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Demo Assessment: Energy in a Chemical Reaction

Last updated about 6 years ago

10 questions

Note from the author:

Energy in Chemical Reactions using Polyurethane A + B as a demo and having students apply their learning to explain what is happening.

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Question 10

10.

During chemical reactions the bonds between atoms break and new bonds form. Energy must be absorbed to break a bond, so breaking bonds is endothermic. Making new bonds is exothermic because energy is released.

Looking at the image above, what kind of reaction is occurring and how do you know?

Endothermic and Exothermic because there are multiple molecules in the reactants which broke down and formed new bonds creating different molecules in the product.

Endothermic because the reactant started off as one molecule which was broken down into two separate molecules and breaking bonds is endothermic since it requires energy to be absorbed.

Question 1

1.

Observations of Poly. A before:

Question 2

2.

Observations of Poly. B before:

Question 3

3.

Question 4

4.

What type of a chemical reaction is this?

Endothermic

Exothermic

It is NOT a chemical reaction, rather it's a physical change

There is not enough information to answer this.

Question 5

5.

How do you know it's that type of a chemical reaction?

Because as a result of the reactants mixing, NEW substances formed that weren't there before.

Because as a result of the reactants mixing, NOTHING changed.

Because as a result of the reactants mixing, new substances formed that weren't there before and an INCREASE in temperature occurred.

Question 6

6.

Using Arrows, show what is happening to the energy in this reaction (where it came from and where it's going).

Question 7

7.

The word energy should be placed in which part of this chemical equation?

The Reactant Side because it is an endothermic reaction

The Product side because it is an endothermic reaction

The Reactant Side because it is an exothermic reaction

The Product side because it is an exothermic reaction

Question 8

8.

Which of the statement below is true:

All chemical reactions involve the flow of energy.

All chemical reactions involve the addition of sunlight

All chemical reactions require the addition of atoms in order to produce a stable product

All chemical reactions must have Oxygen in order to react.

Question 9

9.

During one of our labs we combined ammonium chloride with water which resulted in a loss of thermal energy (heat). What kind of a reaction occurred?

Endothermic

Exothermic

No reaction occurred

Both reactions occurred simultaneously

Exothermic because the reactant started off as one molecule which was broken down into two separate molecules and breaking bonds requires energy to be absorbed in order to do so.

Exothermic because the reactants had to form more bonds  to create multiple molecules  which releases energy.

What evidence can be observed that a chemical reaction has occured? Select ALL that apply (4).

a loss of mass

the substance solidified

the substance remained unchanged

the substance became watery

production of gas

Increase in temperature

decrease in temperature

the substance gained mass in total

the substance turned a cream color or yellowish/off-white

Because as a result of the reactants mixing, new substances formed that weren't there before and a DECREASE in temperature occurred.