chap 11 chemical changes Flashcards
what are properties of physical changes
- no new substances formed
- changes are usually reversible
- properties of the products are thee same as the reactants
what are properties of chemical changes
- one or more new substances formed
- changes are usually not reversible
- properties of the products are different from the reactants
- energy ( heat or light ) is taken in or given out
Atoms are….
neither created nor destroyed
Mass is ___ during a chemical reaction
conserved
what is combustion and its equation
it is when a substance is heated in oxygen
eg: C + O2 = CO2
what is thermal decomposition and its equation?
It is when a substance breaks down into two or more simpler substances upon heating
Calcium carbonate -> (heat) calcium oxide + carbon dioxide
what is oxidation and its equation?
It is when a substance gains oxygen
eg: rusting ( iron reacts with oxygen and water ), respiration
Glucose + oxygen -> carbon dioxide + water
what is neutralisation and equation
It is when an acid reacts with an alkali
Acid + alkali -> salt + water
what are the physical properties of acid?
- sour taste
- corrosive
-
turns blue litmus paper into red
( bc red is acidic )
what are the physical properties of alkali?
- bitter taste
- feels soapy
- corrosive
- turns red litmus paper into blue
( blue is alkaline )
what are the chemical properties of acid?
Reacts with
- metals,
- alkalis
- carbonate
what are the chemical properties of alkalis?
Reacts with
- acids
**name of acids has __ at the back
acid
eg: sulfuric acid
**examples of alkali has __ at the back
hydroxide
How do you test for
1) acid
2) alkali
3) what this process is called
4) equation
1) Check whether substance turns blue litmus paper into red
2) Check whether substance turns red litmus paper into blue
3) neutralisation
4) acid + alkali →salt + water
**1) how do you test for hydrogen gas?
2) equation
1) insert a lighted splint into the test tube( containing the metal and acid ) , the lighted splint extinguishes with a “pop” sound.
2) acid + metal →salt + hydrogen gas
*What types of metal do not react with acids?
copper, silver and gold ( think of the medals thing )
why is the process called neutralisation?
It is because when acid and alkali is added together, the salt solution form is neutral. ( pH = 7 )
**1) how do you test for carbon dioxide?
1.5) process of precipitate being formed.
2) equation
1) bubble the gas produced by blowing into the straw into limewater, white precipitate is formed if the gas is CO2.
1.5) which is a process called effervescence
2) acid + carbonate → salt + water + carbon dioxide
pH scale, how do we define what is acidic and akaline?
pH <7 are acidic, the lower the pH the more acidic
pH 7> are alkaline, the higher the pH the more alkaline
pH 7 are neutral. They are neither acidic nor alkaline.
Chemical changes can occur as a result of…. ( 5 )
- Mixing
- Heating
- Exposure to light
- Interacting with oxygen
- Using an electric current.
What are the chemical changes for
1) mixing
2) heating
3) exposure to light
4) interaction with oxygen
5) using an electric current
1) eg acid+alkali
2) combustion, thermal decomposition
3) photosynthesis
4) oxidation, rusting, respiration
5) electroplating
What happens to atoms during a chemical reaction?
The atoms rearrange themselves to chemically combine and form new substances.
*How do you prevent decay/decomposition?
Vacuum packaging can remove air (oxygen) from the package, limiting the growth of bacteria and other microorganisms.
