Presentation on theme: "What are the 2 types of pure substances? Elements Compounds."— Presentation transcript:
What are the 2 types of pure substances? Elements Compounds
Elements are the simplest substances. Elements CANNOT be separated into simpler substances through any chemical reaction or physical change.
If the substance is an element, the smallest particle is an ATOM. Sulfur What is sulfur’s atomic number? 16 Elements are identified by their atomic numbers. (Number of protons)
Compounds are formed when elements are chemically bonded in a definite ratio. Compounds CAN be separated into simpler substances through chemical reactions.
How can you tell the difference between elements and compounds if you are told their names? Elements will be found directly on the P ERIODIC T ABLE OF THE E LEMENTS while compounds are NOT directly found on the table, but are two or more elements combined. (Ex: H 2 O – H and O.) HINT: Every element is either abbreviated with a single CAPITAL letter (H) or one CAPITAL letter and one lowercase letter (Li). Therefore, when you are trying to decide if a substance is an element or compound – count the capital letters!
Decide if the substances listed on your notes are elements or compounds. Hint: Only two of the substances are elements. compound element compound
Mixtures are formed when substance are placed together which will not chemically react. Mixtures CAN be separated based on the physical properties of the substances in the mixture. Iron and Sulfur mixed together.
There are two main categories of mixtures. Heterogeneous Mixtures Homogeneous Mixtures The substances within the mixture are distinct and easily identified. The substances within the mixture are blended evenly together.
Mixtures are NOT formed with any kind of definite ratio. While brass is a mixture of copper and zinc, there is not an exact recipe and different manufacturers will use a slightly different percentage of each metal. Brass Copper Zinc
Solutions Solutions one of the most common forms of mixtures. They are created when substances are evenly mixed together. Solution = Homogeneous Mixture Aqueous solutions are formed with solutes are dissolved in water Alloys are formed when metals are evenly mixed together. Gaseous solutions, like air, formed when gases mix together.
Important Fact: An alloy is made when metals are mixed together. The metals are melted together and mixed. They can be separated by melting the alloy. When a solid has melted completely into a liquid, we say that it is molten. Is melting a physical or chemical change? Melting is a physical change. This means that alloys are NOT a new substance. They are simply a mixture of substances.
Common Alloys Steel (Iron and Nickel Alloy) Brass (Copper and Zinc Alloy) Bronze (Copper and Tin Alloy)
Let’s take a look at a few different ways to separate mixtures: Sifted/filtered Magnetism Distillation Separatory Funnel (density)
While volume, sometimes simply referred to as size and shape, is related to the size of a sample and it can be used to separate a substance from a heterogeneous mixture. If one substance is in larger pieces than the other, the larger substance can be sifted or filtered from the mixture.
Some elements can be separated from heterogeneous mixtures based on the physical property of magnetism. In particular these elements are iron, cobalt, and nickel. Together these elements are known as the Iron Triad.
Distillation is a process that is used to separate a liquid from a homogeneous mixture based on differences in boiling point. 1. Water is evaporated from the solution 2. The evaporated water is cooled and condenses back into a liquid 3. The pure, distilled water is collected. Distillation
Distillation can also be used to separate two liquids which have been dissolved together. Liquids that can be evenly mixed together are known as miscible liquids. Miscible liquids are either both polar or both nonpolar.
Oil and water are immiscible because one is polar and the other in nonpolar. Oil Water Based on this picture, which liquid is more dense: oil or water?
Immiscible liquids can be separated very easily using a device known as a separatory funnel. Notice that this device also separates heterogeneous mixtures based on the property of density.