CW3 Chemical Reactions and CW4 Rates of Reaction

Question 1

Define catalyst
Relationship between surface area and rate of reaction

Answer 1

Catalyst: chemicals which increases the rate of a reaction without being used up itself.
Higher surface area increases exposed particle’s chance to react consequently increasing frequency of particle collision therefore increasing rate of reaction

Question 2

Relationship between concentration of reactants and rate of reaction
Relationship between temperature and rate of reaction

Answer 2

An increase in the concentration of reactants increases the rate of reaction as they are a greater number of particles to react consequently increasing the frequency of collisions.
An increase in temperature increases the kinetic energy of particles consequently increasing the frequency of particle collisions and a greater proportion of collisions will possess the energy to react.

Question 3

Relationship between pressure of reaction in gases and rate of reaction
Relationship between catalyst and rate of reaction

Answer 3

Increasing the pressure of a reaction involving gases forces the gas particles closer. This will increase the frequency of particle collisions, and therefore increase the rate of reaction.
A catalyst provides an alternative route for the reaction with a lower activation energy. This means that particle collisions need less energy in order for a reaction to occur, increasing the rate of reaction.They make it easier for reactant molecules to collide and form products.

Question 4

Difference between
Reliability
Accuracy
Validity

Answer 4

The extent to which the findings of repeated experiments, conducted under identical or similar conditions, agree with each other.
The extent to which a measured value agrees with its true value
The extent to which an experiment addresses the question under investigation.

Question 5

Define temperature
Define chemical energy

Answer 5

A measurement of the warmth or coldness of an object
Energy stored in the chemical bonds between atoms in a molecule. It can be released when chemicals break apart (eg burning) or absorbed when they are joined (eg photosynthesis)

Question 6

Describe the process of an exothermic reaction

Answer 6

Reactions that release energy are called exothermic reactions. In an exothermic reaction, the products have less stored energy than the reactants at the start of the reaction. The thermal energy produced in an exothermic reaction comes from the chemical energy stored in the bonds between the atoms of the reactants. When these bonds break, the energy is released and goes into the surroundings, usually causing the temperature to rise.

Question 7

Describe the process of an endothermic reaction

Answer 7

Chemical reactions that absorb energy are called endothermic. In an endothermic reaction, energy is taken from the surroundings and the products have more energy than the reactants. Since energy is being removed from the surroundings, endothermic reactions will often cause the temperature of the surroundings to drop.

Question 8

Application of exothermic reactions

Answer 8

No heat is not needed to burn coal , rather burning coal produces heat. But for the burning reaction to start it needs a small boost of energy(activation energy) to start; once started it sustains itself and continues to produce heat up to the end. That is why it is called exothermic

Question 9

How is a chemical bond formed and broken

Answer 9

To form the chemical bond, energy from reaction is released to the surrounding resulting increase of temperature of surrounding. To break the chemical bond, energy from surrounding is absorbed resulting decrease of temperature of surrounding.

Question 10

Application of endothermic reactions

Answer 10

An application of endothermic reactions include cold packs. Cold packs reduce swellings and numb pain caused by injuries. They usually contain ammonium nitrate, which undergoes an endothermic reaction when the inner bag is broken. This allows the salt to dissolve in water,absorbing the thermal energy of the water in the process. This cools the water and makes the bag feel cold.

Question 11

Define combustion
Combustion word equation
Difference between incomplete and complete combustion

Answer 11

An exothermic reaction in which a fuel reacts with oxygen to release energy detected as heat and light
Combustion(burning) always have oxygen as a reactant and water and carbon dioxide as products.
fuel + oxygen → carbon dioxide + water
Complete combustion of a hydrocarbon (organic compound consisting entirely of hydrogen and carbon) always produces CO2 and H2O.
Incomplete combustion of a hydrocarbon will produce CO and possibly C (black carbon soot) as well.

Question 12

Define exothermic
Equation for photosynthesis
Equation for respiration

Answer 12

Reactions in which heat energy is released from the reaction to the surroundings
Sunlight + carbon dioxide + water → glucose + oxygen
Glucose + oxygen → carbon dioxide + water + energy

Question 13

Define respiration

Answer 13

An exothermic reaction which takes place in living cells in which energy is released from a reaction between glucose and oxygen and does not require an external source of heat

Question 14

Define digestion
Types of digestion

Answer 14

The process in which nutrients and energy are extracted from the food we eat so that it can be in a form that can be absorbed by the body’s cells.
The two types are:
Mechanical digestion which occurs in the mouth when food is physically broken down or mashed into smaller pieces (without enzymes).
Chemical digestion, which occurs at various stages along the alimentary canal, when special chemicals called enzymes chemically breakdown food.

