Heather rolls a marble over sand paper and then over a flat table. Which statement best describes the observations she made? When the marble is pulled, the friction on the table is greater.
When the marble is pushed, the friction is greater on the sandpaper.
The amount of friction is about the same on both surfaces.
The force of gravity pulling the marble lessens the friction between the surfaces.

The lattice enthalpy (formation of ionic solid from ions in the gas phase) for agcl(s) is -916 kj/mol and the hydration enthalpy (dissolution of gaseous ions into water) is -850 kj/mol. how much heat (in joules) is involved in forming 1l of saturated agcl solution (1.8 × 10-4 g / 100 ml water) by dissolving agcl(s)? assume solution volume does not change much upon dissolution. the equations are given below. ag+(g) + cl−(g) æ agcl(s)