term 2 Flashcards
What is a compound?
when two or more elements join together by chemical bonds. These compounds are always formed within a fixed ratio.
How is a compound different from an element?
An element is a substance made of one type of atom with the same number of protons. A compound is a substance made of two or more elements in definite proportions that are joined by chemical bonds. An element cannot be broken down into smaller substances, whereas a compound can be broken down by chemical processes
How is a mixture of elements different from a compound?
Compounds contain different elements in a fixed ratio arranged in a defined manner through chemical bonds. They contain only one type of molecule. Elements that compose the compound are chemically combined. Mixtures contain different elements and compounds but the ratio is not fixed nor are they combined via chemical bonds.
What does the position of an element on the periodic table tell us about it’s properties?
we can know if it’s metal/non-metal/semi-metal, it’s energy levels even it’s properties/characters
Where do we find metals on the PT?
Metals are found on the left hand side of the table.
Where do we find non-metals on PT?
Non-metals are found on the far right hand side of the table.
Where do we find semi-metals on PT?
Semi-metals are found in the region between metals and non-metals.
What does the formula of a compound tell us about it?
When you have a look at the formula and see the numbers, also called subscripts, that will tell you how many atoms of that specific element are in one molecule of that compound.
What do we call the vertical columns in PT?
period
What do we call horizontal columns in PT?
group
What do the elements that are in the same group in PT have in common ?
they have similar physical properties or chemical characteristics that they share, because of the outer electron shell of the atom that has the same charge.
What additional information about an element can we find on PT?
In addition to listing the atomic number for each element, the periodic table also displays the element’s relative atomic mass, the weighted average for its naturally occurring isotopes on earth.
What is a chemical reaction?
the process in which atoms in molecules would rearrange themselves to form new molecules.
How can I represent what happens in a chemical reaction?
using a chemical formula
What do numbers mean in a chemical reaction?
When you have a look at the chemical reaction/formula and see the numbers, also called subscripts, that will tell you how many atoms of that specific element are in one molecule of that compound.
How can we tell if a reaction is balanced?
if all there are the same number of atoms of the same kinds on elements before and after a chemical reaction
What does it mean to balance a chemical equation?
when the number and types of atoms on the left and the right are the same.
What’s t he difference between word/picture/chemical equations?
A picture equation is a visual representation of a chemical reaction that uses pictures or symbols to represent the reactants and products involved in the reaction. A word equation represents a chemical reaction using the names of the substances involved. Chemical equations are used to represent chemical reactions using chemical symbols and formulae.
What do different symbols in in a chemical reaction mean?
What happens when a metal reacts with oxygen?
metal oxide also rust happens but just say metal oxides in the exam
What is the product (of metal+oxygen) called?
metal oxide
A way to show general reaction btwn a metal and oxygen?
What is rust?
rust is a product of iron and oxygen
How does rust form?
rust is a product of iron and oxygen
What occurs whem non-metal and oxygen react?
What is the product of (non-metal+oxygen)?
Do all non-metals form dioxides with oxygen?
How should we write equations for the reaction of carbon with oxygen?
How should we write equations for the reaction of sulfur with oxygen?
What is the reaction between an acid and a base called?
What happens to the pH when an acid and a base are mixed?
Are there general equations to explain these reactions?
What is the general equation for the reaction between a metal and an acid?
How do we write the word equation and the balanced chemical equation?
How can we test for the presence of hydrogen gas?
define ions
An atom that bears one or more negative or positive electrical charges.
define Ionic bonds
This refers to the electrostatic force of attraction between two oppositely charged ions.
define subscript
It is the number of atoms of a specific element contained in a compound.
define convention
The way in which certain tasks are usually done and overall accepted.
What is element?
It is the purest form of a substance that cannot be broken down into smaller parts or sub-parts.
define atom
an atom is the smallest part or amounts of elements
what are isotopes
Isotopes are atoms that have the same number of protons and electrons, but a different number of neutrons.
list the differences between elements and atoms.
