题目

质量是21.6 g的蜡块体积是24 cm3 ，蜡块的密度是______kg /m 3；将这蜡块切掉一半，剩下半块蜡的质量是__________，密度是__________kg /m 3。 答案：【答案】0.910310.8g0.9103【解析】蜡块的密度：ρ＝＝0.9g/cm3＝0.9×103kg/m3，因密度是物质的一种特性，其大小与物体的体积和质量没有关系，所以，将这蜡块切掉一半，剩下半块蜡的质量变为原来的一半，密度不变。故剩下半块蜡的质量是＝10.8g，密度仍是0.9×103kg /m 3。   Modern science now agrees that among all lifestyle reasons,no single reason is more important to our health than the food we eat. The Healthiest Way of Eating is eating for the most nutrition (营养品) and enjoyment. Eating is one of the few things we do every single day. And since most of us eat 3 or more meals a day,we are eating over 1 ,000 meals a year!That means we have the opportunity to make 1 ,000 healthy decisions each year to positively affect our health. The Healthiest Way of Eating is designed to help you make decisions that will keep good health. And it can be done in 3 easy steps：   Choose healthier,nutrient-rich World's Healthiest Foods   Combine (结合) them in the Healthiest Way of Eating Plan to finish your nutritional needs    Use cooking plans that keep maximum nutrition and tastes    The Healthiest Way of Eating is not only for those for whom eating is a reaction to “hunger” but for those who want to eat for nourishment and better health. This new Healthiest Way of Eating goes far beyond taking in calories to satisfy your hunger;it is a way to enjoy foods that will nourish your body. If you want to eat more healthily,the Healthiest Way of Eating does all the work for you by taking out all of the guesswork and making it creative,fun,easy,and enjoyable. We could be saving millions of lives and several hundred billion dollars in healthcare costs related to obesity,diabetes,heart disease,and cancer if we would eat more health-promoting,nutrient-rich foods.() 1. How many steps should we do to keep good health?   A. 3.   B. 4.   C. 1,000.   D. 1.() 2. What can help us make decisions that will keep good health?   A. Choose healthier,nutrient-rich World's Healthiest Foods.   B. The healthiest way of eating.   C. Use cooking plans.   D. Combine them in the Healthiest Way of Eating Plan to finish your nutritional needs.() 3. What do you think of the Healthiest Way of Eating?   A. A book. B. A way.   C. A games. D. An article.() 4. What would be saved if we would eat more health-promoting,nutrient-rich foods?   A. Medical.   B. Money.   C. Millions of lives and several hundred billion dollars.   D. Meals.