Elements, Compounds, & Mixtures Chapter 4 Elements, Compounds, & Mixtures

3.1 Elements Element- A pure substance that cannot be separated into simpler substances by chemical or physical means. Pure Substance- A substance in which there is only one type of particles

Properties of Elements Each element has its own characteristic properties. These include boiling/melting point, density, reactivity, flammability, etc. An element may share one or two properties with another element, but it will not share all its properties with another element. There will be specific properties for each element.

Classifying Elements You can use properties to identify elements. Think about how many types of dogs there are. How do you tell one breed from another? Categories of Elements Metals Nonmetals Metalloids

Classifying Elements Metal- an element that is shiny and conducts heat and electricity well Properties Malleable – ability to be hammered into sheets Ductile – ability to be drawn into wires

Classifying Elements 1.some are shiny Nonmetal – an element that conducts heat and electric poorly Properties 1. dull 2. brittle – not malleable Metalloid- an element that has properties of metals and nonmetals 1.some are shiny 2. some are dull 3. somewhat malleable and ductile 4. some are good conductors of heat and electricity 5. some are poor conductors of heat and electricity

Classifying Elements

Classifying Elements Appearance Conductivity Physically Example Metal   Appearance Conductivity Physically Example Metal  Shiny Good malleable., ductile Lead, Copper Nonmetal  Dull Poor Brittle Sulfur, oxygen Metalloid Some Shiny/ some dull Some good/ some poor Somewhat malleable and ductile Silicon, boron

3.2 Compounds Compound- a substance made up of atoms of two or more different elements joined by chemical bonds Examples: H2O (water), NaCl (table salt) A particle of a compound is called a molecule Elements do not randomly combine. They join into a specific ratios according to their masses.

Properties of Compounds Each compound has its own physical properties and chemical properties. The properties of a compound are different from the properties of the elements that form it. Sodium + Chlorine  Table Salt Explosive soft metal Yellow Piousness Gas

Breaking Down Compounds Some compounds can be broken down into their elements or simpler compounds by chemical means. Sometimes energy in the form of heat is needed to do this.

3.3 Mixtures Mixture- A combination of two or more substances that are not chemically combined. An example would be a salad (or salsa as in the picture). The cheese, sauce, and dough are still the same items after you make the pizza.

Properties of Mixtures Sometimes you cannot see all the components like in salt water This is called a homogeneous mixture. It includes salt and water. Since mixtures are not chemically combined, you can separate the different substances by physical methods. Components in a mixture do not need to be in a specific ratio.

Separating Mixtures Sometimes you can just pick ingredients out of a mixture (pizza) Other ways to separate mixtures include: evaporation – separates a mixture based on boiling points Ex: salt in water magnet – anything ferromagnetic will stick to the magnet EX. Iron & Aluminum nails in box distillation – separates a mixture based on density. Ex: crude oil – gasoline & propane centrifuge – separates based on particle size Ex: blood

Compounds vs. mixtures Mixtures Compounds Made of elements, compounds or both Made of elements No change in original properties of components Change in original properties of components Separated by physical means Separated by chemical means Formed by using any ratio of components Formed using a set ratio of components

Mixture vs. compound vs. element

Solutions, Suspensions, & Colloids

Solutions Solution- A mixture that appears to be a single substance. Particles are small & cannot be filtered Solutions have the same composition throughout. Example: Salt Water Solute- Substance that is dissolved. (Salt) Solvent- The substance in which the solute is dissolved. (water)

Solutions Continued The term soluble means able to dissolve. Insoluble means unable to dissolve. Solutions can be solids, liquids, or gases. Solubility- Measure of the amount of solute dissolved in a solvent. This is expressed as g/mL To increase solubility: heat stir crush – smaller particles  

Colloids Colloid A type of mixture in which the particles are dispersed throughout but are not heavy enough to settle out Particle size is larger than that of a solution but small enough they will still pass through a filter. Examples of colloids: milk, fog

Colloids Colloids scatter light. (fog) You can actually see the beam of light in the colloid.

Suspensions Suspensions- A mixture in which the particles of a material are dispersed throughout a liquid or gas but are large enough that they settle out. Particles are large enough to settle out. Suspensions can be separated by passing through a filter. Examples: Italian salad dressing, muddy water

Elements, Compounds, Mixtures   Elements Compounds Mixtures How many parts make it up?  1  2 or more  2 or more elements or compounds Pure: more than one substance?  pure  Not pure Chemically or physically combined?  N/A  Chemically physically Chemical change to make them?  Yes no Fixed ratio? Yes How separated: chemically/ physically? Chemically

Solution, suspension, colliod   Elements Compounds Mixtures How many parts make it up?  1  2 or more  2 or more elements or compounds Pure: more than one substance?  pure  Not pure Chemically or physically combined?  N/A  Chemically physically Chemical change to make them?  Yes no Fixed ratio? Yes How separated: chemically/ physically? Chemically