How do we know the time? A clock, a watch or a mobile phone can help us. However, many years ago there were no clocks and knowing the time was not so easy.
About 5, 500 years ago, the Egyptians invented the sun clock. This was a tall stone building. Its shadow (影子) showed the movement of the sun. So people were able to know midday. The Egyptians made a sundial about 3,500 years ago. It was smaller than the sun clock and could let people know the time for half a day. On cloudy days or at night it was impossible to tell the time with a sun clock or a sundial. Water clocks were the first clocks not to use the sun. The idea is simple. Water flows (流动) from one bottle to another. When the water reaches a certain level, it shows the hours. The Egyptians used water clocks about 3,400 years ago. These clocks were popular in the Middle East and China. But they failed to make people know the exact time.
In the 13th century, the mechanical clock was invented. This was more exact, but it was expensive to make one. Over the next few centuries it was developed. For example, springs(发条) were added. This enabled people to get the correct time and allowed clocks to be smaller. In 1927, the first quartz clock was developed. Clocks became cheaper to build. It's also cheaper for ordinary people to own a clock. People began depending on them more and more to run businesses, markets and so on. More recently, in 1956, came the digital clock. And
nowadays satellites send our mobile phones the time to the exact second.
There has been a lot of progress in timekeeping. Clocks are always changing but some things never change.
1. What does the word "ordinary" in Paragraph 3 mean in Chinese?| A．现代的 | B．特殊的 | C．普通的 |
| A．Four. | B．Five. | C．Six. |
A．  |
B． |
C．  |
| A．The importance of time. |
| B．The inventions of clocks. |
| C．The development of timekeeping. |
2 . ①Chemistry is everywhere in our daily life. Sometimes it's easy to see. At other times, it can be very hard to see the everyday chemistry at work, but nearly everything you touch has some chemicals (化学物质) in it.
②Chemistry helps to make products for use. Something as simple as toothpaste has at least three chemicals that keep your teeth clean. Other things in your daily life are created by chemistry, such as hair products and soap. Without chemistry, we would never have known that we need soap to get the oil out of clothes.
③Chemistry also helps us understand the world around us. Thanks to chemistry, we know bleach (漂白剂) can't be mixed with vinegar (醋), because the mixture can produce harmful gas.
④Chemistry plays a big role in food preparation. Cooking food causes it to go through a chemical change. That is the reason why cooked food often tastes different from uncooked food. Too much or too little of any chemical material makes a difference to the result of baking (烘焙). For example, the cake can be too soft or too hard.
⑤Chemistry isn't something that just lives in a laboratory; it's something that you meet hundreds of times in life. Knowing how chemistry works will give you a greater understanding of the life.
1. What can the chemistry in soap help us?| A．To clean the teeth. | B．To make the teeth strong. |
| C．To clean the oil off clothes. | D．To make the clothes new. |
| A．we can mix bleach with vinegar | B．the mixture can produce useful gas |
| C．we can't mix bleach with vinegar | D．chemistry can't help us make products |
| A．cooked food is much better than uncooked food |
| B．chemistry plays a big role in food preparation |
| C．there are no chemical changes while we are cooking |
| D．the cake can't be too soft or too hard with chemistry |
A． | B． | C． | D． |
| A．Chemistry and food. | B．Chemistry around the world. |
| C．Chemistry and products. | D．Chemistry in everyday life. |
