Download
1 / 65
650 likes | 660 Views
Learn about atoms, elements, compounds, and mixtures, distinguishing between pure substances and combinations. Understand the concepts of solutions, homogeneous and heterogeneous mixtures. Discover the properties and classifications of different types of matter.
E N D
Pure Substances • A sample of matter that has definite chemical and physical properties. Atoms Elements Compounds Molecules
Elements • pure substance that cannot be separated into simpler substance by physical or chemical means.
Elements • In 1813, a system of representing elements with symbols was introduced. • Each symbol consists of one or two letters. • Two letters are needed for a chemical symbol when the first letter of that element’s name has already been used.
Compounds Pure substance composed of two or more different elements joined by chemical bonds. • Made of elements in a specific ratio that is always the same • Has a chemical formula • Can only be separated by chemical means, not physically H2O NaCl CO2
Compounds • Compounds are also pure substances. • Water is a compound. • Water can be broken down into simpler substances – hydrogen and oxygen.
Mixtures • A combination of two or more pure substances that are not chemically combined. • substances held together by physical forces, not chemical • No chemical change takes place • Each item retains its properties in the mixture • They can be separated physically Chem4kids.com
Is it uniform throughout? • If the answer is yes, the matter is homogeneous (looks the same throughout). • That leads us to another question.
Homogeneous Mixtures • A mixture that appears to be the same throughout. • It is “well mixed.” • The particles that make up the mixture are very small and not easily recognizable.
Examples of homogeneous mixtures Milk, toothpaste, and mayonnaise are homogeneous mixtures.
Solutions • A solution is a type of homogeneous mixture formed when one substance dissolves in another. • It is the best mixed of all mixtures. • A solution always has a substance that is dissolved and a substance that does the dissolving. • The substance that is dissolved is the solute and the substance that does the dissolving is the solvent.
Water as a solvent • Many liquid solutions contain water as the solvent. • Ocean water is basically a water solution that contains many salts. • Body fluids are also water solutions.
SOLUTIONS HAVE 2 PARTS • SOLUTE – The substance being dissolved • SOLVENT- The substance doing the dissolving • sugar=solute • Water = solvent
Types of solutions Solute Solvent Example Metals dissolved in metals are called alloys.
Alloys Stainless steel is a mixture of iron and chromium. Brass is an alloy of copper and zinc.
Is it uniform throughout? • If the answer is no, the matter is a heterogeneous mixture. • Considered the “least mixed.” • Does not appear to be the same throughout. • Particles are large enough to be seen and to be separated from the mixture.
Examples of heterogeneous mixtures • Sand and pebbles • Oil and water • Powdered iron and powdered sulfur
COLLOID – a liquid mixture - can be considered a homogeneous and sometimes heterogeneous mixture ex: milk SUSPENSION – a liquid mixture - heterogeneous -ex: Italian dressing
Colloids • In a colloid the particles are mixed together but not dissolved. • The particles are relatively large and are kept permanently suspended.
Colloids • A colloid will not separate upon standing. • The particles are constantly colliding, and this allows a colloid to scatter light – thus colloids often seem cloudy.
Examples of homogeneous mixtures Milk, toothpaste, and mayonnaise are homogeneous mixtures. THESE ARE EXAMPLES OF COLLOIDS
Mixtures vs. Compounds http://www.bbc.co.uk/schools/ks3bitesize/science/chemistry/elements_com_mix_6.shtml
Can you identify the following? You will be shown a series of photos. Tell if each photo represents an item composed of an element, compound, or mixture. Review: • An element contains just one type of atom. • A compound contains two or more different atoms joined together. • A mixture contains two or more different substances that are only physically joined together, not chemically. • A mixture can contain both elements and compounds.
Element, Compound, or Mixture? Cu Copper
Element, Compound, or Mixture? Jelly Beans
Element, Compound, or Mixture? Jelly Beans
Element, Compound, or Mixture? Table Sugar
Element, Compound, or Mixture? Table Sugar C12H22O11
Element, Compound, or Mixture? Diamond
Element, Compound, or Mixture? C Diamond
Element, Compound, or Mixture? NaCl Salt
Element, Compound, or Mixture? Neon Gas
Element, Compound, or Mixture? Ne Neon Gas
Element, Compound, or Mixture? Pure Water
Element, Compound, or Mixture? H2O Pure Water