Question 15

Where are bile salts made?
Where do bile salts works?
Substrate (what bile salts acts on)
Products

Answer 15

Liver
Small intestine
Fat
Fat products

Question 16

Define spontaneous combustion
Define rapid combustion
Define explosion

Answer 16

The combustion in which substances starts burning suddenly even without being heated e.g. sodium and phosphorus burn spontaneously in air, even when no external heat is provided to them.

The combustion in which substances burn rapidly to produce heat and light is called rapid combustion. In rapid combustion,external heat must be supplied so that the substances can burn. E.g. oil lamp, burns rapidly to produce heat and light when they come in contact
with fire.

A combustion reaction that occurs suddenly when a material is heated, liberating a large amount of gas and producing heat, light and sound

Question 17

Define atom
Define element
Define molecule
Define compound

Answer 17

The smallest particle of an element that has all of the chemical properties of that element.
An element is a substance that is made of only one type of atom; it cannot be decomposed. It is represented by a single shape or two of the same shape joined together.
Two or more atoms that are joined by a chemical bond.
A chemical substance formed from two or more elements, with a fixed ratio determining the
composition

Question 18

Define enzyme

Answer 18

A substance produced by a living organism which acts as a catalyst to bring about a specific biochemical reaction

Question 19

Define indicator
Define acidic
Define base
Define alkaline

Answer 19

A chemical that changes colour when exposed to certain conditions and is therefore useful for chemical tests.
A substance which contains hydrogen and dissolves in water to produce one or more hydrogen ions
A substance that has a pH greater than 7 and has hydroxide or carbonate as part of their name.
A base that is soluble in water.

Question 20

Define chemical reaction

Answer 20

A process involving one, two or more substances (called reactants), characterised by a chemical change and yielding one or more product(s) which are different from the reactants

Question 21

What do all chemical reactions involve?

Answer 21

All chemical reactions involve bond breaking and bond forming. Energy is needed to break bonds and released when bonds are formed.Chemical reactions are accompanied by a change in
energy, mainly in the form of heat.

Question 22

What must occur for a chemical reaction to occur (collision theory)

Answer 22

According to The Collision theory, for a chemical reaction to happen, the following needs to happen:
that reactant particles must collide with each other,
that particles must have enough energy for them to react and
that they must collide with the correct orientation.

Question 23

Example of enzyme application

Answer 23

Some washing powders have enzymes in them, to speed up the breakdown of dirt and stains. Chemicals (fats, stains) that might have stayed for months are broken down in minutes. It also saves energy, as you don’t need to use hot water to clean.

Question 24

Shape of atom
What determines element and properties of element

Answer 24

Every atom is made up of protons and neutrons in the nucleus, which are surrounded by layers of orbiting electrons in electron shells. The number and arrangement of the subatomic particles determine the element and the properties of that element.

Question 25

What makes an element’s particles?

Answer 25

An element’s particles can be either single atoms, or molecules containing identical atoms (e.g. oxygen molecules, O2 ).

Question 26

Pure vs Impure Substances

Answer 26

A pure substance contains only one type of particle. They can not be separated into simpler substances using physical techniques. Elements and compounds are examples of pure substances.

Mixtures are impure substances – they have two or more different types of particles, which can be separated using physical separation techniques (e.g. filtration etc.) as they are not chemically bonded together. Impure materials may be mixtures of elements, mixtures of compounds, or mixtures of elements and compounds.

Compounds are made of only one kind of molecule.

Question 27

Position of metals, non-metals, metalloids

Answer 27

The metals are to the left of the line (except for hydrogen, which is a nonmetal), the nonmetals are to the right of the line, and the elements immediately adjacent to the line are the metalloids.

Question 28

Properties of metal

Answer 28

• A metal is an element that is found on the left-hand side of the staircase line on the Periodic table.
•Are good conductors of heat
and electricity,
•Are malleable (can be bent into different shapes)
•Are ductile (can be made into wire)
•Are lustrous (can be polished to produce a high shine)
•Have high melting points.
•All metals, except mercury, are solids at room temperature and pressure

Question 29

Properties of non-metals

Answer 29

•A non-metal is an element that is found on the right-hand side of the staircase line on the Periodic table.
•Are usually non or poor conductors of heat and electricity,
•Are brittle (shatter when they are hit). They cannot be bent into shape.
•Are non-ductile
•Are dull when they are in their solid form
•Have low melting points..
•Many of the non-metals are gases at room temperature.

