Question 1: Define the term 'half-life' in the context of radioactive decay.

Answer: Half-life is the time required for half of the radioactive nuclei in a sample to decay.

Question 2: Explain why the concept of half-life is important in determining the age of archaeological artifacts.

Answer: Because it allows scientists to estimate the time elapsed since the artifact was formed by measuring the remaining radioactive material.

Question 3: Describe the mechanism of radioactive decay that leads to a decrease in the number of radioactive nuclei over time.

Answer: Radioactive decay is a random process where unstable nuclei spontaneously emit radiation, transforming into a more stable nucleus, which results in a decrease in the number of radioactive nuclei over time.

Question 1: A sample of radioactive isotope has a half-life of 10 hours. How much of a 100-gram sample remains after 30 hours?

Answer: 12.5 grams

Question 2: If 25 grams of a radioactive substance with a half-life of 8 hours remains after a certain period, how long has it been since the decay started?

Answer: 16 hours

Question 1: Design a simple hypothetical experiment to measure the half-life of a radioactive isotope. List the variables involved and safety precautions to consider.

Answer: Students should describe measuring initial activity, recording activity at regular intervals, and calculating the time taken for activity to reduce by half. Variables include initial activity, time interval, and environmental conditions. Safety precautions include using lead shields, wearing protective gear, and handling radioactive materials with proper protocols.

Question 2: Identify three safety precautions necessary when working with radioactive materials in a laboratory setting.

Answer: Wearing protective gloves and goggles, using lead shields, working in a designated radioactive area, minimizing exposure time.

Question 1: A scientist measures the remaining radioactive material in a sample at different times and finds that after 5 hours, 75 grams remain from an initial 100 grams. What is the half-life of this isotope?

Answer: Approximately 3.3 hours

Question 1: Explain how the concept of half-life is used in Carbon-14 dating to determine the age of ancient fossils.

Answer: Because Carbon-14 has a known half-life, measuring the remaining C-14 in fossils allows scientists to estimate how long ago the organism died.

Question 2: Describe a practical application of radioactive isotopes with long half-lives in industry or medicine.

Answer: Radioisotopes with long half-lives are used in medical imaging and cancer treatment, such as in radiotherapy or diagnostic scans.