What evidence of a chemical reaction might you see when dropping an alka-seltzer tablet in a glass of water

A chemical reaction is characterised by evidence of a chemical change; such as a change in colour, production of a gas or a solid, or a change in temperature. evidence of a gas being produced is the bubbles that form then the tablet is dissolving, and theres is likely to be a slight change in temperature due to the energy produced, but this would not likely be obvious

The answer is b carbon-14. the radioactive isotope of carbon used in carbon dating has a half-life of 5730 years. potassium-40 is used to date 1.25 billion years