Changing Matter
Define physical change
any change to the physical properties of matter, such as it's size, shape or state (solid, liquid, gas); no new substance is created
Define physical property
Properties that we observe using our senses; the way something looks/smells/tastes/feels
What is one physical change I could do to an object in this classroom?
Answers will vary
What is a precipitate?
A solid that forms as a result of a chemical reaction.
It does not dissolve.
Define reactants
The chemicals on the LEFT side of the equation; the chemicals we start a reaction with
Define chemical change
when matter changes into new substances with new properties; new substance is created
Define chemical property
the way a substance may change, or react, to form other substances; describes the reactivity of a substance
Give three examples of physical changes
Melting butter, tearing paper, crushing a can, freezing water, dissolving koolaid, cutting your hair.
Give three examples of chemical changes
Copper reacts with oxygen and turns green, dying your hair, baking bread,etc.
Define products
The chemicals on the RIGHT side of the equation; the chemicals that we end a reaction with
Why is milk souring a chemical change?
A new substance has been created. Bacteria feed off of the sugars in milk and they produce lactic acid. We can't reverse this change.
Give three examples of physical properties
Color, size, shape, density, solubility, odor
Explain why phase changes are physical changes and not chemical changes.
No new substance is created: all of the molecules are still the same, we are just either adding or taking away heat.
What are the signs we look for to tell if a chemical change has taken place?
Never Give Elephants Old Cell Phones
New Substance, Gas produced, energy change, Odor, color change, precipitate
Define balanced chemical equation
I have a beaker of water that undergoes a physical change. Describe what the molecules in this sample will look like after the change.
Give two examples of chemical properties
Flammability, reactivity with light/oxygen/water etc.
Draw a picture of the molecules in a substance before and after a physical change
Molecules should be the same
What is one chemical change I could do to an object in this classroom?
answers will vary
ZnS + O2 -> ZnO + SO2
is this equation balanced/ Why or why not?
It is not balanced. There are three oxygen atoms in the products but only two in the reactants.
Give two examples of physical changes and chemical changes
Answers will vary
What is the Law of Conservation of Mass? What does this mean for chemical reactions?
Matter can never be created or destroyed, it is just rearranged. In closed systems, the mass of the reactants is equal to the mass of the products.
Why is mixing kool aid a physical change and not a chemical change?
No new substance is created; we can separate the mixture.
Describe what happened during our aluminum and copper chloride lab. What was the change? What did we see happening?
We added in solid aluminum to liquid copper chloride. The aluminum began to break down. We then saw solid copper by itself, because the aluminum reacted with the chlorine to form aluminum chloride and the copper was by itself.
S8 + 24F2 -> 8SF6
How many atoms of each element are there in the reactants? Products? Is this equation balanced?
8 sulfur and 48 fluorine on both sides, yes balanced