Which statement about an atom is correct?(1 point)
A:The proton has no charge and is found in the nucleus.
B:The neutron has no charge and is found outside of the nucleus
C:The neutron has a negative charge and is found in the nucleus
D:The electron has a negative charge and is found outside of the nucleus.
D: The electron has a negative charge and is found outside of the nucleus.
Cobalt has a mass number of 59 and an atomic number of 27. A student wants to create a model of a cobalt atom. Which statement about the model is correct?(1 point)
A:The model should show 27 protons and 27 neutrons.
B:The model should show 27 protons and 32 neutrons.
C:The model should show 59 protons and 27 neutrons.
D:The model should show 32 protons and 59 neutrons.
B: The model should show 27 protons and 32 neutrons.
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)
A:The chemical formula for lithium sulfide is LiS2.
B:A molecular model of lithium sulfide would have two spheres.
C:Both lithium and sulfur form positive ions
D:The atoms in lithium sulfide are held together by bonds.
D: The atoms in lithium sulfide are held together by bonds.
DWhat will make an atom without an electrical charge? (1 point)
Responses
A:An equal number of protons and electrons, because electrons are positively charged and protons are negatively charged.
B:An equal number of protons and electrons, because electrons are negatively charged and protons are positively charged.
C:More electrons than protons, because electrons are negatively charged and protons are positively charged, and electrons are much smaller than protons
D:An equal number of neutrons and electrons, because neutrons are positively charged and electrons are negatively charged.
B: An equal number of protons and electrons, because electrons are negatively charged and protons are positively charged.
If a substance is made of a single element, it is(1 point)
Responses
A: made of multiple types of atoms that have chemically bonded together.
B:made of one atom.
C:made of one type of atom.
D:made through chemical reactions
C: made of one type of atom.
Which element has the same number of valence electrons as bromine (Br)?
(1 point)
A:potassium (K)
B:selenium (Se)
C:krypton (Kr)
D:chlorine (Cl)
D: Chlorine (Cl)
Why are sodium (Na) and potassium (K) in the same group on the periodic table?(1 point)
A:They have similar reactivity.
B:They are both hard and brittle.
C:They have similar atomic weights.
D:They are both colorless.
A: They have similar reactivity.
A student cuts some fabric into two pieces. Is this change physical or chemical?(1 point)
A:It is a chemical change because there is no phase change.
B:It is a physical change because the process is reversible.
C:It is a chemical change because the size changes.
D:It is a physical change because there is no reaction.
D: It is a physical change because there is no reaction.
How are chemical changes different from physical changes?(1 point)
A:They involve heat.
B:They include shifts in the phase of matter
C:They are reversible.
D:They form new substances.
D: They form new substances.
How does a balanced chemical equation demonstrate the Law of Conservation of Mass?(1 point
A:it shows that all compounds remain bonded after the reaction
B:it shows that no atoms have been gained or lost during the reaction
C:it shows that only physical changes follow the Law of Conservation of Mass
D:it shows that the properties of the elements stay the same after the reaction
B: 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
A:Find the mass of an apple. Cut the apple and remove the core. Find the mass of the remaining apple.
B:Find the mass of a raw egg. Cook the egg. Find the mass of the cooked egg
C:Find the mass of a piece of ice. Let the ice melt. Find the mass of the liquid water.
D:Find the mass of a cup of water. Boil the water. Find the mass of the water that remains.
D: Find the mass of a cup of water. Boil the water. Find the mass of the water that remains.
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)
A:four
B:six
C:three
D:two
B: Six
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)
Creating models is important in understanding substances because models allow learners to visualize the basic units of a substance, the arrangement of its atoms, and how they are bonded.
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)