ATOMS=(Smallest part of an element.)(Made of electrons, protons, and neutrons.)(Contain only one nucleus with different
numbers of electrons, protons, and neutrons.)(Atoms combine to form molecules.)
ELEMENTS=(Cannot be simplified as atoms cannot be simplified
and an element is just a type of atom.)(Made from one type of atom.)(Atoms have the same number of protons.)(Elements combine to form compounds.)
define a proton
Positively charged atomic particle found inside the nucleus of an atom.
define an electron
Negatively charged atomic particle that move around the nucleus of an atom.
define a neutron
It is found in the nucleus and is neutral in electric charge. It has about the same mass and diameter as a proton. Neutrons are found in all atoms except for most atoms of hydrogen.
How do compounds form?
Atoms in different compounds would separate and break bonds with each other and reconnect to other compounds through new chemical bonds.
what would be the ration for two hydrogens and one oxygen
two hydrogens to every one oxygen 2:1.
list all the ways compounds are formed
Some compounds form clusters called molecules while other compounds arrange themselves in regular patterns called a crystal lattice.
define decomposition
when substances break down
define synthesis
when substances are joining together
what are reactants
(the materials we start with)
what are products
(new materials formed)
what is activation energy
The application of energy is needed for these stable bonds to break. This energy is usually in the form of heat, pressure or electricity.
what is Submicroscopic representation
using imagination to represent atoms/elements that we can not see it with our eyes
what is Macroscopic representation
This is a representation that we can observe using our senses.
what is symbolic representation
A symbolic representation is the use of chemical symbols to represent a compound.
list Chemical properties
Reactivity → The tendency of matter to combine with other substances.
Flammability → The tendency of matter to burn.
Toxicity → The extent to which chemical elements can harm an organism.
Acidity → The ability to react with an acid.
list Physical properties
Density → How compact is the substance?
Colour → Is it colourless or does it have a colour and if so, which colour?
Mass → What is the weight of the substance?
Volume → The amount of space that a substance takes up.
Length → Can you measure the length of a molecule?
Odour → Does the substance smell like anything? Is it a well-known smell?
Temperature → Does the substance have a different temperature? Is it easy or difficult to heat or cool?
Hardness → Can the substance be broken?
Chemical reaction of photosynthesis
C6H12O6 + 6O2
Law of conservation of matter
Matter is never created or destroyed, it simply cycles through the world.
define matter
We define matter as anything that has both mass and volume.
define mass
The measure of the amount of matter in a substance/object.
define volume
The measure of the amount of space that a substance/object takes up.
what are coeffecients
The numbers in front of the formulae in chemical equations are called coefficients. Coefficients represent the number of individual molecules of an element that are present in the chemical reaction.
Why do you think it is important that equations need to be balanced?
Equations must be balanced to accurately reflect the law of conservation of matter.
define Conserved
Maintain at a constant total.
what is balance
something that is evenly distributed
balancing equation means
it means atoms before and after the chemical reaction will be the same
what is it that you can and cannot change when balancing an equation
you can’t change the subscripts you can change the coefficients
what’s the largest group of elements in the pt
metals
what’s the smallest group of elements in the pt
semi-metals
melting point
the temperature at which an object starts to melt
odourless
something with no recognizable smell
electrical insulator
preventing electricity from going through the material
thermal conductivity
can spread the heat evenly throughout specific types of material
iron +oxygen=
iron oxide
balanced rust equation
2Fe²O³
ways to prevent rust formation
- painting the steel/iron steel 2.using other metals(that are rust resistant e.g chronium) as a barrier
when was magnesium discovered and who discovered it
Magnesium was first discovered in 1755 by Joseph Black
what type of magnesium is used in meds
Magnesium hydroxide, it regulates the body’s muscle and nerve functioning. It also regulates blood sugar levels and blood pressure as well as assists in making protein, bones and DNA!
what is combustion
This refers to the chemical reaction that takes place between a substance and oxygen, causing it to be lit on fire and produce a bright flame.
