Why are sodium (Na) and potassium (K) in the same group on the periodic table? (1 point)
• They are both hard and brittle.
• They have similar reactivity.
O They have similar atomic weights.
• They are both colorless.
25 answers
• They have similar reactivity.
A student cuts some fabric into two pieces. Is this change physical or chemical? (1 point)
• It is a physical change because there is no reaction.
O It is a chemical change because there is no phase change.
• It is a chemical change because the size changes.
• It is a physical change because the process is reversible.
• It is a physical change because there is no reaction.
O It is a chemical change because there is no phase change.
• It is a chemical change because the size changes.
• It is a physical change because the process is reversible.
• It is a physical change because the process is reversible.
How are chemical changes different from physical changes? (1 point)
• They are reversible.
• They involve heat.
• They form new substances.
O They include shifts in the phase of matter.
• They are reversible.
• They involve heat.
• They form new substances.
O They include shifts in the phase of matter.
• They form new substances.
How does a balanced chemical equation demonstrate the Law of Conservation of Mass? (1 point)
• it shows that only physical changes follow the Law of Conservation of Mass
• it shows that all compounds remain bonded after the reaction
• it shows that no atoms have been gained or lost during the reaction
• it shows that the properties of the elements stay the same after the reaction
• it shows that only physical changes follow the Law of Conservation of Mass
• it shows that all compounds remain bonded after the reaction
• it shows that no atoms have been gained or lost during the reaction
• it shows that the properties of the elements stay the same after the reaction
• it shows that no atoms have been gained or lost during the reaction
Which procedure could be used to demonstrate that matter is conserved during a physical change? (1 point)
• Find the mass of an apple. Cut the apple and remove the core. Find the mass of the remaining apple.
• Find the mass of a cup of water. Boil the water. Find the mass of the water that remains.
• Find the mass of a raw egg. Cook the egg. Find the mass of the cooked egg.
• Find the mass of a piece of ice. Let the ice melt. Find the mass of the liquid water.
• Find the mass of an apple. Cut the apple and remove the core. Find the mass of the remaining apple.
• Find the mass of a cup of water. Boil the water. Find the mass of the water that remains.
• Find the mass of a raw egg. Cook the egg. Find the mass of the cooked egg.
• Find the mass of a piece of ice. Let the ice melt. Find the mass of the liquid water.
• Find the mass of a piece of ice. Let the ice melt. Find the mass of the liquid water.
One molecule of bromine (Br) and two molecules of potassium chloride (KCI) combine in a reaction. How many atoms are in the products? (1 point)
• three
• two
O six
• four
• three
• two
O six
• four
• four
Use the unbalanced chemical equation to answer the question.
2NaHCO3 - Na2GO3 + CO2
Which of the following can be added to the products to balance the equation?
(1 point)
• CH2OH
0 O2
0 H2
0 H2O
2NaHCO3 - Na2GO3 + CO2
Which of the following can be added to the products to balance the equation?
(1 point)
• CH2OH
0 O2
0 H2
0 H2O
0 H2O
Use the unbalanced chemical equation to answer the question.
2NaHCO3 - Na2GO3 + CO2
Which of the following can be added to the products to balance the equation?
(1 point)
A. CH2OH
B. O2
C. H2
D. H2O
2NaHCO3 - Na2GO3 + CO2
Which of the following can be added to the products to balance the equation?
(1 point)
A. CH2OH
B. O2
C. H2
D. H2O
D. H2O
Use the chemical equation to complete the activity.
2Cu + S - > Cu2S
Copper (Cu) reacts with sulfur (S) to form copper sulfide as shown in the equation. A scientist adds 12.7 grams of Cu to 3.2 grams of S to start the reaction. In this reaction, all of the copper and all of the sulfur react. Before running the experiment, the scientist expected the products of the reaction will be a total of 15.9 grams of copper sulfide (Cu2S). In 1-2 sentences, explain the law that the scientist used to predict that the product of the reaction would be 15.9 grams of copper sulfide.
2Cu + S - > Cu2S
Copper (Cu) reacts with sulfur (S) to form copper sulfide as shown in the equation. A scientist adds 12.7 grams of Cu to 3.2 grams of S to start the reaction. In this reaction, all of the copper and all of the sulfur react. Before running the experiment, the scientist expected the products of the reaction will be a total of 15.9 grams of copper sulfide (Cu2S). In 1-2 sentences, explain the law that the scientist used to predict that the product of the reaction would be 15.9 grams of copper sulfide.
The scientist used the Law of Conservation of Mass to predict that the product of the reaction would be 15.9 grams of copper sulfide. According to this law, the total mass of the reactants must be equal to the total mass of the products in a chemical reaction.
Write it differently
Based on the Law of Conservation of Mass, the scientist predicted that the total mass of the copper sulfide product would be 15.9 grams. This law states that in a chemical reaction, the mass of the reactants must be equal to the mass of the products.
Write it another way
By applying the Law of Conservation of Mass, the scientist was able to anticipate that the resulting mass of the copper sulfide product would be 15.9 grams. This fundamental law affirms that in a chemical reaction, the total mass of the reactants remains the same as the total mass of the products.
Write it a another way make sure its not plagiarism
Drawing upon the Law of Conservation of Mass, the scientist made a reasoned projection that the combined mass of the copper sulfide product would amount to 15.9 grams. This law dictates that, in a chemical reaction, the sum of the masses of the reactants must equate to the sum of the masses of the products, ensuring the overall mass remains constant throughout the process.
Which element has the same number of valence electrons as bromine (Br)?
(1 point)
• krypton (Kr)
• potassium (K)
O selenium (Se)
• chlorine (CI)
(1 point)
• krypton (Kr)
• potassium (K)
O selenium (Se)
• chlorine (CI)
• chlorine (CI)
1 answer