Answer:
coral bleaching is when the temperature of the water changes (even slight changes in temperature effect coral) and the coral reacts negatively to it causing it to die. unfortunately corals cannot recover once they have been bleached.
Answer:
Electronegativity is a measure of an atom's ability to attract shared electrons to itself. On the periodic table, electronegativity generally increases as you move from left to right across a period and decreases as you move down a group.
Explanation:
Hope it is helpful....
A pure substance refers to an element or a compound that has no component of another compound or element. Pure substances are made of only one type of atom or molecule. Hydrogen gas and pure iron are examples of pure substances. Hydrogen consists of hydrogen atoms only while iron consists of only iron atoms. Mixing two pure substances results in a mixture. To separate the two, scientists use a method known as filtration. Mixtures can either be homogeneous or heterogeneous. The measure used to determine how pure a substance may be called purity. Besides hydrogen and iron, other pure substances include gold, diamonds, sugar, and baking soda.
Explanation:
Since, density is the amount of mass present in per unit volume.
Mathematically, Density = 
As density is directly proportional to mass of a substance. So, more is the density of a substance more will be its mass. And, when more is the mass of a substance then it is likely to sink at the bottom.
Here, it is given that density of oxygen is more than the density of nitrogen. Therefore, balloons filled with oxygen will sink in the air.
On the other hand, balloons filled with nitrogen will rise in the air.
