An 800. mL sample of oxygen at 90.00C and was cooled at constant pressure until it has a volume of 400.0 mL. What was the final Celsius temperature of this gas?

C, small, hard spheres with insignificant volumes

Zinc contains about 30 protons 

The population of unionid mussels decreased after zebra mussels were introduced. zebra mussels competed with the unionid mussels for food. the zebra mussels were able to displace the unionid mussels, allowing the zebra mussel population to increase  over the years. the unionid mussel population decreased because  of lack of food.