What's the difference between groups and periods in a periodic table?

Which statement correctly describes the reactivity of noble gases, according to the octet rule? Their atoms have eight electrons in their valence shells, so noble gases are very reactive.

A fish maintains its depth in fresh water by adjusting the air content of porous bone or air sacs to make its average density the same as that of the water. Suppose that with its air sacs collapsed, a fish has a density of 1.05 g/cm3.

Which of the following is evidence that the universe began with the big bang theory

Wavelength is measured in hertz true or false?

Why should you never determine the mass of a hot object?

The first law of thermodynamics states that ΔE = Q - W. Is this also a statement of the principle of conservation of energy? Yes, the heat added and the change in internal energy of the gas equal the work done by the piston.

How can we calculate the density of a sustance that has irregular volume

A two stage rocket leaves its launch pad moving vertically with an average acceleration of 4 m/s2. at 10 s after launch the first stage of the rocket (now without fuel) is released.

A liquid filled sealed system has cylinders with movable pistons on each end. The face of one piston has an area of 5 cm². The other piston has an area of 500 cm² and is supporting a weight of 2 kN on it.

A turntable is spinning on a frictionless axle when a ball of putty is dropped onto it from above. The putty sticks to the turntable when it lands. Is angular momentum conserved for the turntable and putty (the system) during this process?