The half life of radium is 1600 years. After bow many years 25% of radium block remain undecayed?

Orque can be calculated by multiplying the force (n) applied at 90? to the lever arm at a distance (m) from the pivot point (point of rotation), the compound si unit for the torque is n? m. if the force (at 90? to the lever arm) applied is 15 n and it is applied at 2.0 m from the pivot point (point of rotation), what is the torque on the lever?

Transfer chemicals from one location to another to weather objects. a-water b-physical weathering c-chemical weathering

If the chemical properties of a substance remain unchanged and appearance or shape of a substance changes it is called a ?