Properties & Substances
What is a property of a substance?
A characteristic that can be observed or measured, such as color, smell, texture, melting point, or hardness.
What are substances made of?
Atoms.
What happens during a chemical reaction?
Starting substances change into new substances.
True or false: Atoms can disappear during a chemical reaction.
False.
What was the mysterious reddish-brown substance in Westfield's water?
Rust / iron oxide.
Two substances look different and have different properties. Are they probably the same substance or different substances?
Different substances.
In a substance, atoms are often arranged in groups that do what?
Repeat over and over.
What are the starting substances in a chemical reaction called?
Reactants.
True or false: New atoms can suddenly appear during a chemical reaction.
False.
Was the rust already present in the well water?
No.
Why can chemists use properties to identify substances?
Each substance has its own set of characteristic properties.
If two models contain different types of atoms, can they represent the same substance?
No.
What are the substances formed during a chemical reaction called?
Products.
If an atom is present in a product, where must that atom have come from?
One of the reactants/starting substances.
What caused the rust to form?
A chemical reaction involving the iron pipes and fertilizer in the water.
The fertilizer and rust both contain oxygen atoms. Does this mean they are the same substance? Explain.
No. Substances can contain some of the same types of atoms but have different groups or arrangements of atoms.
Two models contain the same types of atoms but the atoms are grouped differently. Are they necessarily the same substance?
No. Different arrangements or groups of atoms can make different substances
What happens to atoms during a chemical reaction?
The atoms rearrange into new groups to form new substances
A fuel seems to disappear when it burns. What actually happens to its atoms?
Its atoms rearrange with other atoms to form new substances, often including gases.
Why could scientists conclude that the rust was not simply the same substance as the iron pipes?
Rust had different properties and different groups of atoms than the iron.
A student says, “If two substances have the same color, they must be the same substance.” What is wrong with this reasoning?
One property is not enough to identify a substance. Different substances can share a property but have different atoms, arrangements, or other properties.
How can an atomic-scale model help you decide whether two samples are the same substance?
Compare the types, numbers, and arrangements/repeating groups of atoms in each substance.
Iron from the pipes reacts with fertilizer and forms rust. Why is the rust a different substance from the iron and fertilizer?
The atoms from the reactants rearranged into different groups, producing a substance with different properties.
Some atoms from Westfield's iron pipes and fertilizer were not found in the rust. What must have happened to those atoms?
They must have rearranged to form another product because atoms cannot be created or destroyed.
Why did scientists predict that another product besides rust had to form in the Westfield reaction?
Not all of the atoms from the reactants were accounted for in the rust, and atoms cannot be destroyed, so the remaining atoms had to form another substance.