did you know? matter is changing around you all the time. some changes are physical and some are...

Did you know?

• Matter is changing around you all the time. Some changes are physical and some are chemical

Do you remember what Physical Properties are???

• Color

• Shape

• Mass

• Volume

• State of Matter

• Length

• Magnetism

• Texture

• Density

After a PHYSICAL CHANGE, the appearance of the substance may be different but it is still the same substance

• A physical change does not produce a new substance – molecules are the same

What does this mean?

• Only one substance goes into the reaction and one substance comes out.

Water Water

Physical property: States of Matter

Cutting a Steak

Steak

Steak

What physical property changed?

• State of matter– Size, shape, mass, volume

• Is it still the same substance? – This is a physical change because before and after

being cut the substance is still steak even if the size, shape, and other physical properties changed. It changed from one bigger piece into smaller pieces but no new substance was produced.

Bending Metal Wires

Metal wires

Metal wires

What physical property changed?

• What physical property changed?– Shape

• Why is this a physical change?– Bending metal wires is a physical change because

a physical change means that no new substance is produced. Although the wires look different they are still the same substance, metal. It just changed shape from flat to bent.

Ice Cream Melting

Ice cream

Ice cream

What physical property changed?

• State of matter– Solid Liquid

• Is it still the same substance? – This is a physical change because in a physical

change the substance stays the same even if it looks different. The only thing that changed about the ice cream is its state of matter (solid to a liquid) but it is still ice cream after it melts.

Exit Ticket

1) A pencil being sharpened

• Evidence: What physical property changed?

• Reasoning: Why is this a physical change?

2) Water condensing on your winshield

• Evidence: What physical property changed?

• Reasoning: Why is this a physical change?

Breaking glass

• What physical property changed?– Shape, volume, texture, mass, etc.

• Is it still the same substance?– Yes! Still glass– Why? It just changed from one piece to a

bunch of smaller pieces

Glass Glass

Chemical Properties

• Describes matter based on its ability to change into a new substance with different properties

Chemical Properties

• These properties can only be observed during a chemical reaction

• A chemical change has to take place in order to observe them!!!

Chemical Properties

• Flammability– Does it burn?– How likely is it to burn?

Flammability

• Can you think of any substances that are very flammable?– Gasoline– Paper– Wood

Flammability

• Can you think of any substances that are not flammable?– Water

Examples of Chemical Properties

• What is a reaction? What are some examples of types of reactions?

• Reactivity

Examples of Reactivity

• Reacts with oxygen– What happens when this substance reacts

with oxygen?

Reacting with oxygen

• Rust!– When exposed to oxygen for long periods

of time, metal will react with the oxygen to form RUST

Examples of Reactivity

• Reacts with water– What happens to the substance when it

interacts with water?

Examples of Reactivity

• Example:

• Alka Seltzer and water

Example #1

• You light a candle.

• Flammability or Reactivity?– Flammability

• How do you know?– It describes the substance’s ability to burn.

A candle can burn easily, therefore it is flammable.

Example #2

• Vinegar will react with baking soda.

• Flammability or Reactivity?– Reactivity

• How do you know?– Vinegar is reacting with baking soda and

carbon dioxide is produced. This describes the interaction between two substances.

Example #3

• Yeast acts on sugar to form carbon dioxide and ethanol

• Flammability or Reactivity?– Reactivity

• How do you know?– Yeast is reacting with sugar and forms two

new substances, carbon dioxide and ethanol.

Example

• When charcoal burns in a BBQ grill

• Reaction between Carbon and Oxygen

• Provides heat that cooks the dinner and gives off CO2

After a CHEMICAL CHANGE, a NEW substance is produced with NEW properties. These properties are different from the original substance!

A new substance is formed!

Signs that a Chemical Change took place

• Production of a gas– Often appearing as bubbles– If it involves FIRE it involves gas (carbon

dioxide in the smoke)

Signs that a Chemical Change took place

• Change in temperature– Such as the production or loss of heat

Endothermic reaction

• A chemical reaction resulting in the loss of heat

Endothermic reaction

• Example: Ammonium nitrate and water in ice packs

Exothermic reaction

• Exothermic reaction: A chemical reaction resulting in the production of heat

Exothermic reaction Example

• Example: Hand warmers– Iron reacts with oxygen to produce heat

Iron & Oxygen heat

Signs that a Chemical Change took place

• New color– A chemical reaction results in a color

change– Metal and oxygen react to form RUST– Color changes from silver to brownish red

Signs that a Chemical Change took place

• Formation of a precipitate

• An insoluble solid that forms out of a water solution

• It forms because the solid does not dissolve in water

Example #1: Burning wood

Example #1: Burning wood

• What chemical property is present?– Flamability

• What is the evidence of a chemical change?– Production of a gas (SMOKE)– Change in temperature

• Is it still the same substance? – No! Ashes

Example #3: Digestion of Pizza

Example #3: Digestion of Pizza

• What chemical property is present?– Reactivity

• What is the evidence of a chemical change?– New substances with new properties– Food is broken down by acid

• Is it still the same substance? – No! – Food is broken down into other substances (basic

molecule types)

Example #2: Rusting of Metal

Example #2: Rusting of Metal

• What chemical property is present?– Reactivity

• What is the evidence of a chemical change?– Change in color– Silver to reddish brown

• Is it still the same substance? – No! Different properties

Physical or Chemical???Use the A-F cards to separate the Physical Changes from the

Chemical Changes!

A. You cut a sheet of aluminum foil in half

B. You leave the milk on the counter all night and discover it has soured in the morning

C. Your Mom lights a candle in a dark room

D. Rubbing alcohol evaporates from your hand

E. Hydrogen peroxide bubbles when you put it on a cut on your leg

F. Your friend melts some butter for her popcorn