Which of the following changes is an exothermic chemical change

Boiling water

Melting ice

Chopping wood

Fireworks exploding

Give the correct symbols to identify an atom that contains (a) 4 protons, 4 electrons, and 5 neutrons; (b) 23 protons, 23 electrons, and 28 neutrons; (c) 54 protons, 54 electrons, and 70 neutrons; and (d) 31 protons, 31 electrons, and 38 neutrons.

A ballon is inflated with 2.42L of helium at a temperature of 27.0°C. When put in the freezer, the volume changes to 2.37L and - 8.8°C, and the pressure is measured to be 754torr. What was the initial pressure?

In a solution of sugar, we used 500ml to make 50g/l solution. How much sugar was used?

At 25°c, the vapor in equilibrium with a solution containing carbon disulfide and acetonitrile has a total pressure of 250. torr and is 85.7 mole percent carbon disulfide.

A 22.4-L sample of which of the following substance, at STP, would contain 6.02 x 10^23 representative particles? A. Gold B. Sodium chloride C. sulfur D. carbon dioxide

Which statement describes the redox reaction that occurs when an object is electroplated? A. It is spontaneous and requires an electric current. B. It is spontaneous and produces an electric current. C.

How are electromagnetic different than all other waves

Find the ratio of speeds of an electron and a negative hydrogen ion (one having an extra electron) accelerated through the same voltage, assuming non-relativistic final speeds. Take the mass of the hydrogen ion to be 1.67*10^{-27} kg.

A type of rock that undergoes changes because of heat and pressure

How many milliliters of a 1.25 molar HCL solution would be needed to react completely with 60 g of calcium metal Ca+2HCl - - > CaCl2 + H2