pros of magnesium
Magnesium combines really well with aluminium. It improves the overall properties of the metal and is used in aeroplanes and the construction of cars
cons of magnesium
magnesium combusts easily and brightly
magnesium in it’s ,most basic state
it has a white silvery appearance
is magnesium found in it’s raw form
no Magnesium is not found naturally in its raw form.
how was magnesium discovered
Joseph Black heated various rock forms, limestone and magnesite, and discovered magnesium oxide and calcium oxide.
balanced chemical equation for magnesium oxide
2Mg + O2 → 2MgO
word equation for magnesium oxide is
Magnesium + oxygen → Magnesium oxide
word equation for respiration
glucose+oxygen~> carbon dioxide+water
chemical equation for repiration
C6H12O6+6O2~>6CO2+6H2O
What do you think would happen if the air we breathe was 100% oxygen?
While oxygen keeps us alive, too much oxygen is actually toxic to the human body! Hyperoxemia or oxygen poisoning can cause coughing, breathing difficulties and even death.
how much oxygen is in the air?
The air we breathe only contains 21% oxygen.
non-metals properties
Non-metals are generally poor conductors of heat and electricity.
Non-metals are naturally found as solids, liquids and gases.
Noble gases are non-metal elements that do not bond with other atoms.
Non-metals generally have a lower melting and boiling point than metals.
The solid form of non-metals is usually brittle, which means that it breaks easily.
Carbon + oxygen
carbon dioxide
Sulphur + oxygen
sulphur dioxide
Hydrogen + oxygen
dihydrogen oxide (water)
Chlorine + oxygen
chlorine dioxide
Nitrogen + oxygen
nitrogen oxide
The general equation for Non-metals reacting with oxygen
Non-metal + Oxygen → Non-metal oxide
Preventing a global disaster
To prevent further global warming and climate change, we urgently need to move away from using fossil fuels as our main energy sources and rather focus on renewable, carbon-neutral energy sources.
what happens as global temperatures rise
As global temperatures rise, sea ice and glaciers begin to melt, releasing vast quantities of water into our oceans. This causes the sea levels to rise, flooding coastal areas.
Weather patterns are also controlled by temperature and as the planet’s temperatures rise, the climate changes as well. Some areas will experience increased flooding, while others experience devastating droughts. Storms and other natural disasters also increase in intensity, becoming more and more dangerous as the climate changes.
chemical formula for carbon dioxide
C + O2 → CO2
Combustion produces what
light and heat
we mainly use what when generating heat and electricity.
Wood, coal, oil and natural gas are the fuels that we mainly use when generating heat and electricity.
Fossil fuels
These are fuels that have been formed over millions of years from the remains of living organisms. These fuels contain vast amounts of carbon.
Fossil fuels include
coal, oil and natural gas
carbon + oxygen fully explained
carbon is combustible and reacts with atmospheric oxygen to release carbon dioxide. This reaction also produces heat and light but also, pollution.
why do we use fossil fuels for electricity
because it was cheap and readily available or easy to mine.
The combustion of fossil fuels is problematic for a number of reasons:
1.Fossil fuels are classified as finite resources. This means that the Earth only contains a set amount of these substances and these will eventually be used up. This is why there is a drive across the world to find renewable alternatives.
2.During the combustion of carbon, carbon dioxide gas is formed. This is released back into the atmosphere. The release of this gas is known as carbon emissions and these are worse for countries who have manufacturing industries. Have a look at the graph below for a comparison of emissions among the regions of the world since the Industrial Revolution.
what kind of gas is a greenhouse gas
Carbon dioxide is a greenhouse gas.
greenhouse gas
gas that is able to trap heat in the Earth’s atmosphere.
global warming explained
This trapped heat causes the atmospheric temperature to increase. The more carbon dioxide in the atmosphere, the more heat will be trapped and the hotter the Earth will become.
Other planets with high carbon emissions
1.Venus has the highest amount of carbon in its atmosphere at 96%.
