When molecular hydrogen (H2) and oxygen (O2) are combined and allowed to react together, energy is released and the molecules of hydrogen and oxygen can combine to form either water or hydrogen peroxide. These two processes are represented by the two chemical equations shown at right.

Hydrogen is a colourless gas, H2, that is lighter than air. Mixtures of hydrogen gas and air do not react unless ignited with a flame or spark, in which case the result is a fire or explosion with a characteristic reddish flame whose only products are water, H2O.

The hydrogen mixes with oxygen in the air forming an explosive mixture. Because the hydrogen and oxygen must mix before an explosion can occur, the explosion is relatively slow and diffuse.

Since the weight of hydrogen is less than air, it rises in the atmosphere and is therefore rarely found in its pure form, H2. In a flame of pure hydrogen gas, burning in air, the hydrogen (H2) reacts with oxygen (O2) to form water (H2O) and releases energy.

Hydrogen has the highest calorific value so it can be considered as the best fuel but it is highly inflammable so it is diificult to store, transport and handle so it is used as a fuel only where it is absolutely necessary.

Yes, the equation is balanced. There are the same number of Hydrogen (H) and Oxygen (O) atoms on both sides of the equation.

Because each water molecule, H2O, contains only one oxygen atom, two water molecules must form for each oxygen molecule that reacts. The coefficient 2 in front of the H2O(l ) makes this clear. Water is H2O, whereas H2O2 is hydrogen peroxide, a very different substance from water.

A combustion reaction is a reaction in which a substance reacts with oxygen gas, releasing energy in the form of light and heat. Combustion reactions must involve O2 as one reactant. The combustion of hydrogen gas produces water vapor. Notice that this reaction also qualifies as a combination reaction.

water

oxidation reaction

The synthesis (forming) of water (H2O) from hydrogen gas (H2) and oxygen gas (O2) is another example of chemical change. A simplified diagram of this reaction is shown in Figure 13.3. The chemical bonds between O in O2 and between H in H2 are broken and new bonds between H and O (to form H2O) are formed.

For instance, when an electric current is passed through water (H2O), it can be broken down into hydrogen and oxygen or H2 + O2. In this example, water is broken down into its two elements. The result is a chemical change because the starting and ending molecules are different.

(1) Ammonia is composed of one nitrogen and three hydrogen atoms so it is a compound. Therefore it can be broken down by chemical change.

Splitting carbon dioxide (CO2) into carbon and oxygen can in fact be accomplished, but there is a catch: doing so requires energy. Consider the proposal as a chemical reaction: CO2 plus energy yields carbon and oxygen. This formula essentially reverses coal combustion (carbon plus oxygen yields CO2 and energy).

NASA has developed a new technology that can convert the greenhouse gas carbon dioxide (C02) into fuel by using solar-powered, thin-film devices. Metal oxide thin films are fabricated to produce a photoelectrochemical cell that is powered by solar energy.

Microscopic view of the atoms of the element argon (gas phase). consists of only one kind of atom, cannot be broken down into a simpler type of matter by either physical or chemical means, and. can exist as either atoms (e.g. argon) or molecules (e.g., nitrogen).

Boiling waterBoiling water is an example of a physical change and not a chemical change because the water vapor still has the same molecular structure as liquid water (H2O).

Answer and Explanation: No, boiling water is NOT a chemical reaction, but it is a physical change. When water, H2 O, is in liquid form, it can be heated to a boil.

Examples of Chemical Change in Everyday Life

• Burning of paper and log of wood.
• Digestion of food.
• Boiling an egg.
• Chemical battery usage.
• Electroplating a metal.
• Baking a cake.
• Milk going sour.
• Various metabolic reactions that take place in the cells.

Examples: iron and oxygen combining to make rust. vinegar and baking soda combining to make sodium acetate, carbon dioxide and water. things burning or exploding.

The correct answer is burning of paper. Therefore, burning of a paper is an example of chemical change. The concept of chemical changes can be explained as changes that take place on the molecular level as the result of a chemical reaction, and as such, a new substance is produced.

Examples of physical change include changes in the size or shape of matter. Changes of state—for example, from solid to liquid or from liquid to gas—are also physical changes. Some of the processes that cause physical changes include cutting, bending, dissolving, freezing, boiling, and melting.

c) Drying of clothes: It occurs through a process called evaporation. It is not a chemical change since the drying of clothes does not lead to a change in the chemical composition of the clothes and hence does not change its chemical properties.

A change can’t be both physical and chemical, but physical and chemical changes can occur simultaneously. This is what’s happening with the burning candle: the wax is melting, which is a physical change, and it’s combusting, which is a chemical change.