Work is the energy transferred to or from an object as it moves under a force. The key is how much of the force actually acts along the direction of the displacement. When the force points opposite to the motion, the force resists the movement, so energy is taken away from the object and the work is negative. This can be seen from W = F · d = |F||d| cos(theta): with theta = 180 degrees (force opposite to displacement), cos(theta) = -1, giving negative work. Negative work means the object's kinetic energy decreases (often turning into heat). If the force and displacement align, the work is positive and adds energy to the object. If there’s no force or no movement, the work is zero.

The rate of a reaction depends on how often reacting particles meet, and for reactions involving a solid and another reactant, only the particles at the solid’s surface can participate. Increasing the surface area of the solid means more of its particles are exposed to the other reactant, producing more collisions per unit time and speeding up the reaction. That’s why breaking a solid into smaller pieces or grinding it into a powder often makes a reaction go faster—the surface area goes up a lot, so contact and collision opportunities increase. The other statements don’t fit because temperature changes usually speed up reactions when you raise it, not slow them; increasing the container volume lowers the concentration of reactants and tends to slow the rate; and a catalyst provides an alternative pathway that speeds up the reaction, not slows it.

Mass is the amount of matter in an object and doesn’t change with location. Weight is the gravitational force acting on that mass, so it depends on how strong gravity is. The relationship is W = m × g. Because gravity (g) varies—from Earth to the Moon to space—weight changes with gravity while mass stays the same. For example, you’d weigh less on the Moon due to weaker gravity, even though your mass is unchanged. If gravity were eliminated, weight would be zero while mass remains.

The major components of the air at Earth's surface are nitrogen and oxygen, making up the vast majority of molecules, with small amounts of argon, carbon dioxide, and other trace gases. In dry air, nitrogen is about 78% and oxygen about 21% by volume (mole fraction). The remaining roughly 1% consists of argon, carbon dioxide, neon, helium, methane, and other trace gases. This is why the option listing about 78% nitrogen, 21% oxygen, and the rest as argon, CO2, and trace gases is the best description for the lowest atmospheric layer. The other options mismatch these proportions or misstate the presence of certain gases (for example, placing a large fraction of carbon monoxide or an unusually high amount of argon), which doesn’t reflect the typical composition of dry air at sea level.