How are the sizes of stars measured?

I just need a simple answer

When an atom forms a positive ion (by losing electrons). Will the radius of an ion change from the radius of an atom? Explain with the example of Sodium atom (Atomic no. 11) and Sodium ion.

What is the density of an unknown if 7.82g of it occupies a volume of 3.63ml

Which substance cannot be broken down by a chemical change? (1) ammonia (2) mercury (3) propane (4) water

In that universe, which of the following objects would require quantum mechanics to describe, that is, would show both particle and wave properties? Which objects would act like everyday objects, and be adequately described by classical mechanics?

A student can eat 4.0 M& Ms every 1.00 seconds. If an M& M has a mass of 63g, determine how many kilograms of M& Ms can be eaten by a class of 20 students in 3.75 hours.

Which statements describe abiotic factors in an environment?

A ball rolling across the ground in Death Valley will slow and eventually stop. Why? - the ball's kinetic energy evaporates. - the ball's force is destroyed. - the friction of the ball changed the force to negative ions.

Calculate ∆h0 for the following reaction. br2 ( g. → br2 (l) ∆hf0 br2 ( g. = 30.91 kj/mol; ∆hf0 br2 (l) = 0 kj/mol)

Ethyl alcohol has a latent heat of vaporization of 850 J/g. Water has a latent heat of vaporization of 2260 J/g. Container A contains 1.0 kg of ethyl alcohol. Container B contains 1.0 kg of water. Both liquids are brought to a boil.

The greatest composition by mass in an atom 17/8 O is due to the total mass of its