Chemical Changes
Chemical Equations & Reactions
Energy & Chemical Reactions
Addition, Decomposition, & Combustion Reactions
Chemical Reactions Miscellaneous
100
Bubbling may be evidence of a chemical reaction, indicating formation of a new gas. Name three other observations that may be evidence of chemical change and what each indicates.
Turning cloudy may indicate a new solid is forming. A change in temperature may indicate chemical bonds are changing. A color change may indicate a new substance is forming.
100
What in a chemical equation shows the direction of the reaction?
The arrow indicates the direction, from reactants to products.
100
What is it called when elements react with Oxygen and give off energy?
Combustion!
100
What kind of reaction is this, 2H2O(l) ---------> 2H2(g)+ O2(g) and what must be added to make it happen?
It is a decomposition reaction, and it requires electricity to happen.
100
What notation identifies the phase of each substance in a chemical reaction?
(g) gas, (s) solid, (l) liquid, (aq) aqueous
200
These are broken and reformed in a chemical reaction.
What are chemical bonds.
200
Why are you not allowed to change a subscript when balancing a chemical equation?
The subscript indicates the number of atoms per molecule. A change in the subscript would make the formula represents an entirely different compound.
200
What is an example of an endothermic reaction that sustains life on Earth?
Photosynthesis.
200
Hydrocarbons are composed of what atoms?
Hydrogen and carbon.
200
What is an example of a chemical reaction that gives off energy in the form of heat and light?
Burning.
300
Ice melting is an example of what kind of change? Explain.
Ice melting is an example of a physical change. The substance (water) changes state, from solid to liquid, but it remains the same substance.
300
What does it mean to say that mass is conserved in a chemical reaction?
Matter changes when chemical reactions happen, but matter is never lost. No new atoms are created!
300
What role does activation energy play at the start of a chemical reaction?
Activation energy breaks bonds, making atoms available to form new bonds.
300
Polyethylene is a long chain polymer made up of what?
Bonded ethylene monomers.
300
Aqueous calcium chloride produces what kind of reaction, and how does that suit its safety-related application ?
Calcium chloride in water produces an exothermic reaction, making the chemical useful as a de-icer.
400
What is the name for substances that combine and change in a chemical reaction?
Reactants!
400
Which of the following reactions is balanced? 4KMnO4 ---------> 2K2O + 4MnO + 4O2 2N2O5 + NO -----> 4NO2 Cl2 + 2Br --------> 2Cl + Br2
Cl2 + 2Br --------> 2Cl + Br2
400
What does a spark, a flame, or heat provide to some chemical reactions?
Activation energy.
400
How are the properties of a polymer affected by cross linking?
Cross linked polymer chains form a stronger interlocking structure, and a more durable polymer.
400
After seeing how calcium carbonate in egg shell decomposes in vinegar, what kind of conditions do you think would disrupt shell formation in marine organisms?
Acidic conditions, as for example, could result from high levels of dissolved Carbon dioxide.
500
Is dissolving sugar in water a chemical change or a physical change?
A physical change.
500
If you compare the mass of baking soda and vinegar before and after being mixed in an open beaker, would you expect it to be the same, or different? Why?
You would expect the mass to decrease because of escaped gas.
500
If the energy released by the formation of products is greater than the activation energy, what kind of reaction is it?
An exothermic reaction
500
What is evidence that in the real world, combustion reactions are never perfect?
Fuel never burns completely and conditions in the atmosphere always result in products in addition to carbon dioxide and water (for example, carbon monoxide, nitrogen oxides, and sulfuric acid, )
500
What is burning when a candle burns?
vaporized candle wax
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