Use plastic pellets or marbles to represent water in the solid state. What do you need to do to the pellets to represent the change from solid to liquid?
Chemical changes in matter
When a
chemical change takes place, new substances are formed in a chemical reaction. These new products may have very different properties from the substances that were there at the start of the reaction.
The breakdown of copper (II) chloride to form copper and chlorine is an example of chemical change. A simplified diagram of this reaction is shown in
[link] . In this reaction, the initial substance is copper (II) chloride, but once the reaction is complete, the products are copper and chlorine.
The decomposition of copper(II) chloride to form copper and chlorine. We write this as:
Chemical change
The formation of new substances in a chemical reaction. One type of matter is changed into something different.
There are some important things to remember about chemical changes:
Arrangement of particles During a chemical change, the particles themselves are changed in some way. In the example of copper (II) chloride that was used earlier, the
molecules were split up into their component atoms. The number of particles will change because each
molecule breaks down into one copper atom (
) and one chlorine molecule (
). However, what you should have noticed, is that the number of atoms of each element stays the same, as does the total mass of the atoms. This will be discussed in more detail in a later section.
Energy changes The energy changes that take place during a chemical reaction are much greater than those that take place during a physical change in matter. During a chemical reaction, energy is used up in order to break bonds, and then energy is released when the new product is formed. This will be discussed in more detail in
"Energy changes in chemical reactions" .
Reversibility Chemical changes are far more difficult to reverse than physical changes.
We will consider two types of chemical reactions:
decomposition reactions and
synthesis reactions .
Decomposition reactions
A
decomposition reaction occurs when a chemical compound is broken down into elements or smaller compounds. The generalised equation for a decomposition reaction is:
One example of such a reaction is the decomposition of mercury (II) oxide (
[link] ) to form mercury and oxygen according to the following equation:
The decomposition of
to form
and
The decomposition of hydrogen peroxide is another example.
Experiment : the decomposition of hydrogen peroxide
Aim:
To observe the decomposition of hydrogen peroxide when it is heated.
Apparatus:
Dilute hydrogen peroxide (about 3%); manganese dioxide; test tubes; a water bowl; stopper and delivery tube
Hydrogen peroxide can cause chemical burns. Work carefully with it.
Method:
Put a small amount (about 5 ml) of hydrogen peroxide in a test tube.
Bacteria doesn't produce energy they are dependent upon their substrate in case of lack of nutrients they are able to make spores which helps them to sustain in harsh environments
_Adnan
But not all bacteria make spores, l mean Eukaryotic cells have Mitochondria which acts as powerhouse for them, since bacteria don't have it, what is the substitution for it?
Assimilatory nitrate reduction is a process that occurs in some microorganisms, such as bacteria and archaea, in which nitrate (NO3-) is reduced to nitrite (NO2-), and then further reduced to ammonia (NH3).
Elkana
This process is called assimilatory nitrate reduction because the nitrogen that is produced is incorporated in the cells of microorganisms where it can be used in the synthesis of amino acids and other nitrogen products
There are nothing like emergency disease but there are some common medical emergency which can occur simultaneously like Bleeding,heart attack,Breathing difficulties,severe pain heart stock.Hope you will get my point .Have a nice day ❣️
_Adnan
define infection ,prevention and control
Innocent
I think infection prevention and control is the avoidance of all things we do that gives out break of infections and promotion of health practices that promote life
