Explanation:
A change that does not cause any change in chemical composition of a substance is known as a physical change.
For example, mass, density, volume etc are all physical changes.
On the other hand, a change that brings change in chemical composition of a substance is known as chemical change.
For example, combustion, toxicity, reactivity etc are all chemical changes.
Hence, following statements are identified as chemical or physical changes as follows.
(a) Oxygen gas supports combustion : Chemical change
(b) Fertilizers help to increase agricultural production : Chemical change
(c) Water boils below 
on top of a mountain : Physical change
(d) Lead is denser than aluminum : Physical change
(e) Uranium is a radioactive element : Chemical change
Answer:
Heat is the <u>total</u> energy in a substance. Temperature is a <u>measure</u> of the <em>average</em> energy in a substance.
At a definite amount of solute and at a definite tempreture it is dissolved in utane above that it remain unsoluble
The dependent variable is 'Number of plants' which is the correct answer.
The independent variable is CO₂ levels in ocean water, however, the growth of plants in ocean water depends on the CO₂ levels. Higher CO₂ is level is conducive to the growth of plants.
Plants use CO₂ and water in photosynthesis to prepare food in the presence of light.
6CO₂ + 6H₂O + light energy = C₆H1₁₂O₆ + 6O₂.
Answer:
1: The speculation that continents might have 'drifted' was first put forward by Abraham Ortelius in 1596. The concept was independently and more fully developed by Alfred Wegener in 1912, but his hypothesis was rejected by many for lack of any motive mechanism. 2: The most obvious evidence for continental drift is that the continents appear to fit together like pieces of a puzzle. But scientists were skeptical , and Wegener needed additional evidence to support his hypothesis. Glaciers covered large areas that are now parts of these continents.
