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 • 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 • Properties 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
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 ratiosaccording to their masses.
Properties of Compounds • Each compound has its own physical properties and chemicalproperties. • The properties of a compound are different from the properties of the elementsthat 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 chemicalmeans. • Sometimes energy in the form of heatis 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 waterThis is called a homogeneous mixture. It includes saltand water. • Since mixtures are not chemically combined, you can separate the different substances by physicalmethods. • Components in a mixture do not need to be in a specificratio.
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
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 unableto 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 • ColloidA type of mixture in which the particles are dispersed throughout but are notheavy enough to settle out • Particle size is larger than that of a solutionbut smallenough 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