Answer:
They can be dated using radioactive carbon. But for rocks older than 50 thousand years they look for layers of igneous rock or volcanic ash above and Bellow the layer of rock/fossil.
Chemical property is the property of the substances that describes the ability of the substance to involve in chemical reactions. Physical property is that which does not change the chemical composition of the substances. The following properties of water that it is transparent and tasteless in its pure form and it freezes at a temperature of 
are physical properties as they simply indicate the change in physical state without any change in chemical composition of water.
The other two properties that water reacts with halogens to form oxygen gas as one of the products and water decomposes to form hydrogen and oxygen are chemical properties as the chemical composition of water changes in the given reaction.
Therefore the correct answer is b. 1 and 4
<span>Phosphorus pentoxide is a chemical compound with molecular formula P4O10 This white crystalline solid is the anhydride of phosphoric acid. It is a powerful desiccant and dehydrating agent.</span>
All are true except the statement that ions are formed by changing the number protons in an atom’s nucleus.
A neutral atom contains the same number of protons (positive charge) and electrons (negative charge).
If there are <em>more electrons than protons</em>, the atom becomes a <em>negative ion</em>.
If there are <em>fewer electrons than protons</em>, the atom becomes a <em>positive ion</em>.
The protons are in the nucleus, where we can’t easily get at them. The <em>electrons are outside the nucleus</em>, so other chemicals can easily get at them and either remove them or add to their number.
<em>Metals</em> have only a few valence electrons, so it is fairly easy to remove them and <em>form positive ions</em>.
