Name:______date:______period:______(3)

Science 8: Ch 9.1 Forming New Substances (pages 256-261)

Key Concept
During chemical reactions, atoms ______to form new substances that have ______properties than the original substances have.
What happens when chlorophyll breaks down into new substances?
Define chemical reaction.
What forms when you mix water with baking soda (Figure 1)?
What are four examples a chemical reaction has taken place (Figure 2)? / 1.
2.
3.
4.
Define precipitate
Do all good signals guarantee a chemical reaction is happening?
What is an example of a physical change than may look like a chemical reaction is occurring?
What is the most important sign a chemical reaction has taken place?
Looking at Figure 3 on page 258, how can you tell a chemical reaction has taken place. Compare the original substances by the new substance.
Define chemical bond
For a chemical reaction to take place, what has to happen to the chemical bonds?
For new substances to form from a chemical reaction, what must first happen to the chemical bonds of the original substance?
How can chemical bonds in molecules break?
For new bonds to forms, What happens to the atoms?

Looking at Figure 4, draw and label how the diatomic molecules of hydrogen and chlorine react to produce hydrogen chloride.

What is a physical property of the diatomic molecule chlorine?
What is a physical property if the diatomic molecule hydrogen?
When chlorine gas and hydrogen gas react, what happens to the bonds between the hydrogen atoms and the chlorine atoms?
What new bond is formed (from the previous question)?
What is a physical property if hydrogen chloride?
What is a part of all chemical reactions?
What is the energy used for?
When new bonds form in the final substances, what happens to the energy? Is it absorbed or released?
How can you decide if energy is absorbed or released in an overall reaction?
Define exothermic reaction
What does “exo” mean?
What does “thermic” mean?
What will happen to nearby matter if an exothermic reaction occurs?
How does the nearby matter get warmer?
What are two examples of an exothermic reaction? / 1.
2.
Define endothermic reaction
What does “endo” mean?
Where does the energy absorbed in an endothermic reaction come from?
What is an example of an endothermic reaction?
Define the law of conservation of energy
What can energy do?
Can energy be transferred?
The energy released from an exothermic reaction was first stored where?
The energy taken in during endothermic reactions was stored where?
What is the difference in energy before and after a chemical reaction?