Match the vocabulary word with its definition. 1 . radioactive waste cyclical migration 2 . the regular, periodic movement of people between places demographics 3 . the study of population fallout 4 . a substance that prevents evaporation or erosion fertility rate 5 . a fertile area in a desert mulch 6 . land on the leeward side of a mountain oasis 7 . the number of children a woman will have on an average peat 8 . land below sea level polder 9 . decomposed organic material population density 10 . the number of people who live in a particular area rain shadow

Cyclical migration: It is the regular, periodic movement of people between places. Example of a cyclical migration pattern is the repeated travel done by a worker from the office to his/her house and vice versa. 

Demographics: It is the study of human population and certain groups of people within it. It is based on certain factors such as age, race, gender, etc. 

Fallout: It is a radioactive waste produced from nuclear explosions that enters the atmosphere which eventually falls back in the form of dust or precipitates. This radioactive waste is dangerous to human health because it damages the DNA, causing  cells to mutate.

Fertility Rate: It is the number of children a woman will give
birth to on average. It is important to get the fertility rate of women to be able to predict the population growth of a certain community or country.

Mulch: It is a substance that prevents evaporation or erosion which is commonly applied on the surface of the soil. It also minimizes the growth of unwanted plants or weeds and  enhances the aesthetic appeal of the land.

Oasis: It is a fertile area in a desert. It is characterized by the presence of a pond or natural spring which provides food and habitat for desert animals and humans. In the past, oases served as restocking points for trade caravans travelling in the desert. 

Peat: It is a partially decomposed organic material commonly made of plants. In some countries such as Ireland and Scotland, peat is used as a fuel. It used for cooking and heating for houses. 

Polder: It is the land below the sea level. It is a piece of land that was once part of a body of water which was reclaimed through the construction of drainages. Polders are essential for controlling floods.  

Population Density: It is the number of people who live in a particular area. It is a key factor in business planning because it allows people to choose a location which is easily accessible with the most number of residents. 

Rain Shadow: It is the land on the leeward side of a mountain. The mountain serves as a wall which blocks the pathway of rain-producing systems, creating a "shadow" where the land is dry.

So  if  the sum of the enthalpies of the reactants is greater than the products, the  reaction  will be  exothermic.  if  the products side has a larger enthalpy, the  reaction  is  endothermic. you may wonder why  endothermic reactions, which soak up energy or enthalpy from the environment, even happen