Which element has the same number of valence electrons as bromine (Br)?
(1 point)
krypton (Kr)
potassium (K)
chlorine (Cl)
selenium (Se)
Six.
burning wood
It is a physical change because there is no reaction.
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, mass is conserved in a chemical reaction, meaning that the total mass of the reactants is equal to the total mass of the products. By combining the masses of the copper and sulfur, the scientist could determine the expected mass of the copper sulfide product.
Sure! Let me simplify my response for a 7th grader level:
The scientist used a rule called the Law of Conservation of Mass to figure out that the product of the reaction would be 15.9 grams of copper sulfide. This rule says that during a chemical reaction, the total mass of the stuff you start with (reactants) is the same as the total mass of the stuff you end up with (products). By adding up the masses of the copper and sulfur, the scientist could guess how much copper sulfide would be made.
Of course! Here's a simpler explanation:
The scientist used a rule that says when you mix different things together, you can't make or lose any stuff. So, if you start with some copper and some sulfur, you'll end up with copper sulfide, and you won't have more or less stuff than before. By adding up the weights of the copper and sulfur, the scientist guessed how much copper sulfide would be made.
Chlorine (Cl) has the same number of valence electrons as bromine (Br).
Why are sodium (Na) and potassium (K) in the same group on the periodic table?(1 point)
Responses
They are both colorless.
They have similar reactivity.
They have similar atomic weights.
They are both hard and brittle.
They have similar reactivity.
A student cuts some fabric into two pieces. Is this change physical or chemical?(1 point)
Responses
It is a physical change because the process is reversible.
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 the size changes.