The substance that acts as solvent  and lubricant , as vehicle for transporting  nutrient and waste; and as a medium for  temperature regulation and  chemical processes is:

Developmental contextualism places an impact on development. 

—–  are environmental “opportunities” for developing motor skills.

Max heart rate increases with older age. 

A 40.00 mL solution containing an unknown concentration of H2SO4 is titrated with 22.62 mL of 0.2000 M NaOH solution.  Calculate the molarity of the H2SO4 solution.

Witherite is a mineral that contains barium carbonate. If a 1.68-g sample of witherite were to react completely with 24.6 mL of 0.2558 M HCl, what would be the percent of barium carbonate in the witherite sample? (Barium carbonate is the only compound present that reacts with the hydrochloric acid.)                                BaCO3   +   2 HCl     →     BaCl2   +   CO2   +   H2O

A hypothetical element has an atomic weight of 123.45 g/mol.  It consists of 2 isotopes having masses of 124.05 g/mol and 122.67 g/mol.  What is the percent abundance of the lightest isotope?

During the nuclear decay of the 208Po isotope, two neutrons and two protons are lost, resulting in which isotope?  

How many Cl atoms are in 0.0728 g of PCl3?    

Sodium azide is the chemical used in airbags to inflate them when you crash. It decomposes into elemental sodium and nitrogen gas as shown in the reaction below. Elemental sodium is dangerous because of its high reactivity, so other components, such as KNO3 and SiO2, are added to airbags to react with the sodium and turn it into harmless silicates. Using the balanced reactions below, determine how many moles of K4SiO4 are formed when 4.0 moles of NaN3 reacts. 2 NaN3(s)     →   2 Na(l)    +   3 N2(g) 10 Na(l)   +    2 KNO3(s)   →    K2O(s)  +  5 Na2O(s)  +   N2(g) 2 K2O(s)   +   SiO2(s)  →    K4SiO4(s)