Which of the changes are physical changes

1. Scientists are concerned about the global temperature rise, the increase in CO2 in our atmosphere, the melting glaciers and other impacts of climate change and our over use of fossil fuels.

What will happen when a light bulb is added on the left side of this circult

What is the half-life of sodium-25 if 1.00 gram of a 16.00-gram sample of sodium-25 remains unchanged after 237 seconds? (1) 47.4 s (3) 79.0 s (2) 59.3 s (4) 118 s

Suppose a 20 gram cube of aluminum were cut into four equal parts. How would the density of one part be related to the density of the whole cube?

The density of water is 1.00g/ml at 4 degrees Celsius. How many water molecules are present in 2.56ml of water at this temperature?

For the reaction represented by the equation 2na + cl2® 2nacl, how many grams of chlorine gas are required to react completely with 2.00 mol of sodium?

Transuranium elements are elements larger than uranium that are produced via transmutation. a. True b. False

Explain why glacial deposits have been found in Africa?

Which of the following would result in butyl phenyl ether as the major product? a. Reaction of phenoxide with 1-bromobutane b. Reaction of 1-butanol with bromobenzene c. Reaction of phenyl magnesium bromide with 1-butanol d.

A 200-gram sample of a radioactive nuclide is left to decay for 60 hours. At the end of 60 hours, only 25 grams of the sample is left. What is the half-life of the nuclide sample? 60 hours 30 hours 40 hours 20 hours - - - > I think 20?