Chemical Reactions

Which of the following is a sign that a chemical reaction has occurred?

• Melting ice

• Dissolving sugar

• Color change

• Breaking glass

What is an atom?

• A mixture of elements

• The smallest unit of a chemical element

• A compound of molecules

• A group of ions

Which of these is a compound?

• H

• H₂

• O₂

• H₂O

What distinguishes a mixture from a compound?

• Mixtures cannot be separated

• Mixtures involve chemical bonding

• Mixtures retain individual substance properties

• Mixtures are always gases

What happens to chemical bonds during a chemical reaction?

• Bonds are only formed

• Bonds are only broken

• Bonds are broken and formed

• Bonds are unchanged

What does the rate of a chemical reaction describe?

• The energy used

• The time it takes to stop

• How fast the reaction occurs

• The color of products

Increasing temperature affects particle motion by:

• Slowing particles down

• Reducing collisions

• Increasing kinetic energy

• Decreasing reaction rate

For a reaction to occur, particles must:

• Be frozen

• Move in circles

• Collide with enough energy

• Have opposite charges

What effect does higher concentration have on the rate of reaction?

• No effect

• Slows it down

• Speeds it up

• Changes the color

Smaller particle size leads to:

• Slower reaction rate

• More surface area for collisions

• Less product

• Increased mass