Understanding Half-Life and Radioactive Decay

What does the term 'half-life' refer to?

• The time it takes for a substance to stop emitting radiation

• The time it takes for a substance to double in amount

• The time it takes for a substance to completely decay

• The time it takes for half of a radioactive substance to decay

What is radioactive decay?

• The process by which atoms combine to form molecules

• The process by which unstable atomic nuclei lose energy

• The process by which a substance increases in mass

• The process by which a substance emits light

Why does half-life happen?

• Because atoms are stable and do not change

• Because unstable nuclei release energy to become more stable

• Because substances gain energy over time

• Because atoms split into smaller parts randomly

What does a half-life graph typically look like?

• A straight line going upward

• A flat horizontal line

• A curve that decreases exponentially

• A zigzag pattern

After 3 half-lives, how much of a 100-gram radioactive substance remains?

• 50 grams

• 12.5 grams

• 100 grams

• 25 grams

Why does the amount of a radioactive substance never reach zero?

• Because the substance regenerates itself

• Because half-life only reduces the amount by half each time

• Because the substance becomes stable after one half-life

• Because decay stops after a certain point

How can you identify the half-life of a substance from a graph?

• By finding the time it takes for the amount to double

• By finding the point where the graph stops

• By measuring the time it takes for the amount to decrease by half

• By looking at the highest point on the graph

What happens to the amount of a substance after one half-life?

• It doubles

• It decreases by half

• It remains the same

• It decreases to zero

If a substance starts with 200 grams, how much remains after 2 half-lives?

• 100 grams

• 25 grams

• 50 grams

• 200 grams

What is the main purpose of radioactive decay?

• To make substances heavier

• To increase the energy of a substance

• To stabilize unstable atomic nuclei

• To create new elements