If an unshielded sample of radioactive material emits alpha particles, what effect will it have on a person sitting in the next room? (assume the wall between rooms is composed of concrete.)
none, because the wall will block the radiation.
the radiation will travel through the person’s body.
none, because the radiation will bounce off the person’s body.
the radiation will be totally absorbed by the person’s body.

Agroup of students is studying convection currents. they fill two identical balloons with the same amount of helium. one balloon is placed in a freezer and the other in an area with warm air. after 10 minutes, the balloons are released from a height of 1 meter. which of the following do the students most likely observe? a. the balloons both rise. the cold balloon is larger than the warm balloon. b. the balloons rise at the same rate. both balloons are the same size. c. the warm balloon expands and rises. the cold balloon shrinks and sinks. d. the cold balloon expands and rises. the warm balloon shrinks and sinks.

8.98 dm3 of hydrogen gas is collected at 38.8 °c. find the volume the gas will occupy at -39.9 °c if the pressure remains constant.

Identify arrows pointing to bonding electrons. done h-0-0-h ) intro