Option Explicit
Option Base 1
Sub CKKeywords()
Dim c As Range, a As Long, b As Long
Dim MyKeys As Variant
Application.ScreenUpdating = False
MyKeys = Sheets("Keywords").Range("A2:A" & Sheets("Keywords").Cells(Rows.Count, 1).End(xlUp).Row)
With Sheets("Sheet1")
  For Each c In .Range("C1", .Range("C" & Rows.Count).End(xlUp))
    For a = LBound(MyKeys) To UBound(MyKeys)
      b = 0
      On Error Resume Next
      b = WorksheetFunction.Find(Trim(MyKeys(a, 1)), c, 1)
      On Error GoTo 0
      If b > 0 Then
        c.Offset(, 1) = "Yes"
        Exit For
      End If
    Next a
  Next c
End With
Application.ScreenUpdating = True
End Sub

With Sheets("Sheet1")
  For Each c In .Range("C1", .Range("C" & Rows.Count).End(xlUp))