Here's how to calculate the mass and weight of 1 liter of water:

1. Mass:

* Density of water: 1 kg/L (kilogram per liter)

* Volume of water: 1 L

* Mass = Density x Volume

* Mass = (1 kg/L) x (1 L) = 1 kg

Therefore, the mass of 1 liter of water is 1 kilogram.

2. Weight:

* Weight = Mass x Acceleration due to gravity (g)

* g = 9.8 m/s² (approximately)

* Weight = (1 kg) x (9.8 m/s²) = 9.8 Newtons

Therefore, the weight of 1 liter of water is approximately 9.8 Newtons.