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

In a chemical reaction...

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

• The atoms of the reactants unbond, rearrange, and then rebond to form the products

• New atoms are formed which combine to make the products

• Some atoms disappear while others multiply 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

If two substances react and the temperature of the mixture increases, the reaction is

• Not one that produces anything new

• Exothermic

• One that needs a catalyst

• Endothermic

Tags

NGSS.MS-PS1-4

If two substances react and the temperature of the mixture decreases, the reaction is

• Endothermic

• Never going to happen unless it is heated

• Exothermic

• one that causes atoms to be destroyed

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

The law of conservation of mass states

• matter can not be created or destroyed

• matter can be created and destroyed

• matter can be changed and created

• matter can be rearranged and destroyed

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

Increasing the amount of reactants may increase the amount of

• atoms

• matter

• molecules

• products

Tags

NGSS.MS-PS1-5

What is a sign of a physical change?

• odor produced

• change in state of matter

• light

• temperature change

Tags

NGSS.MS-PS1-4