Physical and Chemical Reactions

A chemical change is different than a physical change because in a chemical change...

• Chemicals are used

• Molecules do not physically touch

• A new substance is formed and in a physical change no new substance is formed

• The change can be seen but in a physical change it cannot

Tags

NGSS.MS-PS1-2

In a chemical reaction...

• The atoms of the reactants always stay together to form the products

• chemical bonds between atoms are broken and new chemical bonds are formed.

• New atoms are formed which combine to make the products

• Some atoms disappear while others appear to form the products

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

In a chemical reaction, mass is conserved. This means that

• The mass of the products stays the same during a chemical reaction

• The mass of the products is always twice the mass of the reactants

• The mass of the reactants stays the same during a chemical reaction

• The type and number of atoms in the reactants equals the type and number of atoms in the products

Tags

NGSS.MS-PS1-5

If the reactants on the left side of a chemical equation are C3H8 + 5O2, the products in a balanced equation could be

• 2CO2 + 3H2O

• 3CO + 4H2O

• 3CO2 + 4H2O

• 4CO2 + 3H2O

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

The law of conservation of mass

• applies to physical changes.

• applies to chemical changes

• applies to both chemical and physical changes

Tags

NGSS.MS-PS1-5

In the chemical reaction CH4 + 2O2 → CO2 + 2H2O, there are reactants on the left of the equation and products on the right. If you count the atoms in the reactants, there are

• 4 carbon atoms, 4 hydrogen atoms, and 2 oxygen atoms

• 1 carbon atom, 4 hydrogen atoms, and 2 oxygen atoms

• 1 carbon atom, 4 hydrogen atoms, and 4 oxygen atoms

• 4 carbon atoms, 4 hydrogen atoms, and 4 oxygen atoms

Tags

NGSS.MS-PS1-1

NGSS.MS-PS1-5

_________ is (are) made of more than one atom.

• A molecule
• Protons
• Neutrons
• An element

Tags

NGSS.MS-PS1-1

________ result(s) in no new substances.

• A physical change
• A chemical change
• Physical and chemical changes
• None of the above

Which is an example of a physical change?

• Burning wood
• Freezing water
• Rust on a car
• Cooking food

Tags

NGSS.MS-PS1-4

Which is an example of a chemical change?

• Burning wood

• vinegar and baking soda reacting to form carbon dioxide.

• Cooking food

• All of the above

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5