Chemical and physical changes
How to identify a chemical change
Chemical reactions
Chemical equations
100
Is cutting a paper a physical or a chemical change?
It's a physical change.
100

What change would you see when an apple is rotting?

You could see that the color is changing from yellow to brown.

100
Decide which are the reactants and which are the products in the following reaction: Hydrogen reacts with nitrogen to produce ammonia.
The reactants are hydrogen and nitrogen and the product is ammonia.
100
True or false: The formulas of the reactants appear after the arrow.
False: The formulas of the reactants appear before the arrow.
200
Is melting water a physical or a chemical change?
It's a physical change.
200

What change would occur when an egg is rotting?

You can appreciate a new smell (it smells like sulfur).

200
Decide which are the reactants and which are the products in the following reaction: Lithium reacts with water to produce hydrogen and lithium hydroxide.
Reactants: Lithium and water. Products: Hydrogen and lithium hydroxide.
200
What do we use to separate the formula of one reactant from the formula of other reactant?
The formulas are separated with a plus sign.
300
Is mixing vinegar and bicarbonate a physical or a chemical change?
It's a chemical change
300

What change would occur when you are burning paper?

You can see that the paper is being transformed into smoke and ashes.

300
What is the difference between a chemical reaction and a chemical equation?
A chemical equation is the representation of a chemical reaction.
300

What 2 products indicate that a COMBUSTION reaction has occured?

CO2 and H20

400
Is mixing salt and water a physical or a chemical change?
It's a physical change
400

What change would occur when a precipitate happens?

You can see a solid forming from the reaction of 2 liquids

400
What is a chemical reaction?
A chemical reaction is a process in which one or more substances, the reactants, are converted to one or more different substances, the products.
400
Read the following chemcial equation: CH4 + 2 O2 --> CO2 + 2 H2O
One molecule of methane reacts with two molecules of oxygen to produce one molecule of carbon dioxide and two molecules of water.
500
What is the main difference between a physical and a chemical change?
Physical changes do not produce new substances while chemical changes produce new substances.
500

Name 5 indicators of chemical changes.

1. Production of an odor. 2. Change in color. 3. Change in temperature. 4. Emission of gases. 5. Formation of a solid.

500
Why are new substances formed in a chemical reaction?
Because the atoms which form the reactants reorder and join in a different way.
500
Read the following chemical equation: 2 Li + Cl2 --> 2 LiCl
Two atoms of lithium react with one molecule of chlorine to produce two molecules of lithium chloride.
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