Which of the following is evidence of a chemical change?

phase change

the formation of a gas

mass change

change in surface area

Ava's best friend has an indoor cat. Ava notices that she sneezes every time that she visits her friend. Ava suspects that she is allergic to cats but is unsure. What is the best thing for Ava to do next?

1. For HF and HBr, the partial positive charge on H atom is 0.29 and 0.09, respectively. Use electronegativities (EN) to explain why the partial charge on H in HF is more positive than the partial charge on H in HBr.

Which of the following elements would you expect to behave most like magnesium? a) sodium b) calcium c) aluminum d) scandium

Is phenoxyethanol an organic compound?

A brick measures 25cm by 12 cm by 13 cm. What is the volume of the brick in cm3? How many milliliters of water would this brick displace?

Using special equipment which layer of the sun atmosphere is visible during a total solar eclipse

The characteristic flame test colors of metal ions are due to atomic emission spectra. Duscuss the relationship between the absoption and emission of light and the factors responsible for flame test colors.

Should a bartender use ice and scoop directly from ice machine or use an ice holding device and scoop to make drinks and refill drinks from

What classification should this reaction have? 4Al + 3O2 → 2Al2O3

If you start with 100 grams of a radionuclide, how much will you have after two half-lives have passed?