chemical changes Flashcards
what is the principle of chemical reaction
atoms cannot be never created nor destroyed in a chemical reaction (like how energy cannot be created nor destroyed)
what is the conservation of mass equations
- the left side of the equation ALWAYS EQUALS the right side of the equation
- chemical reactions involve the rearrangement of existing atoms, there is no loss or gain of atoms (left side = right side of equation)
what is the difference between physical and chemical reactions
Physical:
- no new substances are formed
- can usually be reversed
chemical:
- one or more new substances are formed
- not easily reversed
what is the word equation
reactant + reactant → product
what is the definition of matter
anything that has both mass and volume
what is the definition of composition
the types and amounts of simpler substances that make up a sample of matter
what is the definition of properties
the characteristics that give each substance a unique identity
what are physical properties
- properties a substance shows by itself without interacting with another substance
- color, melting point, boiling point, density
what are chemical properties
- properties a substance shows as it interacts with, or transforms into, other substances
- flammability, corrosiveness
what are the states of matter
- solid
- liquid
- gas
what are the properties of solid
- has a fixed shape and volume.
- may be hard or soft, rigid or flexible
- particles are closed together and organised
what are properties of liquid
- has a varying shape that conforms to the shape of the container(no fixed shape)
- has a fixed volume
- has an upper surface
- particles are close to each other but disorganised
what are indicators of a chemical change
- burning/fire
- bubbles/fizzes (effervescent)
- temperature change (without heating or cooling)
- explosion
- colour change
- odour change
what are indicators of a physical change
- phase changes (changes in state of matter)
- mixtures (usually)
what are properties of gas
- no fixed shape
- no fixed volume
- therefore does not have a surface.
- particles are far apart and disorganised
what are the 2 categories of chemical changes
- reactions in which two or more substances chemically combine to form one or more new substances (eg. carbon burns in the presence of oxygen)
- reactions in which a substance breaks down into two or more new substances
what is combustion
- object breaks down into any substance(s), (not fixed) → needs heat
- a substance is heated in the presence of oxygen, heat and light is given out e.g. fossil fuels burnt to create energy
what is thermal decomposition
the process of an object that breaks down into two or more simpler substances
what is oxidation
- does not need heat
- gain of oxygen (e.g. Ca (calcium) gained O (oxygen) and has been oxidised to form CaO)
acid + base =
what is neutralisation with a base
acid + base = salt + water (only)
how to find the name of an ion
the element name + ‘ide’ (e.g. chlorine ion = chloride)
what is the definition of electrolysis and electroplating
using electricity to move the atoms/ions in metal from one place to another
all acids are __ when dissolved in water
H⁺
what is the hazards of acids and alkalis
- some acids and alkalis may be toxic or corrosive
- warning symbols: acute toxicity, corrosives
what are some lab equipment that helps with identifying the alkalis and acids
- litmus paper → determines only if the substance is acidic or alkaline
- pH paper → gives a more precise reading (pH value) than litmus paper
what does pH stand for
pH: p = potential/power (of hydrogen), H = hydrogen ion
what are some common acids used in the lab + chemical formula
- hydrochloric acid - HCl
- sulfuric acid - H₂SO₄
- nitric acid - HNO₃
what is the name of the salt produced from hydrochloric acid (HCl)
(metal) chloride
what is the name of the salt produced from sulfuric acid (H₂SO₄)
metal sulfate
what is the name of the salt produced from nitric acid (HNO₃)
metal nitrate
what are common features in acids
- all acids are sour
- all acids contain hydrogen (therefore, the chemical formula always starts with H)
- Acids turn blue litmus paper red.
- Acids dissolve in water to form solutions which can conduct electricity.
lower pH = __ acids
stronger
what are bases
alkalis
(all alkalis are bases)
what are some common alkalis (+ chemical formula)
- sodium hydroxide - NaOH (e.g. toothpaste, soap)
- ammonium hydroxide - NH (e.g. cleaning product, fertiliser)
all alkalis are __ when dissolved in water
OH⁻
what pH level is neutral
7
higher pH = ___ alkali
stronger
what colour does litmus paper turn when it is put in acids
red
what colour does litmus paper turn when it is put in alkali
blue
what is the definition of universal indicators
a pH indicator made of a solution of several compounds that exhibit various smooth colour changes over a wide range pH values to indicate the acidity or alkalinity of solutions.
how to read pH scale
- strong acids → weak acids → neutrals → weak alkalis → strong alkalis
- red to light green = acid
- dark green to purple = alkali
what does pH paper tell us
- determines if the substance is acidic or alkaline and the numerical pH value
- therefore, gives a more precise reading (exact pH value) than litmus paper
what does litmus paper tell us
- determines only if the substance is acidic or alkaline
- blue litmus paper turns red in acids, red litmus paper turns blue in alkalis
what is the formulae to find ionic compounds
cross multiply
what is chemical equations
A chemical equation shows what happens in a chemical reaction
how is the chemical formulae of ionic compounds formed
- by balancing the charges on the positive and negative ions.
- all the positive charges must equal all the negative charges in an ionic compound.
what can chemical equations tell us
- which reactants and products are involved in the reaction
- the relative amounts of reactants and products
- the physical states of the reactants and products of the reaction.
what is a balanced chemical equation
must contain equal numbers of atoms of each element on both sides of the equation.
what is on the left side of a chemical equation
The reactant(s)
e.g. 2H₂(g) + O₂(g) → 2H₂O(l)
what is on the right side of a chemical reaction
The product(s)
e.g. 2H₂(g) + O₂(g) → 2H₂O(l)
what are the state symbols
(s) – solid
(g) – gas
(l) – liquid
(aq) – aqueous solution (dissolved in water)
how to make chemical equation balanced
- Write down the chemical formulae of the reactants and products to get the chemical equation.
