. Example from class: Spray paint must be shaken before use so it is a suspension.

Section 2.1: Classifying Matter Solutions, Suspensions and Colloids A mixture that contains particles that are not as small as those in a solution but not as large as those in a suspension are called colloid. Example of a colloid: Fog is a colloid of air and water.

Section 2.2: Physical Properties Examples of Physical Properties A physical property is any characteristic of a material that can be observed and measured.

Section 2.2: Physical Properties 5.) density 6.) boiling point 7.) melting point Examples of Physical Properties There are 7 physical properties we will talk about: 1.) maleability 2.) conductivity 3.) viscosity 4.) hardness

Section 2.2: Physical Properties Viscosity A liquids resistance to flowing is called its viscosity. When heated a liquids viscosity decreases. Example: Cooking oil when it is heated in the frying pan it flows much easier.

Section 2.2: Physical Properties Conductivity A materials ability to conduct heat is its conductivity. Materials such as metals that conduct heat well also conduct electricity well and are called conductors.

Section 2.2: Physical Properties Malleability Maleability is a materials ability to be hammered and not shatter. What happens when you hit a piece of metal with a hammer and what happens when you hit a piece of glass?

Section 2.2: Physical Properties Hardness Hardness is a materials ability to resist scratching or bending. What is the hardest substance on earth?

Section 2.2: Physical Properties Melting Point A substances melting point is the temperature at which it turns from a solid into a liquid.

Section 2.2: Physical Properties Boiling Point The boiling point of a substance is the temperature at which a substance vaporizes.

Section 2.2: Physical Properties Density Density = Mass / Volume Pure substances will ALWAYS have the same density so, a substances density can be measured to determine it’s purity.

Section 2.2: Physical Properties Using Physical Properties You can use the physical properties of a substance to do 2 things: 1.) To Identify a Material 2.) To Choose a Material

Section 2.2: Physical Properties Using Properties to Identify Materials The physical properties of a substance are constant so they can be measured to find out what something is made of. This is a very common techniques used by crime scene investigators.

Section 2.2: Physical Properties Using Properties to Choose Materials The physical properties of a substance can be looked at and measured to determine how well they would work in a given situation.

Section 2.2: Physical Properties Using Properties to Separate Mixtures The physical properties of certain substances can be used to help separate them from mixtures. There are 2 ways to separate mixtures: 1.) Filtration 2.) Distillation

Section 2.2: Physical Properties Filtration The size of a particle is used to separate substances from a mixture by a process called filtration.

Section 2.2: Physical Properties Distillation Distillation is a way of separating substances based on their boiling points. Substances with a lower boiling point will boil before a substance with a higher boiling point.

Section 2.3: Chemical Properties Observing Chemical Properties At chemical property is any property that alters the composition of matter Chemical properties can only be observed when one substance changes into another.

Section 2.3: Chemical Properties Flammability Flamability is a substances ability to burn in the presence of oxygen.

Section 2.3: Chemical Properties Reactivity The property used to describe how quickly a substance will combine with another substance is its reactivity.

Section 2.3: Chemical Properties Recognizing Chemical Changes A chemical change occurs when a substance reacts and forms one or two more substances. There are 3 types of evidence: 1.) Change in Color 2.) Production of a Gas 3.) Formation of Precipitate

Section 2.3: Chemical Properties A Change in Color The lighting of a match causes a change in color that can be seen as going from a red match head and after burning it turns back.

Section 2.3: Chemical Properties Production of a Gas Mixing baking soda and vinegar causes a chemical reaction that can be seen by producing carbon dioxide gas.

Section 2.3: Chemical Properties Formation of Precipitate When a solid forms and separates from a liquid a precipitate has been formed. When vinegar is added to milk a glob like precipitate forms.

Section 2.3: Chemical Properties Is a Change Chemical or Physical? When a substance undergoes a chemical change the composition of the matter changes. When a substance undergoes a physical change the composition of the matter stays the same.