def cols_to_normalize(df, columns):
    """Convert data points to values between 0 and 1 and return new columns of prefixed data.
    
    Args: 
        df: Pandas dataframe.
        columns: List of columns to transform.

    Returns: 
        Original dataframe with additional prefixed columns.
    """
    for col in columns:
        df['norm_' + col] = (df[col] - df[col].min()) / (df[col].max() - df
            [col].min())
    return df
