Answer:
If anything but H2O were found, it would be evidence of a chemical change. Therefore, 4 is the only viable evidence that it was a physical change of H2O liquid to H2O gas.
Picometre is equal to 1·10⁻¹²m
175·10⁻¹² m = 1,75·10⁻¹⁰ m
Answer:
Considering the half-life of 10,000 years, after 20,000 years we will have a fourth of the remaining amount.
Explanation:
The half-time is the time a radioisotope takes to decay and lose half of its mass. Therefore, we can make the following scheme to know the amount remaining after a period of time:
Time_________________ Amount
t=0_____________________x
t=10,000 years____________x/2
t=20,000 years___________x/4
During the first 10,000 years the radioisotope lost half of its mass. After 10,000 years more (which means 2 half-lives), the remaining amount also lost half of its mass. Therefore, after 20,000 years, the we will have a fourth of the initial amount.
The boiling point of a substance is a physical property.
A physical property of a material or substance is one that can be observed without changing or altering the composition of the material.
Examples are mass, Density, Color, solubility, boiling point, melting point .
A chemical property of a substance is one that describes how the material changes into a completely different substance and is observed only during a chemical reaction.
Examples of chemical properties include types of chemical bonds, heat of combustion, reactivity with other metals, oxidation state and enthalpy of formation.
