Because atoms of different elements react with one another in very specific proportions but atoms of different elements have different weights, chemists often describe the amount of different elements and compounds in terms of the number of "moles". A "mole" of any element contains the same number of atoms: 602,214,150,000,000,000,000,000 atoms. The atomic mass of an element can be used to see how much of the element makes a mole. For example, the atomic mass of copper is about 63.55. That means about 63.55 grams of copper metal has a mole of atoms. The atomic mass of chlorine is about 35.45. That means 35.45 grams of chlorine has a mole of atoms in it.
Moles can be used to see how many molecules are in chemical compounds, too. Copper(II) chloride is an example. CuCl is its chemical formula. There is one copper atom (63.55) and two chlorine atoms (35.45 · 2 = 70.90). Add all the molar masses of the elements together to get the molar mass of the chemical compound (63.55 + 70.90 = 134.45). That means in 134.45 grams of copper(II) chloride, there is one mole of copper(II) chloride molecules. This concept is used to calculate how much chemicals are needed in a chemical reaction if no reactants (chemicals that are reacted) should be left. If too much reactant is used, there will be some reactants left in the chemical reaction.
Acids and bases are common chemicals. Acids release H ions when in water, and bases release OH ions when in water. Acids can react with bases. The H ion is taken from the acid by the base. This makes water, HO. A salt is also made when an acid and a base react together. An example would be reacting hydrochloric acid (HCl) and sodium hydroxide (NaOH). Hydrochloric acid releases H and Cl ions in water. The base releases Na and OH ions. The H and the OH react to make water. There is a solution of sodium chloride (NaCl) left. Sodium chloride is a salt.
Chemistry is very useful in everyday life and makes up the foundation of many branches of science. Most objects are made by chemists (people who do chemistry). Chemists are constantly working to find new and useful substances. Chemists make new drugs and materials like paints that we use every day.
Many chemicals are harmless, but there are some chemicals that are dangerous. For example, mercury(II) chloride is very toxic. Chromates can cause cancer. Tin(II) chloride pollutes water easily. Hydrochloric acid can cause bad burns. Some chemicals like hydrogen can explode or catch fire. To stay safe, chemists experiment with chemicals in a chemical lab. They use special equipment and clothing to do reactions and keep the chemicals contained. The chemicals used in drugs and in things like bleach have been tested to make sure they are safe if used correctly.
Compound
Computer science
Computer science is the study of manipulating, managing, transforming and encoding information.
There are many different areas in computer science. Some areas consider problems in an abstract manner, while some need special machines, called computers.
A person who works with computers will often need mathematics, science, and logic in order to design and work with computers.
This is so people can find new and easier ways to do things, and the way to approach problems with this information.
While computers can do some things easily (like simple math, or sorting out a list of names from A-to-Z), computers cannot answer questions when there is not enough information, or when there is no real answer. Also, computers may take too much time to finish long tasks. For example, it may take too long to find the shortest way through all of the towns in the USA - so instead a computer will try to make a close guess. A computer will answer these simpler questions much faster.
Algorithms are a specific set of instructions or steps on how to complete a task. For example, a computer scientist wants to sort playing cards. There are many ways to sort them - by suits (diamonds, clubs, hearts, and spades) or by numbers (2, 3, 4, 5, 6, 7, 8, 9, 10, Jack, Queen, King, and Ace). By deciding on a set of steps to sort the cards, the scientist has created an algorithm. The scientist then needs to test whether this algorithm works. This shows how well and how fast the algorithm sorts cards.
A simple but slow algorithm is: pick up two cards and check whether they are sorted correctly. If they are not, reverse them. Then do it again with another two, and repeat them all until they are all sorted. This "bubble sort" method will work, but it will take a very long time.
A better algorithm is: find the first card with the smallest suit and smallest number (2 of diamonds), and place it at the start. After this, look for the second card, and so on. This algorithm is much faster, and does not need much space. This algorithm is a "selection sort".
Ada Lovelace wrote the first computer algorithm in 1843, for a computer that was never finished. Computers began during World War II. Computer science separated from the other sciences during the 1960s and 1970s. Now, computer science has its own methods, and has its own technical terms. It is related to electrical engineering, mathematics, and language science.
Computer science looks at the theoretical parts of computers. Computer engineering looks at the physical parts of computers (hardware). Software engineering looks at the use of computer programs and how to make them.
Computer
A computer is a machine that uses electronics to input, process, and then output data. Input of data means to read information from a keyboard, a storage device like a hard drive, or a sensor. The computer processes or changes the data by following the instructions in software programs. A program is a list the steps for doing arithmetic, comparing data, and rearranging data. The data is then saved in a storage device, shown on a display, or sent to another computer. Computers can be connected together to form a network such as the internet, allowing the computers to communicate with each other.
The processor of a computer is made from integrated circuits (chips) that contains many transistors. Most computers are digital, which means that they represent information by using binary digits, or bits. Computers come in different shapes and sizes, depending on the brand and model and purpose. They range from small computers such as smartphones and laptops, to large computers such as supercomputers.
The two important parts of a computer are: It responds to a specific instruction set in a well-defined manner and it can execute a stored list of instructions called a program. There are four main actions in a computer: inputting, storing, outputting and processing.
Modern computers can do billions of calculations in a second. Being able to calculate many times per second allows modern computers to multi-task, which means they can do many different tasks at the same time. Computers do many different jobs where automation is useful. Some examples are controlling traffic lights, vehicles , security systems, washing machines and digital televisions.
Computers can be designed to do almost anything with information. Computers are used to control large and small machines which in the past were controlled by humans. Most people have used a personal computer in their home or at work. They are used for things such as calculation, listening to music, reading an article, writing etc.
Modern computers are electronic computer hardware. They do mathematical arithmetic very quickly but computers do not really "think". They only follow the instructions in their software programs. The software uses the hardware when the user gives it instructions, and gives useful outputs.
Computers are controlled with user interfaces. Input devices which include keyboards, computer mice, buttons, and touch screens, etc.