C. The mass number is the amount of Protons and electrons there are combined, so 200 - 80 is 120.
Physical change: a change in which no new substances are formed. the form of the substance is changed but not it's chemical composition (ice melting, bread toasting)
chemical change: any change that results in the formation of new chemical substances. this type of change modifies molecules and atoms by making and breaking the bonds between atoms! (iron rusting, gas burning)
so basically a physical change just changes the appearance of a substance, but a chemical change changes the makeup on a molecular level. i hope this helps you out!
<span>A fizz saver forms an airtight seal around the now-upsidedown soda bottle, and the pressure exerted by the drink and the atmospere outside pushes out the drink through the slightly-elevated spout. The CO2 gas does not fizz out because it stays at the bottom of the upside-down bottle. Thus the CO2 gas is trapped and the drink is carbonated at a longer time.</span>
Answer:
Explanation:
We shall find out volume of air at NTP or at 273 K and 10⁵ Pa ( 1 atm )
Let it be V₂
V₂ = 7.87 litres
22.4 litres of any gas is equivalent to 1 mole
7.87 litres of air will be equivalent to
7.87 / 22.4 moles
= .35 moles .
With reference to radioactive material, half-life is the time required to 50% depletion of initial amount of material.
Given: Initial amount of radioactive material = 40 g
Half life = 4 days.
Therefore, After 4 days, amount of compound left = 40/2 = 20 g
After 8 days, i.e 2 half-life, amount of compound left = 20/2 = 10 g
Finally after 12 days, i.e. 3 half-life, amount of compound left = 10/2 = 5 g
Thus, 5 <span>grams will remain after 12 days</span>
