To change grams to moles and vice versa in chemistry, it helps to know what molar mass is.

Molar mass is the weight of one mole of a substance. It is usually shown in grams per mole (g/mol). Each element has its own molar mass, and you can find these numbers on the periodic table.

Here are the simple steps for the conversion:

1. Finding Molar Mass:

   • To find the molar mass of a substance, you add together the weights of all the atoms in it.
   • For example, let’s look at water (H₂O):
     • Hydrogen (H) = 1 g/mol, and there are 2 hydrogen atoms → $2 \times 1 = 2$ g/mol
     • Oxygen (O) = 16 g/mol
     • So, the total molar mass of H₂O = $2 + 16 = 18$ g/mol

2. Converting Grams to Moles:

   • You can use this equation: $\text{Moles} = \frac{\text{grams}}{\text{molar mass}}$
   • For example, if you have 36 grams of H₂O, here’s how you calculate it: $\text{Moles} = \frac{36 \text{ g}}{18 \text{ g/mol}} = 2 \text{ moles}$

3. Converting Moles to Grams:

   • You can use this equation: $\text{Grams} = \text{moles} \times \text{molar mass}$
   • For 3 moles of H₂O, it looks like this: $\text{Grams} = 3 \text{ moles} \times 18 \text{ g/mol} = 54 \text{ g}$

By following these steps, you can easily switch between grams and moles!