Answer:
concave lens
Explanation:
it's concave lens because it diverges the ray/beam of light.
Measure how much water has gone in, so you know the concentration.
Answer:
c tarnishes in air
Explanation:
After silver has been exposed to air that contains sulphur gases, discoloration would occur. there would be darkening that is caused by the reaction with gases.When any silver object tarnishes, it brings about a disfiguring of that object. Hydrogen sulphide would be needed for this to happen. silver sulphide is black and a if a thin layer should form on any surface, it ill darken it. This is what we refer to as tarnishing.
Answer:
a) 
is the mass of 1 mole of bricks.
b) 
moles of bricks have a mass equal to the mass of the Earth.
Explanation:
a) Mass of brick = 4.0 kg
1 mole = 
particles/ atoms/molecules
Mass of 
bricks :
is the mass of 1 mole of bricks.
b)
Mass of the Earth = M = 
Mass of 1 mole of brick = m=
Let the moles of brick with equal mass of the Earth be x.
moles of bricks have a mass equal to the mass of the Earth.
