Step 1: Understand the nature of the transaction. The purchase of office supplies for \$500 cash means the company is acquiring office supplies and paying for them immediately using cash.
Step 2: Identify the accounts involved. The two accounts affected are 'Office Supplies' (an asset account) and 'Cash' (another asset account).
Step 3: Determine the impact on each account. Since office supplies are being acquired, the 'Office Supplies' account will increase (debit). Since cash is being used to pay, the 'Cash' account will decrease (credit).
Step 4: Apply the rules of double-entry accounting. In double-entry accounting, every transaction must have at least one debit and one credit entry, and the total debits must equal the total credits.
Step 5: Write the journal entry. Debit 'Office Supplies' for \$500 to reflect the increase in supplies, and credit 'Cash' for \$500 to reflect the decrease in cash.