Here's a comprehensive breakdown of your questions, along with the corresponding answers based on the lessons you've described.
Lesson 1: Physical vs. Chemical Change
Question: In a physical change, a substance’s _____ changes but it remains the ______ substance.
Answer: appearance; same
Question: When a substance undergoes a chemical change, what will its atoms do?
Answer: The atoms will rearrange to form new substances.
Question: What are 4 signs of a chemical change?
Answer: 1) Color change 2) Production of gas 3) Formation of a precipitate 4) Change in temperature
Question: The 4 signs aren’t completely reliable, so what is the only real way to determine if a chemical change occurred?
Answer: Performing a chemical analysis to identify changes in composition.
Lesson 2: Chemical Reactions
Question: What does the Law of Conservation of Mass state?
Answer: The mass of reactants is equal to the mass of the products in a chemical reaction; mass cannot be created or destroyed.
Question: If the reactants of a chemical reaction have a total mass of 36g, what will be the total mass of the products? Why?
Answer: The total mass of the products will also be 36g because of the Law of Conservation of Mass.
Question: What are the three major tenets to the Law of Conservation of Mass?
Answer: 1) Matter is not created or destroyed in a reaction. 2) Atoms are only rearranged. 3) The initial mass of the reactants is equal to the mass of the products.
Question: Write this chemical equation in sentence form:
Answer: Four iron molecules react with three oxygen molecules to produce two iron(III) oxide molecules.
Question: Explain the difference between a coefficient and a subscript in a chemical equation.
Answer: The coefficient indicates how many molecules or atoms are present, while the subscript indicates how many atoms of an element are in a single molecule.
Question: Complete question 2 on page 9 of the lesson using the table provided below:
(You need to fill out the table provided, but here's an outline you can use)
-
Reactants:
- Aluminum (Al)
- Coefficient: ___
- Subscript: ___
- Number of Atoms: ___
- Oxygen (O)
- Coefficient: ___
- Subscript: ___
- Number of Atoms: ___
- Aluminum (Al)
-
Products:
- Aluminum (Al)
- Coefficient: ___
- Subscript: ___
- Number of Atoms: ___
- Oxygen (O)
- Coefficient: ___
- Subscript: ___
- Number of Atoms: ___
- Aluminum (Al)
(Specific values will depend on the equation provided.)
Lesson 3: Acids and Bases
Question: Where on the pH scale are the strongest acids located? Where are the strongest bases?
Answer: The strongest acids are located at the low end of the pH scale (0-3), while the strongest bases are at the high end (11-14).
Question: The pH scale is actually measuring the amount of hydronium ions and hydroxide ions. What is the formula for each ion?
Answer: Hydronium ion: \( H_3O^+ \); Hydroxide ion: \( OH^- \)
Question: If a substance has more hydronium ions than hydroxide ions when dissolved in water, then that substance must be a(n) (acid or base)?
Answer: Acid
Question: Bases still contain some hydronium ions, though far less than acids. Which base would have more hydronium ions; baking soda (pH 8) or ammonia (pH 11)?
Answer: Baking soda (pH 8) has more hydronium ions than ammonia (pH 11).
Question: Acids and Bases can react in a neutralization reaction. What are always the products in a neutralization reaction?
Answer: A salt and water.
Lesson 4: Naming Compounds
Question: For the given non-metal anion, give the compound ion name:
Nitrogen: Nitride
Sulphur: Sulfide
Fluorine: Fluoride
Chlorine: Chloride
Question: How do you know what charge an ion of a certain element will carry?
Answer: The charge of an ion is determined by the number of electrons lost or gained to achieve a stable electron configuration, typically resembling that of the nearest noble gas.
Question: Write formulas for the ionic compounds below.
-
Calcium iodide
- Positive ion: \( Ca^{2+} \)
- Negative ion: \( I^- \)
- Formula of the compound: \( CaI_2 \)
-
Potassium Bromide
- Positive ion: \( K^+ \)
- Negative ion: \( Br^- \)
- Formula of the compound: \( KBr \)
-
Magnesium Nitride
- Positive ion: \( Mg^{2+} \)
- Negative ion: \( N^{3-} \)
- Formula of the compound: \( Mg_3N_2 \)
Question: How do you know which nonmetal element to put first in the name of a covalent compound?
Answer: The nonmetal with the lower group number on the periodic table is typically placed first in the name of a covalent compound; if they are in the same group, the one with the higher period number is placed first.
Fill out the table below for Covalent Compounds
-
Formula: NO
Name: Nitric oxide -
Formula: \( S_2Cl_2 \)
Name: Disulfur dichloride -
Formula: \( N_2O_7 \)
Name: Dinitrogen heptoxide
Lesson 5: Balance of Atoms
Question: What happens to the atoms in a chemical reaction?
Answer: Atoms are rearranged to form new substances; they do not disappear or change into different atoms.
Question: What does it mean to say that matter is conserved in a chemical reaction? Use the words REACTANTS and PRODUCTS in your answer.
Answer: Matter is conserved in a chemical reaction, meaning that the total mass of the REACTANTS before the reaction is equal to the total mass of the PRODUCTS formed after the reaction.
Question: A 50 gram nail is left outside. In 1 week it is rusty and now has a mass of 55 grams. How can this be if matter cannot be created or destroyed?
Answer: The increase in mass is due to the nail reacting with oxygen in the air and moisture, forming rust and incorporating additional material from the environment.
Lesson 6: Law of Conservation of Matter
Question: State the Law of Conservation of Matter in your own words.
Answer: The total amount of matter remains the same during a chemical reaction; it cannot be created or destroyed.
Question: Fill in the blanks to complete this statement:
Answer: According to the Law of Conservation of Matter, all the atoms in the reactants will still be present in the products — no atoms will disappear and none will appear.
Question: If a reaction occurs between 12 g of carbon and 32 g of oxygen, what will be the mass of the carbon dioxide product?
Answer: The mass of the carbon dioxide product will be 44 g (12 g of carbon + 32 g of oxygen).
Question: Does this diagram follow the law of conservation of matter? Explain your answer:
Answer: (Depending on the specific diagram provided) If the number of atoms in the reactants does not equal the number in the products, it does not follow the law of conservation of matter.
Count of atoms in the combustion of methane:
Reactants count:
- C = ___ (1)
- H = ___ (4)
- O = ___ (2)
Products count:
- C = ___ (1)
- H = ___ (2)
- O = ___ (2)
Does this demonstrate the law of conservation of matter?
Answer: Yes, because the number of each type of atom in the reactants equals the number of each type in the products.
Lesson 7 & 8: Reaction Rates Portfolio
(Instructions refer to a separate portfolio task; continue with virtual experiments as specified.)
Test Essay Questions
Test question number 1:
Question: Write the chemical equation in sentence form.
Answer: Four iron atoms react with three molecules of oxygen to form two molecules of iron(III) oxide.
Question: A scientist adds 15.4 grams of Fe to 3.6 grams of O2 to start the reaction. What should be the mass of the products?
Answer: The total mass of the products should be 19 grams (15.4g Fe + 3.6g O2).
Question: Does this equation demonstrate the Law of Conservation of Matter? Explain specifically how you know.
Answer: Yes, because the total mass of the reactants (19g) is equal to the total mass of the products, showing that matter is neither created nor destroyed in the reaction.
This information should provide a solid foundation for your test preparation. Good luck!
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