Carbon dioxide sublimation
water evaporate
physical change is just change between solid/liquid/gas, other two are chemical changes
Water
Water is a compound because it is made from more than one kind of element (oxygen and hydrogen).
Answer : 12 karat
Explanation : When pure gold is considered to be 24 karat then if its 50 mol% silver and 50 mol% silver then using karat scale calculation;
Karat/24 X 100 = 50 mol% (for gold) in alloy
So, Karat = (50 X 24) / 100 = 12 karat.
Hence the alloy will be of 12 karat.
The half life of carbon-14 is 5700 years. (Half life is the time taken by a radioactive isotope to decay by half of its original mass).
Let A₀ be the initial amount of carbon-14 that is found in living matter (t=0 years), to determine when there was 44.5% of A₀ left.
44.5 = 100 × (1/2)^n, where n is the number of half lives
0.5^n = 0.445
n = log 0.445/log 0.5
n = 1.168
But 1 half life is 5700 years
Therefore, the number of years will be 5700 × 1.168 = 6658.299725 years
≈ 6658.30 years
Astronauts experience weightlessness which is the apparent loss of weight of an object that is falling in gravitational field
