Which of the following describes a physical change? a. formation of a new substance caused by combining substances
b. water changing from liquid to gas through evaporation or boiling
c. formation of a new substance caused by application of heat

In which situation has the independent variable for the experiment been changed? check all that apply. changed from counting the number of duckweed at day 0 and day 14 to counting them every day changed from testing duckweed growth in beakers to testing duckweed growth in large outdoor tanks changed from testing the effect of ph on duckweed growth to testing the effect of light levels on duckweed growth changed from testing the effect of acid ph on duckweed growth to testing the effect of basic ph on duckweed growth

Amira pulls a 3 pound wagon 4 feet. how much work has she done?

Explain why electric current cannot exist if a current doesn't have a voltage source.