Hand warmers are small (sometimes disposable) packets which are held in the hand and produce heat on demand to warm cold hands. They are commonly used in outdoor activities such as hiking and skiing to keep the extremities warm and assist insulated clothing. Other types of warmers are available to provide soothing heat for muscular or joint aches. Some hand warmers contain cellulose, iron, water, activated carbon, vermiculite and salt and produce heat from the exothermic oxidisation of iron when exposed to air. A second type generate heat through exothermic crystallisation of supercooled molten materials (usually sodium acetate) and are reusable. These can be recharged by boiling the warmers and allowing them to cool. Heating of the pads is triggered by snapping a small metal device buried in the pad which generates shock waves to initiate crystallisation. A third type uses lighter fluid (lighter fuel) or LPG which is reacted with a platinum catalyst to release heat by oxidation reactions. These can be used on many occasions by simply refuelling. Depending on the type and the source of heat, hand warmers last between 30 minutes (recrystallisation) though to 12 - 24 hours.
two
fizzing, bubbling, gas, odors, a new substance always is formed once a chemical reaction takes place. but it depends on what is being reacted to determine what reaction is going to take place.
It is a physical change. The sodium hydroxide dissolves, but it is still sodium hydroxide.
Chemical reactions take place in various cell organelles. For example, in mitochondria, reactions like cellular respiration occur to produce energy. In the nucleus, reactions like DNA replication and transcription occur. And in the cytoplasm, reactions like protein synthesis take place.
When a chemical reaction takes place, it starts with chemicals which are called reactants, literally meaning those which react, and after the reaction has taken place you then have chemicals called products, because they were produced by the reaction.
The valence electrons are the part that takes place in a chemical reaction.
chemical reaction takes place in rancidity
These initial substances are the reactants.
NaHCO3
reactant
When a chemical reaction takes place, the compound formed is called the product. The product is the end result of the chemical reaction, typically formed from the reactants that underwent a rearrangement of atoms.
Rusting is an oxydation reaction.
bonds
Yes.
no
The volume is changed.
combustion