Vicky wanted to investigate water evaporation. She placed 50 mL of distilled water in three identical glass jars. She left one jar in the sunlight, one jar in the dark, and one jar in a shady area. After four hours, she measured how much water was still in each jar.

Which of the following variables was held constant in the experiment?

A.

amount of water placed in jars

B.

amount of water in jars at the end of the investigation

C.

air temperature

D.

light exposure

in 1783 cavendish was working with his hydrogen gas and found that when he burned it and condensed the vapor it was water. this was very significant since it disproved the greek theory of elements completely since water was not a simple substance but the product of two gases. it was lavoisier who hearing of the experiment gave cavendish's gas the name hydrogen ("water-producer") and added that hydrogen burned by combining with oxygen and that water was a hydrogen-oxygen combination.

explanation:

answer: semi-infinite solid initially at a uniform temperature of 400 ◦c is cooled at its surface by convection. the cooling fluid at a constant temperature of 200 ◦c has a convective coefficient (ha) of 250 w/m2.k. the physical properties of the solid: k = 20 w/m.k and α = 4 * 10-5  m2/s. using δx = 0.04 m and δt = 10 s. write the finite difference equations describing the transient heat transfer of the first five δx and the temperature profile after 30 s.