Which examples represent chemical changes? Check all that apply.

burning wood

souring milk

melting copper to join two copper pipes together

browning of a cut apple

cutting a potato into small pieces

If the early atmosphere of the earth was composed of carbon dioxide, why does the present atmosphere contain oxygen molecules?

Two iron rods are placed horizontally, touching end-to-end. One end of one rod is heated. After some time, the other rod also feels warm to touch. How did the heat travel from the heated rod to the one that was not heated?

Why are lenses made from amorphous solids?

What type of bonding found in copper carbonate

Calculate the number of moles of each component element in the compound. #moles H = #moles S = #moles O=

The hydrogen gas from the reaction of 1.0 g of iron with excess hydrochloric acid is collected in a 15.0 L flask at 25 degrees Celsius. What is the pressure of the hydrogen gas in this flask?

Which electrons participate in chemical bonding? a. core electrons b. valence electrons c. the innermost electrons d. any electrons

You can find the pH of a substance by using a. plain paper. b. a thermometer. c. litmus indicator. d. a conductivity tester.

The absorbance of a chlorophyll a standard solution in ethanol (density = 0.785 g/mL) is measured in a 1.3 cm cuvette or path length. The absorbance is 0.765 and the molar absorptivity coefficient is 86,300 M-1cm-1.

How does the surface of the earth change slowly over time