Chapter 3.1: Relative Atomic Mass Flashcards
What is a measure for how much matter an object contains?
Mass
An object with more mass has more ____ than an object with less mass.
Particles.
What is an electronic balance that measure’s mass to the hundredth of a gram, giving 2 decimals? (0.01 g)
A centigram balance.
How do the sensitive analytical balances in professional labs stop air-current/dust from affecting their reading?
The measuring pan sits inside a sealable enclosure.
How do you find the mass of a small object with a higher precision (more decimal places)
Measure a large amount of that object and divide by the number of objects to find the “unit rate”.
Does measuring a large quantity and dividing by the exact quantity give an actual or average mass of each object?
Average (you are assuming they are all the same size).
Why do we choose to use the atom’s relative mass instead of actual mass in chemistry?
Because the atoms and molecules are so small that directly measuring their actual masses is impossible.
What do you call the ratio of one object’s mass to that of another object?
Relative mass.
What is the one necessary criteria for determining relative mass?
The two groups you are comparing have to have the exact same number of objects.
Does the amount of objects you use to determine relative mass matter?
No, you can use any amount as long as you use the same amount for both groups.
Can you determine the relative mass if you don’t have equal groups of objects?
Yes, as long as you know the ratio you do have, and add an additional step of multi/divi the ratio to make it 1:1
What is a limitation to the method of determining relative mass?
You are assuming that each object in your group has the same exact mass.
All samples of a given compound contain the same elemental composition by mass, meaning their elements are always present in a fixed ratio.
The Law of Constant Composition.
What did John Dalton wrongfully assume about the ratio of elements in a compound?
That the elements always combined in the simplest ratio, 1:1.
What is a benefit of absolute measurements?
You can measure them directly without comparing to anything else.
