system: 
User: Which is heavier : 1 kg of steel or 1 kg of feathers ?
ChatGPT: Both 1 kg of steel and 1 kg of feathers weigh the same, which is 1 kg. The weight of an object is a measure of the force exerted on it by gravity, and 1 kg is equal to the weight of approximately 9.8 Newtons (N) on the surface of the Earth. So, regardless of the material, if two objects have the same mass, they will have the same weight on Earth. 

It is worth noting, however, that the volume of 1 kg of feathers is much larger than the volume of 1 kg of steel due to their different densities. Steel is denser than feathers, so 1 kg of steel occupies much less space than 1 kg of feathers.