Why does the mobile size heading become taller greens than the fuller sized web pages? Margin/padding issue, or other?

/*******************************
Heading
*******************************/

header {
  float: left;
  margin: 0 0 30px 0;
  padding: 50px 0 0 0;
  width: 100%;
}

#logo {
  text-align: center;
  margin: -20px;
}

h1  {
  font-family: 'Changa One', sans-serif;
  margin: 15px 0;
  font-size: 1.75em;
  font-weight: normal;
  line-height: 0.8em;
}

h2 {
  font-size: 0.75em;
  margin: -10px 0 0;
  font-weight: normal;
}


responsive.css

@media screen and (min-width: 480px) {

  /*******************************
  TWO COLUMN LAYOUT
  *******************************/

  #primary {
    width: 50%;
    float: left;
  }

  #secondary {
    width: 40%;
    float: right;
  }

  /*******************************
  PAGE: PORTFOLIO
  *******************************/

  #gallery li {
    width: 28.3333%;
  }

  #gallery li:nth-child(4n) {
    clear: left;
  }

  /*******************************
  PAGE: PORTFOLIO
  *******************************/

  .profile-photo {
    float: left;
    margin: 0 5% 80px 0;
  }

}

@media screen and (min-width: 660px) {

  /*******************************
  Header
  *******************************/

  nav {
    background: none;
    float: right;
    font-size: 1.125em;
    margin-right: 5%;
    text-align: right;
    width: 45%;
  }

  #logo {
    float: left;
    margin-left: 5%;
    text-align: left;
    width: 45%;
  }

  h1 {
    font-size: 2.5em;
  }

  h2 {
    font-size: 0.825em;
    margin-bottom: 20px;
  }

  header {
    border-bottom: 5px solid #599a68;
    margin-bottom: 60px;
  }


}