This article will teach you how to block Facebook on computers that only use Google Chrome. To do this you can use the Block Site extension or the Nanny extension. These are both free for Chrome. You cannot block Facebook in the Google Chrome mobile app.
Steps
Method 1 of 2: Using Block Site

Step 1. Go to Block Site extension page
This will bring up the Block Site window.

Step #2. Click on + ADD TO CHROME
It's a blue button in the top right corner of the Block Site window.

Step #3. Click Add Extension when prompted
This will install the Block Site extension.

Step 4. Refresh Chrome
Click "⟳" in the top left corner of the Chrome window. This will refresh Chrome and place the Block Site icon in the top right corner of the Chrome browser.

Step 5. Click on the Block Site icon
This looks like a 'www' with a circle and a line through it. You'll find this on the right side of the Chrome window. This will cause a pull-out menu to appear.

Step 6. Click on Options
This option is located in Block Site's pull-down menu. A new tab with the Block Site settings will appear.

Step 7. Enter the address of Facebook
Type in the 'Add Page' text box. You'll find this text box at the top of the page.

Step 8. Click Add Page
It's a green button to the right of the "Add page" text box. This will put Facebook on Block Site's blocked list. When a user tries to access Facebook, Block Site will redirect them to another page.
You can add a second address (e.g. https://www.google.com/ in the 'Forward to' text field next to Facebook's address so that this address will be opened when someone tries to access Facebook

Step 9. Click on Exit
This is a blue button at the bottom of the page. This will close Block Site. Facebook will remain blocked until you unblock it.
Method 2 of 2: Using Nanny

Step #1. Open Nanny's extension page
This will bring up Nanny's window.

Step #2. Click on + ADD TO CHROME
It's a blue button in the top right corner of the Nanny screen.

Step #3. Click Add Extension when prompted
This will install the Nanny extension.

Step 4. Right click on the Nanny icon
You'll find this in the top-right corner of the Chrome window. Right-clicking on this icon will bring up a pull-down menu.
- If your computer doesn't have a right mouse button, you can tap with two fingers instead of right-clicking.
- On a Mac, you can press Control and click the icon instead.

Step 5. Click Options
This option is located at the top of the slide-out menu. This will open the Nanny page.

Step 6. Click on the Blocked URLs tab
This is located at the top left of the page.

Step 7. Enter a name for your list of blocked URLs
Type a name in the "Block Set Name" field at the top of the page.
Since you're just blocking Facebook, consider calling it "Social Media" or "Facebook Only."

Step 8. Enter the address of Facebook
Type in the "URLs" field.

Step 9. Set a block time
Type the start time and end time in the 'Block Time' text box and choose the 12-hour format.
For example, to block from 11am to 5pm and from 9pm to 8am, you would type 1100-1700, 2100-0800

Step 10. Make sure all days are checked
In the 'Apply to Days' row, make sure that every day of the week on which you want to block Facebook is checked.

Step 11. Click Set URL
You'll find this in the bottom-left corner of the page. This will save you the settings and block Facebook for the selected time frame.