Which formula represents an ionic bond? 1 NaCl 2 N2O 3 HCl 4 H2O

Why do scientists look for patterns in the world? a. patterns can explain observations. b. patterns never change, no matter what. c. patterns are easy for scientists to detect. d. patterns are all the same, through all time.

Calculate the number of kilojoules to warm 125 g of iron from 23.5°c to 78.0°c.

Which of the following is an indication that a substance has undergone a chemical change? a. no new product has been formed. b. the color of the substance has not changed. c. the original constitute has not changed. d. the molecular structure has changed.