Chemical reactions

Which of the following describes what happens in a chemical reaction?

• Atoms of the molecules in the reactants are rearranged to make new substances.

• The atoms in the reactants stay together to make the products.

• New atoms are formed that are put together to make new substances.

• Some of the original atoms disappear and others are added to make products.

What are the products in the following reaction?

 $CH_4+2O_2\rightarrow CO_2+2H_{2_{ }}O$  

•  $H_{2_{ }}O$  and $CO_2$  

•  $CH_4\ and\ O_2$  

•  $CO_{2\ }and\ \ O_2$  

•  $CH_{4\ }and\ H_2O$  

How many atoms of oxygen are present in one molecule of C₆H₁₂O₆?

• 6

• 12

• 18

• 24

Which of the following describe a decomposition reaction? Select all that apply.

• In a decomposition reaction, one substance breaks down into two or more substances.

• The general equation for a decomposition reaction is AB→A+B

• The general equation for a decomposition reaction is A+B→AB

  .

• A decomposition reaction is the opposite of a synthesis reaction.

Which statement is not true of chemical reactions?

• All chemical reactions are easily seen.

• Some chemical reactions are fast, but some are slow.

• Chemical reactions involve breaking chemical bonds, rearranging atoms, and forming new substances.

• During a chemical reaction, the number of atoms will remain the same before and after the reaction.

Which are signs of a chemical reaction? Select all that apply.

• change in temperature

• production of a gas

• production of a solid

• change in shape

Which interaction is a chemical reaction resulting in a visible production of a gas?

• mixing vinegar and baking soda

• water turning into ice cubes

• the cooking of an egg

• a rotting banana

Which type of chemical change is produced when a match is lit?

• change in temperature

• change in color

• production of a gas

• production of a solid

When do chemical reactions occur?

• when the particles of reactants collide

• when the particles of reactants dissolve

• when more particles are added

• when the particles of reactants are heated

Which is an example of an endothermic reaction?

• cooking an egg

• combustion of a fuel

• a candle flame

• burning of coal