2.Mars also has a high carbon index with 95% while 3.Pluto has 8% carbon in its atmosphere. ( the Earth only has 0.04% carbon dioxide in the atmosphere.)
scientific name for rust
iron oxide
what is the fifth most common element by mass on earth
sulphur
S + O2
SO2
Do you remember what the atomic number tells us about an element?
the atomic number tells us how many protons are located in the nucleus of an atom of this element.
what makes compound special
Compounds have a specific chemical formula and the atoms that compose them are found in fixed ratios.
Properties of acids
Acids taste sour
They feel rough between your fingers
They can be corrosive
They can cause bases to lose their basic character
They will turn blue litmus paper red.
Properties of bases.
Bases taste bitter
They feel slippery between your fingers
They can be corrosive
They can cause acids to lose their acidic character
Turn red litmus paper blue
Acid
Any hydrogen containing substance that is capable of donating a proton to another substance.
Base
A base is a molecule or ion able to accept a hydrogen proton from an acid.
what happens when you add a base to an acid
the acid will become less acidic
what happens when you add an acid to a base
the base will become less basic.
what body part has a lot of acid
the stomach
what type of acid does the stomach contain
one of the strongest acids? Gastric acid has a pH of 1.5!
why does the stomach need such strong acid
Your stomach needs this acidity to be able to maintain digestive health. It acts as the first line of defence against harmful bacteria and viruses. This environment of a pH between 1.5 and 2.5 is responsible for the activation of enzymes that help break down protein into smaller protein fragments. This is the first step in digesting food.
. Since our stomach is already an acidic environment, what happens if we take in too much acid?
Abdominal discomfort, especially on an empty stomach
Nausea
Heartburn
Unexplained weight-loss due to rapid digestion
Bloating due to acid build-up
Acid reflux
Acid reflux is a disease where stomach acid pushes back up into your esophagus and irritates the lining.
How to combat acid reflux
To prevent reflux from happening you need to limit the acid intake and carefully watch the acidity levels of the food you eat by using a universal chemical indicator.
You should also avoid lying down straight after a meal.
Sometimes when you have sudden reflux it could help to get antacids
Antacids
Antacids contain an ingredient called Milk of Magnesia and neutralises the amount of acid in your stomach.
Common acids used in industries
Sulfuric acid
Nitric acid
Hydrochloric acid
Household acids and bases
Dishwashing liquid pH 5.5
Lubricating oil spray pH 7.6
Window cleaner pH 8
Industrial chemicals
Potassium hydroxide
Sodium hydroxide
Calcium hydroxide
sodium hydroxide
It is a highly corrosive white crystalline solid that will absorb any kind of moisture instantly. (used in different soaps, paper production and even explosive materials)
calcium hydroxide
Calcium hydroxide is a colourless crystal or white powder. This chemical is used in sewage treatment, paper production, construction and even food processing.
Sulfuric acid
chemical is highly corrosive and destructive to the skin, eyes and teeth. can lead to death-used in producing fertilizers, dyes, explosives and drugs. -used in metal industries due to the ability to remove oxidation from steel and other metals.
Nitric acid
it is a colourless liquid, but over time turns a yellow colour due to decomposition of oxides in nitrogen and water. Nitric acid is used in fertilisers and also explosive materials such as trinitrotoluene (TNT).
Hydrochloric acid
a colourless chemical, but it comes with a pungent smell and is considered a very strong acid. This chemical is mostly used in photographic, rubber and textile industries. It is used as a bleaching agent to remove tough stains such as rust from metals.
Potassium hydroxide
a white or slightly yellow, flakey/ lumpy solid that is usually in a water solution. This substance is odourless. This versatile base is used in soap, as electrolytes in alkaline batteries and in electroplating, paint and even various varnish removers. Some drain cleaners contain up to 35% of potassium hydroxide. This chemical reacts violently with various acids and should be handled very carefully. Any skin or eye contact with potassium hydroxide will need urgent emergency care.
Various chemical indicators
LITMUS PAPER
CABBAGE WATER
UNIVERSAL INDICATOR
PH METER
Other chemical indicators
Red onion water
Turmeric water
Phenolphthalein
Bromothymol blue
