Chapter 5 Lesson 5

Compounds and Chemical Changes

What are Compounds?

• A compound is formed by the combination of two or more elements.

• Compounds have properties different from their elements.

• Compound (Honey Mustard for your chicken nuggets!!)

Names and Formulas

• All compounds have chemical names.

• The chemical name tells scientists which elements come together to make the compound.

• Why are lemons sour?

Names and Formulas

• Lemons are sour because they each contain a chemical called citric acid.

• Citric acid is a weak organic acid found in citrus fruits like grapefruit, oranges, limes and lemons.

• In its pure form citric acid is a white crystalline solid and is sour to taste like all food acids. It is sold as a food additive for cooking and can be found in most supermarkets.

• The molecular formula of citric acid is C6H8O7

What are chemical changes?

• A chemical change occurs when a brand new substance is created, and is completely different from the original substance.

• Rust is a chemical change!

What are chemical changes?• The use of baking soda as a

cleaning medium was created during the Statue of Liberty Renovation from 1984 - 1986. The statue was scheduled to be re-dedicated on July 4, 1986. They needed a cleaning process that would quickly clean the interior of the statue while not damaging the metal structure.

Chemical Equations

• http://www.brainpop.com/science/matterandchemistry/chemicalequations/

• A chemical equation is nothing more than a written expression of a chemical reaction that is to take place or that has already taken place.

• Just like a Math Equation: The math symbol shows the work in answering the problem. The same thing happens in chemistry!

The Law of Conservation of Mass

• Law Of Conservation Of Mass states that- An amount of mass can be converted into equivalent amount of Energy or Work. Such as burning of fuel.

• In Chemistry, it states that in a chemical reaction, the mass being produced and the mass of the reactant are equal.

• (The saying, “you get out of it, what you put into it!”)

Chemical Change

• A chemical change refers to what happens to a chemical when an outside force or influence affects it. Some chemicals may breakdown when left in sunlight. Others may change states when heated or chilled.

• When a molecular bond is broken down and forms a new bond, that is known as a chemical change.

• RESULT: When a chemical change happens, new things are formed or changed entirely!

Types of Chemical Change

• Color change: Bleach removes the color from clothing and you end up with a material that has a different color to it.

• So there is a change. • You get a new material that has different properties

than the materials that you started with. • (The same happens when something RED goes

through the wash, and all the whites are now PINK!)

Color change

Types of Chemical Change

• Tarnish: is a combination of chemicals that have reacted with the metal as a result of being exposed to the air.

• Compare one side of the pan to the other. Tarnish!

Types of Chemical Change

• Release of Gas: What happens when you add Mentos to soda?

• Chemical reaction, and a chemical change as the Mentos dissolves and a gas is released!

• http://dsc.discovery.com/videos/mythbusters-strangest-myths/

Types of Chemical Change

• A precipitate is a solid formed from the chemical reaction or two solutions.

• Soap scum is a white or gray filmy layer that covers the surfaces around our showers, bathtubs, and sinks.

• Soap scum can be found on shower curtains, bathroom fixtures, bathtubs, shower doors, tiling, and more.

Types of Chemical Change

• Example of Precipitate.

• Soap Scum!

Types of Chemical Change

• Release of energy: Heat: Burning wood is a classic chemical change. When wood burns it becomes ash. When it burns it produces heat. This heat is just a product of wood burning and indicates a chemical change.

• Light: Glow sticks are very common in showing that light is an indicator of a chemical change. Among other things, light from fireworks and light from lightning bugs is also a product from a chemical change.

Types of Chemical Change