def word_splitter(df):
    """returns pandas DataFrame with a new column 'Split Tweets' that contains
        tweets as list of seperate words.
    
    Args:
        df (pandas(pd) DataFrame): pd.DataFrame object with atleast one column:
        'Tweets': Contains strings (pd.Series objects) of individual tweets (one tweet per value).
    Return:
           new pandas DataFrame with a new column:
           'Split Tweets':A list of seperate words, from *.split().
    """
    words = df['Tweets']
    df['Split Tweets'] = [word.lower().split() for word in words]
    return df