QUES: Chemical changes produce new substances. For this reason, they often cannot be undone. Some chemical changes can be reversed, sort of. To do so requires another chemical change to take place. For example, you can undo the tarnish on copper pennies by placing them in vinegar. The acid in the vinegar reacts with the tarnish. This is a chemical change that makes the pennies bright and shiny again. You can try this yourself at home to see how well it works. Other chemical changes cannot be reversed at all or may be difficult to do. Rusting is a chemical change. If metal rusts, the best you can do is to sand off the rust to get down to the shiny metal. Although the metal may now be shiny, the rust was removed. The rust was not changed back into the original metal. Some chemical reactions occur in only one direction. These reactions are called irreversible reactions. For example, you cannot change a fried egg back into a raw egg. Can you think of some other irreversible reactions related to cooking? Would you like a piece of cake?
Do you have any questions?
MY QUESTION: Can chemical changes be undone?

QUES: (CNN) -- Beyond skateboards, Silicon Valley and hippies, California has a trendsetting streak of a different kind. The state has been first to pass major public health initiatives that have spread throughout the country. California was first to require smog checks for clean air, pass anti-tobacco initiatives and bike helmets laws. While these laws were met with skepticism and ridicule, they've often become standard practice in other states. The Golden State was first to ban smoking in workplaces, bars and restaurants in 1998. Now similar rules exist throughout the country. Some advocates tout the state as a forward-thinking vanguard in which its health and safety laws are routinely emulated by other states. "There have been progressive legislations in tobacco, environment and obesity prevention," said Mark Horton, a lecturer at the University of California Berkeley School of Public Health. "In some respect, the rest of the country looks to California as a laboratory for moving forward with those various types of initiatives." But some critics liken the Golden State to a nanny state. California has 151,002 health and safety laws. "It never ends," said Laer Pearce, who works in public affairs in Orange County. "Every year, several hundred bills come through and dozens of them tell us how to live our lives." Starting in January, 760 new California laws went into effect -- for example, the importing of shark fins is prohibited, student athletes are required to have medical clearance after suffering a head injury, teens are banned from using tanning booths and the sale of caffeinated beer is forbidden. There's a perception that California has "more folks who are health-oriented and more health-minded," said Horton, former director of the California Department of Public Health. It's not just workout fanatics hanging out at Muscle Beach, Sierra Club members hiking mountains or the uber-health-conscious touting organic foods. Californians in general tend to have healthier habits, ranking 10th for physical activity, fourth for healthy blood pressure and fifth for a diet high in fruits and vegetables compared with other states, according to America's Health Rankings.
Do you have any questions?
MY QUESTION: Why do some critics call California the nanny state?

QUES: Late on the next Sunday afternoon Gifford had gone for a country walk which he had arranged to bring him round in time for the evening service at the little village church of Wynford standing just outside the park boundary. His way took him by well-remembered field-paths which, although towards the end of his walk darkness had set in, he had no difficulty in tracing. The last field he crossed brought him to a by-road joining the highway which ran through Wynford, the junction being about a quarter of a mile from the church. As he neared the stile which admitted to the road he saw, on the other side of the hedge and showing just above it, the head of a man. At the sound of his footsteps the man quickly turned, and, as for a moment the fitful moonlight caught his face, Gifford was sure he recognized Gervase Henshaw. But he took no notice and kept on his way to the stile, which he crossed and gained the road. As he did so he glanced back. A horse and trap was waiting there with Henshaw in it. He was now bending down, probably with the object of concealing his identity, and had moved on a few paces farther down the road.
Do you have any questions?
MY QUESTION: Nearing the stile who did Gifford see?

QUES: (CNN) -- Jo-Wilfried Tsonga ended Roger Federer's hopes of winning a record-equaling seventh Wimbledon title on Wednesday as the French 12th seed staged a stunning fightback to reach the semifinals. Federer appeared to be cruising into the last four after winning the first two sets, but Tsonga inflicted the Swiss world No. 3's first defeat from that vantage point in 179 grand slam matches. It was only the third time in the 29-year-old's glittering career that the 16-time grand slam champion had surrendered a two-set lead. Tsonga, ranked 19th in the world, triumphed 3-6 6-7 (3-7) 6-4 6-4 6-4 on Centre Court, serving out to love as he earned a clash with second seed Novak Djokovic. The Serbian, who beat Tsonga in the 2008 Australian Open final, ended the dream run of Australian 18-year-old Bernard Tomic. Tsonga defeated Federer for just the second time in six meetings, their first on grass. "It was amazing. I played unbelievable. It's never easy to come back against Roger. I'm so happy, it's crazy," the 26-year-old told reporters after reaching the semifinals at Wimbledon for the first time. "He's the biggest champion in the sport. He has achieved so much and is the best player in the world. To be two sets down and come back was unbelievable. I served really well. Against Djokovic I will have to come out and do the same again." Federer has now lost in the quarterfinals two years in a row, being beaten by eventual runner-up Tomas Berdych in 2010. "Jo played great. Really from start to finish I don't remember seeing a break point after I broke him in the first game," Federer said.
Do you have any questions?
MY QUESTION:
Who was the tennis player that beat Federer?