If the half-life of a sample of a radioactive substance is 30 seconds, how much would be left after 60 seconds? <span>
A. one-fourth</span>
M₁=50 g
m₀=60 g
w=100m₁/m₀
w=100*50/60=83.3%
Answer:
Explanation:
a. change of colour:
A chemical reaction rearranges the constituent atoms of the reactants to create different substances as products. The products have different molecular structures than the reactants. Different atoms and molecules radiate different colours of light. Hence, there usually is a change in colour during a chemical reaction.
Eg: copper reactions with the elements
b. Evolution of gas:
A gas evolution reaction is a chemical reaction in which one of the end products is a gas such as oxygen or carbon dioxide.
Eg: ammonium hydroxide breaks down to water and ammonia gas.
c. Change of smell :
Production of an Odor Some chemical changes produce new smells. ... The formation of gas bubbles is another indicator that a chemical change may have occured.
Eg: The chemical change that occurs when an egg is rotting produces the smell of sulfur.
d. Change of state:
A chemical reaction is a process in which one or more substances, also called reactants, are converted to one or more different substances, known as products.
Eg: candle wax (solid) melts initially to produce molten wax (liquid)
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Atomic number, because the atomic number is unque to each individua element.
The answer is letter C. hydrogen bonds. Surface tension in water, which makes water form drops and causes the surface to form a curve above the mouth of a container, results from the water molecules being strongly held by H bonds to those water molecules beside and beneath them. The cohesion among water molecules and the adhesion of water to other materials like rock and soil make capillarity possible.
