Atoms, Molecules and Compounds
What is the smallest unit of matter that we have discussed?
Atom
When water freezes, is it a physical or chemical change?
Physical
What law states that matter cannot be created or destroyed?
Law of Conservation of Mass
What do we call the substances you start with in a chemical reaction?
Reactants
What gas is most present in the air we breathe?
Nitrogen (N)
What do you call 2 or more atoms bonded together?
When wood burns, what type of change occurs?
Chemical
If you start with 10 g of reactants, how many grams of product should you end with?
10 g (mass is conserved)
What do we call the substances formed in a chemical reaction?
Products
What gas do humans exhale (breathe out)?
Carbon dioxide (CO₂)
What is the difference between an element and a compound?
Elementa have one type of atom; compounds have two or more elements chemically bonded.
Name one clue that a chemical change has occurred.
Color change, temperature change, gas production, precipitate formation, or odor change.
What happens to the atoms during a reaction?
They rearrange into new combinations but are not lost.
What does a chemical equation show?
It shows how atoms rearrange to form new substances.
What kind of reaction happens when iron rusts?
Chemical reaction (oxidation)
How many atoms are in one molecule of CO2 (and what are they)?
3 atoms (1 carbon, 2 oxygen)
Why is dissolving sugar in water not a chemical change?
No new substance is formed; the sugar can be recovered.
In a closed system, what would happen to the total mass after a reaction?
It stays the same.
How can you show conservation of atoms in a reaction model?
Make sure the number of each type of atom is equal on both sides.
Why does baking a cake count as a chemical reaction?
New substances form through heat; cannot reverse easily.
What do subscripts (the small numbers) in a chemical formula tell you?
The number of atoms of each element in one molecule of the substance.
In a chemical change, what happens to the atoms?
They rearrange to form new substances.
In a reaction where vinegar reacts with baking soda in a sealed bottle, why does the mass not change?
All gases are trapped; no matter escapes.
In the reaction H₂ + O₂ → H₂O, which side represents the reactants?
The left side
What type of reaction causes bubbles in our bottle experiment?
Chemical reaction