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understand the Law of Conservation of Mass. I will also learn the signs that indicate a chemical reaction has HAPPENED and that there are FIVE different types of chemical reactions!!
understand the Law of Conservation of Mass. I will also learn the signs that indicate a chemical reaction has HAPPENED and that there are FIVE different types of chemical reactions!!
KEYWORDS: Law of Conservation of Mass, precipitate, synthesis, decomposition, single replacement, double replacement, combustion
"Chemistry is about making and breaking chemical bonds, a chaotic dance where atomic partners are swapped. But the problem is that we cannot see this frenetic molecular level activity with our own eyes. We see macroscopic changes such as bubbles, a colour change, perhaps a spark of light, or glimpse the appearance or disappearance of a solid"
copyright to Potions for Muggles
Following on from atoms and elements..
As elements bond together compounds are created.
This involves a chemical reaction.
How do we know if a chemical reaction has taken place?
Chemical changes indicate
a chemical reaction has taken place!
If we observe physical changes only =
NO chemical reaction.
So, what are chemical and physical changes?
CHEM 9.29 - Chemical & Physical Changes
The simplest way to describe a chemical reaction is to say that starting substances are converted into new substances.
Chemical changes cause the atoms in the substance to rearrange and form new substances. Evidence this has happened includes:
There is a permanent colour change
A gas is released (bubbles or smell)
A new substance is formed
Heat is absorbed or released
A solid is formed (a precipitate)
Sound or light is given off
There is a rule in science that states that
the amount of matter (stuff) at the start of a chemical reaction will equal the amount of matter (stuff) at the end of the chemical reaction.
This is the "Law of Conservation of Mass".
It says "Mass cannot be created nor destroyed"
Watch here below!
We will study FIVE types of chemical reactions in Yr 9.
Watch below for an introduction...
Five types of chemical reactions you need to know!
1. Synthesis Reaction: two or more substances are combined
to make a single product
MAKING!
2. Decomposition Reaction: One substance breaks down into two or more substances.
BREAKING!
3. Single Replacement Reaction: When one element replaces another in a compound.
SINGLE SWAP!
4. A Double Replacement Reaction: The ion from one compound replaces the ion from another compound to form two new compounds.
DOUBLE SWAP!
5. Combustion Reaction: When a substance reacts with oxygen to produce energy in the form of heat or light. It releases carbon dioxide and water as products
BUST!
CHEM 9.30 - Chemical reaction types -
(COMBUSTION IS OMITTED FROM THIS SHEET AS IT HAS OXYGEN AS A REACTANT, SEE BELOW)
CHEM 9.30 - chemical-reaction-types.pdf understand recognise and experience 'Decomposition' and 'Single Replacement' first hand, in the lab.
understand recognise and experience 'Decomposition' and 'Single Replacement' first hand, in the lab.
KEYWORDS: Decomposition, single replacement,
Let's have a look in more detail..
1. Synthesis Reaction:
Two or more substances are combined to make a single product.
MAKING!
WHAT IS HAPPENING ?
elements are joined together
EXAMPLES...
hydrogen and oxygen -----> water
hydrogen (H2) and oxygen (O2) forms water (2H2O) - New product!
We know a chemical reaction has occurred as new products are formed, plus light and an explosive sound are released!
Watch this video that shows synthesis of water
electrolysisofwaterinstareel.MP4*magnesium and oxygen -------> magnesium oxide
magnesium (2Mg) and oxygen (O2) forms magnesium oxide (2MgO).
We know a chemical reaction has occurred as new products are formed,
plus a colour change, and a gas and heat are released!
*We lit magnesium in air in the lab! Remember the bright, white sparks as the magnesium burnt and changed to a white magnesium oxide?
2. Decomposition Reaction:
One substance breaks down into two or more substances.
BREAKING!
WHAT IS HAPPENING ?
a compound breaks into parts
EXAMPLES...
water -----> hydrogen and oxygen
water (2H2O) decomposes to hydrogen (H2) and oxygen (O2)
when an electric current passes through it (electrolysis)
We know a chemical reaction has occurred as new products are formed.
watch this short and sweet video
-it shows a decomposition reaction.
3. Single Replacement reaction:
Reaction: When one element replaces another in a compound.
SINGLE SWAP!
WHAT IS HAPPENING?
a single element replaces an element in a compound
EXAMPLE...
hydrochloric acid and magnesium -----> magnesium chloride and hydrogen gas
hydrochloric acid (HCl) and magnesium (Mg) mix to become magnesium chloride (MgCl2) and hydrogen gas (H2)
We know a chemical reaction has occurred as new products are formed,
plus heat and an explosive noise is released!
Be sure to watch below,
this is an example of a single replacement reaction!
We can identify the gas being released as hydrogen due to the 'Pop Test. Watch here for more..
https://www.youtube.com/watch?v=0VonvhSzhR4
4. Double Replacement reaction:
The ion of one compound replaces the ion of another compound to form two new compounds!
DOUBLE SWAP!
WHAT IS HAPPENING?
An element from each of two compounds switch places, often giving a solid precipitate as a product
EXAMPLE..
lead nitrate and potassium iodide ----> potassium nitrate and lead iodide
(SOLID!)
We know a chemical reaction has occurred as new products are formed,
including a solid, insoluble precipitate (lead iodide)!
Study this diagram below to see what is happening
on an ion level.. they swap!
This can also be called a PRECIPITATE REACTION!
Watch below to see a very cool representation of what happens with a double replacement chemical reaction..
Lead nitrate and potassium iodide.mp4ANOTHER DOUBLE DISPLACEMENT REACTION
HAPPENS HERE BELOW 👇
SODIUM HYDROXIDE (aq) and COPPER SULFATE (aq)
---------> SODIUM SULFATE (aq) and COPPER HYDROXIDE (s)
The precipitate is the SOLID, this is denoted by the (s).
In this case, it is the copper hydroxide.
5. Combustion reaction:
Chemical reaction involving oxygen, usually generating heat and light
BUST!
WHAT IS HAPPENING?
An element from each of two compounds switch places
EXAMPLE..
FUEL + OXYGEN ------> CARBON DIOXIDE + WATER
A SUMMARY OF FOUR CHEMICAL REACTIONS!
Synthesis
(make)
Decomposition
(break)
Single Replacement
(one swaps)
Double Replacement
(two swap)
electrolysisINSTA.MP4Page updated
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