Understanding the Law of Conservation of Mass in Reactions

School

Lennard High School**We aren't endorsed by this school

Course

SCIENCE PYSICAL03

Subject

Chemistry

Date

Dec 12, 2024

Pages

Uploaded by DrMink4677

End of Unit B Test Review1. State the Law of Conservation of Mass.The Law of Conservation of Mass states that mass in an isolated system is neither created nor destroyed by chemical reactions or physical transformations. The mass of the reactants in a chemical reaction is equal to the mass of the products. Essentially, the total mass remains constant throughout the process.2. Practice: Use the following chemical reaction to answer the questions below:a. How many molecules of copper sulfate are in the reaction?molecules of copper sulfate (CuSO₄).b. How many different types of elements are used?different elements: Aluminum (Al), Copper (Cu), Sulfur (S), and Oxygen (O).c. What is the total number of atoms in the reactants?20 atoms total in the reactants.d. What is the total number of atoms in the products?20 atoms total in the products.e. Circle the reactants.The reactants are 2Al+3CuSO42f. If there are 30 g of reactants, how many grams of product will there be?30 grams of products, because mass is conserved.a.How many molecules of sulfuric acid are in the reaction?b.1 molecule of sulfuric acid (H₂SO₄).c.How many different types of elements are used?d.4 types: Zinc (Zn), Hydrogen (H), Sulfur (S), and Oxygen (O).e.What is the total number of atoms in the reactants?f.8 atoms.g.What is the total number of atoms in the products?h.8 atoms.i.Circle the reactants.j.The reactants are Zinc (Zn) and Sulfuric acid (H₂SO₄).k.Why did the mass change?l.The mass changed because hydrogen gas (H₂) was released and escaped from the open test tube, which reduced the total mass inside the test tube.

4. List the following as either chemical properties or physical properties:Physical Properties:ColorElectrical conductivityFlexibilityDensityLusterMiscibility (the ability of liquids to mix)Boiling PointMelting PointChemical Properties:Reactivity (how a substance interacts with other substances)Flammability (the ability to catch fire)5. List the following as either chemical or physical changes:Chemical Changes:Rusting (iron reacts with oxygen to form rust)Tarnishing (silver reacts with sulfur compounds to form tarnish)Burning (a substance reacts with oxygen to produce heat and light, forming new substances)Color Change (if it's due to a chemical reaction)Gas is formed (indicating a chemical reaction)Light is released (often a sign of a chemical reaction)Temperature increases (if it's due to a chemical reaction)Physical Changes:Evaporation (liquid water turns into vapor without changing its chemical composition)Boiling (liquid to gas phase change without chemical change)Folding (changing the shape but not the chemical identity)Melting (solid to liquid phase change without chemical change)Slicing (cutting into smaller pieces without changing the chemical composition)

6. What are some ways to increase the rate of a reaction?Increase Temperature: Higher temperatures provide reactant molecules with more energy, causing them to move fasterand collide more often with enough energy to react.7. Lab on Growing Tomato Plants:a. Independent variable:Type of liquid used.b. Dependent variable:Growth of the tomato plants.c. Constants:Type of tomato plants, amount of liquid, watering frequency, sunlight, soil type, temperature.d. Lab Setup:Use multiple groups of plants, each with a different liquid.Keep all other conditions the same for all groups.Record plant growth over time.e. Before Publishing Results:Analyze data, repeat the experiment for consistency, compare with other research, write a report, and get peer-reviewed.8. Elements Similar to Chlorine:Fluorine (F), Bromine (Br), Iodine (I), and Astatine (At).

9. Which element is in Period 5, Group 2?Strontium (Sr).10. How did the periodic table change from Mendeleev's to today's?Mendeleev: Arranged by atomic mass.Today: Arranged by atomic number, includes more elements and new groups.11. Roles of scientists vs. lawmakers when an unknown substance is found outside a factory:Scientists: Identify the substance, assess impacts, suggest disposal.Lawmakers: Use data for policies, enforce regulations, draft new laws.12. Place the correct term (homogenous, heterogeneous, element, compound) in the boxes below:

Homogeneous: Uniform mixture (e.g., saltwater).Heterogeneous: Non-uniform mixture (e.g., salad).Element: Pure substance with one type of atom (e.g., gold).Compound: Pure substance with two or more different elements chemically combined (e.g., water).13. List the following as either elements or compounds:a. Water (H₂O) - Compoundb. Copper (Cu) - Elementc. Hydrogen gas (H₂) - Elementd. Sodium Chloride (NaCl) - Compound

e. Glucose (C₆H₁₂O₆) - Compound14. Fill out the following table to summarize the information on the three subatomic particles:Subatomic ParticleChargeMassProton+11 atomic mass unit Neutron01 atomic mass unit Electron-11/1836 atomic mass unit15. Summarize the changes in the atomic theory from Dalton to Thompson to Rutherford and why these changes occurred.Dalton:Theory: Atoms are indivisible particles and the building blocks of matter.Changes: First modern description of atoms.Why: Based on chemical reaction observations.Thomson:Theory: Discovered electrons; proposed "plum pudding" model (electrons in a positive "pudding").Changes: Showed atoms are divisible and have subatomic particles.Why: Cathode ray experiments revealed internal atomic structure.Rutherford:Theory: Proposed the nuclear model (dense, positive nucleus with electrons around it).Changes: Replaced the plum pudding model.WhyGold foil experiment showed a dense nucleus.