Hydrogen gas (H2) can be found in trace amounts in Earth's atmosphere.
Whh of these statements describes a physical property of hydrogen?
(A) Hydrogen is found in acids.
(B) Hydrogen gas is highly flammable.
(C) Hydrogen reacts with oxygen to form water.
D
Hydrogen gas is less dense than oxygen gas.

How many variables are altered in a good experiment? a.1 b.0 c.2 d.3

Animal bodies (and even plant bodies for that matter) are complex enough that life couldn't exist without enzymes. enzymes are usually large, complex biological catalysts that are expensive to make. enzymes speed up the rate of chemical reactions without being used up during the reaction (they can be reused many times). they are highly specific in the reactions they regulate. knowing what enzymes are and how they function, why does this explain why complex life forms could not exist if there were no enzymes.

Ricardo notices that when he plays soccer in the rain, his ball does not seem to go as far after a kick. what is the best scientific question that ricardo could ask about this observation? is soccer better played in the rain or sun? how does rain affect the distance a soccer ball can travel? how does rain affect the speed of a soccer ball? is soccer affected by the rain?