Early Atomic Ideas
Who believed matter was made of tiny particles called atomos?
Democritus.
What does the law of conservation of mass state?
Matter cannot be created or destroyed during an ordinary chemical reaction.
What does the law of definite proportions state?
A pure compound always contains the same elements in the same mass ratio.
What did Dalton conclude all matter is made of?
Atoms.
Who believed matter could be divided indefinitely?
Aristotle.
10 g of one substance reacts with 15 g of another in a closed system. What is the total mass of the products?
25 g.
A 9 g sample of water contains 8 g oxygen. How much oxygen is in 18 g of water?
16 g oxygen.
According to Dalton, how do atoms combine to form compounds?
In simple whole-number ratios.
What is the main difference between atomism and the continuous theory of matter?
Atomism says matter consists of discrete particles; continuous theory says matter can be divided indefinitely.
A reaction starts with 40 g of reactants and produces 25 g of one product. What is the mass of the other product?
15 g.
CO has 16 g oxygen per 12 g carbon; CO₂ has 32 g oxygen per 12 g carbon. What is the oxygen mass ratio?
16:32, or 1:2.
What two premises formed the basis for Dalton's model?
Atoms of different elements combine to form compounds, and atoms of different elements have different masses.
Why was Dalton's model more scientifically convincing than the Greek atomic ideas?
Dalton supported his theory with experimental evidence and measurements.
Why does a burning log leave behind less mass in ash than the original log?
Gaseous products escape into the air; the total mass is still conserved.
Explain the difference between definite proportions and multiple proportions.
Definite proportions concerns the fixed composition of one compound; multiple proportions compares the masses in different compounds made from the same two elements.
Name one of Dalton's conclusions that scientists later revised and explain why.
Atoms are divisible into subatomic particles; or atoms of the same element can have different masses because of isotopes.