Is 2oh−+ca2+−> 2ca(oh)2 balanced

No.

Explanation:

No.  There is 1 atom of Ca on the left and 2 Ca's on the right  and 2 OH's on the left and 4 on the right.

The balanced equation is:

4OH-  +  2Ca2+ >  2Ca(OH)2.

Is not balanced

Explanation:

For an equation to be balanced there must be on each side of the equation the same amount of each atom.

2 OH−  +  Ca 2+   > 2 Ca(OH)2

On the left we have the following amounts of atoms:

Ca = 1

O = 2

H = 2

Total charges =  0

And on the right:

Ca = 2

O = 4

H = 4

Total charges =  0

We can see that on the right we have twice as many atoms as on the left, so we can delete a molecule of Ca(OH)2

                         2 OH−  +  Ca 2+   >  Ca(OH)2

Now the equation is balanced because there are the same number of atoms on both sides and also the charges are equal in both sides.

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.

1. they vary with a higher number because boiling is way hotter than melting