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Physical and chemical properties. What are physical properties?. A physical property is a characteristic that can be observed or measured without changing the identity of a substance. Mass, volume, color, hardness, magnetism, and weight are all physical properties. Which one is motor oil?.
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What are physical properties? • A physical property is a characteristic that can be observed or measured without changing the identity of a substance. Mass, volume, color, hardness, magnetism, and weight are all physical properties.
Which one is motor oil? How did you know?
Which one is rubbing alcohol? What could we use to find out?
Which one is rubbing alcohol? • Smell
Which one is rubbing alcohol? • Smell • Density
Which one is rubbing alcohol? • Smell • Density • Mass
Which one is rubbing alcohol? • Smell • Density • Mass • Evaporation rate (boiling point)
Which one is rubbing alcohol? • Smell • Density • Mass • Evaporation rate (boiling point) • Freezing point
Other physical properties • Hardness • Magnetic abilities • Color • Strength
Chemical properties • A chemical property is a characteristic that describes how a substance will interact with other substances during a chemical reaction. Examples of chemical reactions include the ability to burn, rust, react to light as well as how likely it is to bond with other elements.
Rust combines metal with oxygen to produce a different material. Photosynthesis uses sunlight to react with chlorophyll to produce food for the plant. The heat from the fire breaks down the wood’s molecules and recombines them with oxygen.
Chemical properties can help us identify substances • Chemical properties are much harder to see. Which of the two will burn?
Chemical properties can help us identify substances • Chemical properties are much harder to see. Which of the two will burn? Water Alcohol
What does that mean • Alcohol and water look the same. While the density is different you would need a scale to tell the difference. The chemical property of alcohol that allows it to burn is obviously different than that of water however. • Looks can be deceiving!!
Why is burning a chemical change? • https://www.youtube.com/watch?v=_074G_bk5sY
Why is burning a chemical change? • https://www.youtube.com/watch?v=_074G_bk5sY • Could you recover the match in it’s original form after the burn?
Why is burning a chemical change? • https://www.youtube.com/watch?v=_074G_bk5sY • Could you recover the match in it’s original form after the burn? Why not?
Which is a physical change and which is a chemical change? • https://www.youtube.com/watch?v=6bsVlKYTFGE • The firecracker underwent what type of change?
Which is a physical change and which is a chemical change? • https://www.youtube.com/watch?v=6bsVlKYTFGE • The firecracker underwent what type of change? • The playdough went through what type of change?
Which is a physical change and which is a chemical change? • https://www.youtube.com/watch?v=6bsVlKYTFGE • The firecracker underwent what type of change? • The playdough went through what type of change? Do all the pieces of playdough have the same properties that they had when they were part of the whole?
What to look for to determine physical change. • The substance does not change from it’s original composition. (Torn paper is still paper) • There is no production of a new substance due to a physical change. (Sugar dissolved in water is still sugar and water) Still a pencil
What to look for in a chemical change • Fizzing or production of gas. • Change in color • Change in density Indigo Carmine solution
Summary PhysicalChange ChemicalChange A chemical change occurs when one or more elements combine. This forms new molecules or forms different compounds than what were started with. After a chemical change, you are left with totally different by-products and can not undo the change to get what you started off with back. • A physical change is when something changes what can be observed about the substance without changing the substance from it’s original condition. • A physical change does not change the essence of the original substance.