"Dreams (梦 ) may be more important than sleep. We all need to dream，" some scientists say.

    Dreams take up about one quarter of our ____(sleep) time. People have several dreams each night. Dreams are ____ short films. They are usually in color. Some dreams are like old films. They come to us over ____ over again. That may be because the dreamer is ____(worry) about something. Dreaming may be a way of trying to find an answer.

    Some people get new ideas about their work ____ dreams. They may have been thinking about their work all day. These ____(think) can carry over into dreams.

    Sometimes, we wake up with a good ____(feel) from a dream. But often we can't remember the dream. Dreams can disappear (消失) ____(quick) from memory (记忆).

    Too much dreaming can be harmful (有害的). The ____(much) we sleep， the longer we dream. The mind is hard at work when we dream. That is ____ we may have a long sleep and still wake up tired.

进行实验室温下，选用20mL不同溶质质量分数的盐酸(4%和6%)分别与1g颗粒状或块状的石灰石进行实验(固定夹持仪器略去)。