- Check the number of atoms of each element in the formulae on both sides of the equation.
if the equation is not balanced: - Add the state symbols to indicate the physical state of each reactant and product.
how to meassure the pH of given substance
- Chemical compound called an indicator
- pH sensor attached to a data logger
- pH meter
application of pH scale
pH of Soil:
- Most plants grow best in neutral or slightly acidic soils.
- It is important to control the pH of soil because it will affect the growth and development of plants.
related to soil too
another application of pH scale
Controlling pH of Soil:
pH of soil may become unsuitable for plant growth due to:
* too much fertilisers added to the soil
* environmental pollution such as acid rain.
To treat acidity in soil, add:
* calcium oxide (quicklime)
* calcium hydroxide (slaked lime)
what is the general equation for acid and alkali
acid + alkali = salt + water
what is the general equation for acids + metal carbonate
acids + metal carbonate = salt + water + carbon dioxide
what is the chemical formula for water
H₂0
what is the general equation for acids + metal
acids + metal = salt + hydrogen
what is the chemical formula for hydrogen gas
H₂
what is the chemical formula for carbon dioxide
CO₂
what is the chemical formula for oxygen gas
0₂
what is the chemical formula for chlorine gas
Cl₂
what do you do when you want to find out whether hydrogen gas is present
- carry out the experiment(e.g. acid +metal)
- place a lighted splint near the solution
- if the lighted splint extinguishes with a pop sound, hydrogen is present
what do you do when you want to find out whether carbon dioxide is present
- carry out the experiment(e.g. acid+ carbonate)
- bubble the gas into limewater/calcium hydroxide)
- if white precipitate forms in limewater, carbon dioxide is present (effervesence)
what is the chemical formula for sulfate ION
SO₄²⁻
what is the chemical formula for ammonium ION
NH₄⁺
what is the chemical formula for hydorxide ION
OH⁻
what is the chemical formula for nitrate ION
NO₃⁻
what is the chemical formula for carbonate ION
CO₃²⁻
what is the chemical formula for chloride ION
Cl⁻
what is the chemical formula for sodium ION
Na⁺
what is the chemical formula for potassium ION
K⁺
what is the chemical formula for magnesium ION
Ma²⁺
what is the chemical formula for calcium ION
Ca²⁺
what is the chemical formula for copper(II) ION
Cu²⁺
what is the chemical formula for iron(II) ION
Fe²⁺
what is the chemical formula for iron(III) ION
Fe³⁺
what is the chemical formula for silver ION
Ag⁺
what is the chemical formula for zinc ION
Zn²⁺
what is the chemical formula for aluminum ION
Al³⁺
what is the chemicla formula for calcium and carbonate
CaCO₃
what is the chemical formula for calcium and nitric
Ca(NO₃)₂
what is the chemical formula for calcium and sulfric
CaSO₄
what is the chemical formual for calcium and chloride
CaCl₂
what is the chemical formula for magnesium and chloride
MgCl₂
what is the chemical formula for magnesium and sulfric
MgSO₃
what is the chemical formula for magnesium and carbonate
MgCO₃
what is the chemical formula fro magnesium and nitrate
Mg(NO₃)₂
what is the chemical formula for potassium and chloride
KCl
what is the chemical formula for potassium and sulfric
K₂SO₄
what is the chemical formula for potassium and carbonate
K₂CO₃
what is the chemical formula for potassium and nitrate
KNO₃
what is the chemical formula for sodium and chloride
NaCl
what is the chemical formula for sodium and sulfric
Na₂SO₄
what is the chemical formula for sodium and carbonate
Na₂CO₃
what is the chemical formula for sodium and nitrate
NaNO₃
what is the chemical formula for copper(II) and chloride
CuCl₂
what is the chemical formula for copper(II) and sulfric
CuSO₄
what is the chemical formula for copper(II) and carbonate
CuCO₃
what is the chemical formula fro copper(II) and nitrate
Cu(NO₃)₂
what is the chemical formula for zinc and chloride
ZnCl₂
what is the chemical formula for zinc and nitrate
Zn(NO₃)₂
what is the chemical formula for zinc and sulfric
ZnSO₄
what is the chemical formula for zinc and carbonate
ZnCO₃
what is the chemical formula for aluminium and sulfric
Al₂(SO₄)₃
what is the chemical formula for aluminium and nitrate
Al(NO₃)₃
what is the chemical formula for aluminium and carbonate
Al₂(CO₃)₃
what is the chemical formula for aluminium and chloride
AlCl₃
what are some examples of acidic substance at pH level 1
battery acid
what is an examples of a substance at pH level 2
lemon juice
what is an example of a substance at pH level 3
vinegar
what is an example of a substance at pH level 4
tomato juice
what is an example of a substance at pH level 5
coffee
what is an example of a substance at pH level 6
milk
what is an example of a substance at pH level 7
pure water
what is an example of a substance at pH level 8
sea water/eggs
what is an example of a suubstance at pH level 9
baking soda
what is an example of a substance at pH level 10
milk of magnesia
what is an example of a substance at pH level 11
ammonia solution
what is an example of a substance at pH level 12
soapy water
what is an example of a substance at pH level 13
bleach
what is an example of a substance at pH level 14
liquid drain cleaner
when do you add bracket
when an ion is made up of multiple atoms (poly atomic)
take it as one whole thing
