2.In a molecule of lithium sulfide, there are two atoms of lithium and one atom of sulfur. Which statement about lithium sulfide is correct?(1 point)
Responses
A molecular model of lithium sulfide would have two spheres.
A molecular model of lithium sulfide would have two spheres.
The chemical formula for lithium sulfide is LiS2.
The chemical formula for lithium sulfide is LiS 2 .
The atoms in lithium sulfide are held together by bonds.
The atoms in lithium sulfide are held together by bonds.
Both lithium and sulfur form positive ions.
3.Use the periodic table to answer the question.
An illustration shows the periodic table.
Which element has the same number of valence electrons as bromine (Br)?
(1 point)
Responses
chlorine (Cl)
chlorine (Cl)
krypton (Kr)
krypton (Kr)
selenium (Se)
selenium (Se)
potassium (K)
4.Why are sodium (Na) and potassium (K) in the same group on the periodic table?(1 point)
Responses
They have similar reactivity.
They have similar reactivity.
They are both hard and brittle.
They are both hard and brittle.
They have similar atomic weights.
They have similar atomic weights.
They are both colorless.
5.A student cuts some fabric into two pieces. Is this change physical or chemical?(1 point)
Responses
It is a physical change because there is no reaction.
It is a physical change because there is no reaction.
It is a chemical change because there is no phase change.
It is a chemical change because there is no phase change.
It is a physical change because the process is reversible.
It is a physical change because the process is reversible.
It is a chemical change because the size changes.
6.A student cuts some fabric into two pieces. Is this change physical or chemical?(1 point)
Responses
It is a physical change because there is no reaction.
It is a physical change because there is no reaction.
It is a chemical change because there is no phase change.
It is a chemical change because there is no phase change.
It is a physical change because the process is reversible.
It is a physical change because the process is reversible.
It is a chemical change because the size changes.
7.How does a balanced chemical equation demonstrate the Law of Conservation of Mass?(1 point)
Responses
it shows that the properties of the elements stay the same after the reaction
it shows that the properties of the elements stay the same after the reaction
it shows that all compounds remain bonded after the reaction
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 no atoms have been gained or lost during the reaction
it shows that only physical changes follow the Law of Conservation of Mass
it shows that only physical changes follow the Law of Conservation of Mass
8.Sodium reacts with chlorine to form the compound sodium chloride, or salt. The chemical formula below shows how the two elements combine into a compound.
2Na + Cl2 → 2NaCl
If the total mass of the reactants is 58.44 amu, what will be the total mass of the products?
(1 point)
Responses
29.22 amu
29.22 amu
60 amu
60 amu
58.44 amu
58.44 amu
116.88 amu
9.Which procedure could be used to demonstrate that matter is conserved during a physical change?(1 point)
Responses
Find the mass of an apple. Cut the apple and remove the core. Find the mass of the remaining apple.
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 raw egg. Cook the egg. Find the mass of the cooked egg.
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.
Find the mass of a cup of water. Boil the water. Find the mass of the water that remains.
10.One molecule of bromine (Br2) and two molecules of potassium chloride (KCl) combine in a reaction. How many atoms are in the products?(1 point)
Responses
two
two
six
six
three
three
four
11.Use the unbalanced chemical equation to answer the question.
2NaHCO3 → Na2CO3 + CO2
Which of the following can be added to the products to balance the equation?
(1 point)
Responses
O2
O 2
H2
H 2
H2O
H 2 O
CH2OH
12.The image is a model of sulfuric acid that has a chemical formula of H2SO4. In 1-2 sentences, explain why creating models, like the one shown in the image above, is important in understanding substances.
(2 points)
13.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.
(2 points)
Creating models, like the one shown in the image, is important in understanding substances because it allows us to visualize and analyze the structure and composition of the substance. By creating a model, we can better understand how the different atoms are arranged and bonded, which helps in predicting the properties and behavior of the substance.
The law that the scientist used to predict that the product of the reaction would be 15.9 grams of copper sulfide is the Law of Conservation of Mass. This law states that mass is neither created nor destroyed in a chemical reaction, so the total mass of the reactants must be equal to the total mass of the products.
i need all the anwsers
Here are the answers:
2. A molecular model of lithium sulfide would have two spheres.
3. Chlorine (Cl) has the same number of valence electrons as bromine (Br).
4. They have similar reactivity.
5. It is a physical change because there is no reaction.
6. It is a physical change because there is no reaction.
7. It shows that no atoms have been gained or lost during the reaction.
8. 58.44 amu.
9. Find the mass of a piece of ice. Let the ice melt. Find the mass of the liquid water.
10. Six atoms.
11. H2O.
12. Creating models is important in understanding substances because it allows us to visualize and analyze the structure and composition of the substance, which helps in predicting its properties and behavior.
13. The law that the scientist used to predict that the product of the reaction would be 15.9 grams of copper sulfide is the Law of Conservation of Mass. This law states that mass is neither created nor destroyed in a chemical reaction, so the total mass of the reactants must be equal to the total mass of the products.
How are chemical changes different from physical changes?(1 point)
Responses
They form new substances.
They form new substances.
They are reversible.
They are reversible.
They include shifts in the phase of matter.
They include shifts in the phase of matter.
They involve heat.
The correct answer is: They form new substances.
How does a balanced chemical equation demonstrate the Law of Conservation of Mass?(1 point)
Responses
it shows that the properties of the elements stay the same after the reaction
it shows that the properties of the elements stay the same after the reaction
it shows that all compounds remain bonded after the reaction
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 no atoms have been gained or lost during the reaction
it shows that only physical changes follow the Law of Conservation of Mass
The correct answer is: it shows that no atoms have been gained or lost during the reaction.
Sodium reacts with chlorine to form the compound sodium chloride, or salt. The chemical formula below shows how the two elements combine into a compound.
2Na + Cl2 → 2NaCl
If the total mass of the reactants is 58.44 amu, what will be the total mass of the products?
(1 point)
Responses
29.22 amu
29.22 amu
60 amu
60 amu
58.44 amu
58.44 amu
116.88 amu
116.88 amu
The correct answer is: 58.44 amu.
Which procedure could be used to demonstrate that matter is conserved during a physical change?(1 point)
Responses
Find the mass of an apple. Cut the apple and remove the core. Find the mass of the remaining apple.
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 raw egg. Cook the egg. Find the mass of the cooked egg.
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.
Find the mass of a cup of water. Boil the water. Find the mass of the water that remains.