Use the information in this box to answer questions 1 & 2:
Wilfred made observations as he watched a white candle burn.
2 points
2
Question 1
1.
Which of Wilfred’s observations shows that a chemical reaction has taken place? (2 pts)
The candle is white and made of wax and a wick.
The wax starts to melt.
Black smoke is given off; hot gases are rising.
Time passes one minute at a time
2 points
2
Question 2
2.
Why does this observation show a chemical reaction has taken place? (2 pts)
It shows that the candle has changed from one state to another
It shows that the candle did not change state
It shows that a new substance was created
It shows that no new substances were created
2 points
2
Question 3
3.
Which of the following models could show what happened to the molecules of the candle including the oxygen in the air during the chemical reaction? (2 pts)
CFS:
How many atoms before the reaction?
How many atoms after the reaction?
Is there a new substance (with new molecules/groups of atoms)?
2 points
2
Question 4
4.
This is a picture of the substances in a chemical reaction before and after the reaction. (2 pts)
Using what you have learned about chemical reactions, choose the answer that best explains what happens to the weight of the substances after a chemical reaction occurs.
A. The weight of the substances have changed after a chemical reaction occurs, because they have gone through a physical change, which would change the weight of the substances.
B. The weight of the substances before and after a chemical reaction stay the same, because even though the substances may change form, the weight of each atom does not change.
C. The weight of the substances have changed, because the atoms of the substance have changed. The change in atoms will cause the weight of the substances to change after a chemical reaction.
D. The weight of the substances do not change, because they are still the same substances which went through a chemical reaction.