Question 30

Arrangement of periodic table of elements

Answer 30

Elements are classified into families according to their
different chemical properties and arranged in the Periodic
Table they so that:
families of elements with similar chemical properties
are in vertical columns called groups (numbered I to vIII)
elements are arranged in order of increasing atomic
number – small, light atoms are towards the top of the table,
larger, heavier atoms are towards the bottom
horizontal rows are called periods (numbered 1 to 7).
The periodic table is called “periodic” because it has patterns that re- occur in a regular pattern.

Question 31

Groups in the periodic table

Answer 31

The periodic table contains 8 groups (or families) of elements, four of which have been given special names.
Group 1 elements (Li, Na, K) are called the alkali metals. They are all metals and solids at room
temperature. They all have one electron in the outer electron orbit and form ions with a charge of
+1. They react with water.
• Group 2 elements (Be, Mg, Ca) are called the alkaline earth metals. They are all metals and are solids
at room temperature. They all have two electrons in the outer electron orbit and form ions with a
charge of +2. They react with acid.
• Group 7 elements (F, Cl, Br, I) are called the halogens. They are all metals and are solids, liquids and
gases at room temperature. They form ions with a charge of –1.
• Group 8 elements (He, Ne, Ar) are called the inert gases or noble gases. They are all non-metals and
are gases at room temperature. They have a full outer electron orbit and so do not react with other elements.

Question 32

Characteristics of acids

Answer 32

Acids contain the element hydrogen in combination with other non metal elements,(HCl,H2SO4,HNO3).
Acids produce hydrogen ions (H+) when dissolved in solution.
Acids have a pH below 7
Acids have a sour taste (do not try this).
Acids turn blue litmus red.
Acids conduct electricity in aqueous (water) solution.

Question 33

Characteristics of basics

Answer 33

Bases produce hydroxide ions (OH– ) when dissolved in solution.
Bases have a pH above 7.
Bases taste bitter(do not try this).
Bases have a soapy feel (do not touch chemicals).
Bases turn red litmus blue.
Bases that dissolve in water are called alkalis.

Question 34

Difference between alkali and a base

Answer 34

Alkalis are substances that react with acids which are soluble in water while a base is a substance reacts with acids including metal oxides, hydroxide and carbonates

Question 35

Chemical formulas for hydrochloric acid, sulfuric acid, sodium hydroxide, ammonia, sodium chloride

Answer 35

HCl,
H₂SO₄
NaOH
NH3
NaCl

Question 36

Main types of carbonates (CO3)
Carbonate Equation
How to test for gas produced?

Answer 36

There are two main types of Carbonates:
Metal carbonates - these are made up of a metal and a carbonate ion - Eg: Calcium carbonate CaCO3 - Sodium Carbonate NaCO3
OR
Metal Hydrogen Carbonates - there are made up of a metal and a hydrogen carbonate ion eg: Sodium Hydrogen Carbonate NaHCO3 (commonly known as Baking Soda)
acid + carbonate →salt + water + carbon dioxide
Test for CO2 Gas: To test for carbon dioxide use Limewater (a solution of calcium hydroxide. So if we bubble carbon dioxide through the solution it reacts with calcium hydroxide solution to produce a white precipitate of calcium carbonate. We will observe that the limewater will turn milky or cloudy white).

Question 37

Define ammonia
Define pH
Define neutralisation

Answer 37

colourless, pungent gas composed of nitrogen and hydrogen
a measure that describes the relative acidity or alkalinity of a solution.
when an acid and a base react to form water and a salt and involves the combination of H+ ions and OH- ions to generate water.

Question 38

Types of indicators

Answer 38

Litmus, is made from plants called lichens. It is not very precise and only tells us whether a solution is acidic or basic.It is red in acidic solutions (below pH 7) and blue in alkaline solutions (above pH7).
A Universal indicator contains a number of indicators that turn different colours depending on the pH of the solution and hence is more precise as it gives us a good estimation of the pH of a solution.

Question 39

Signs of chemical reactions

Answer 39

the formation of a new substance (ALWAYS)
a change in temperature: heat is released or absorbed during the reaction.
a change in colour, the products are a different colour than the reactants.
production of a solid: a solid settles out of a liquid solution. The solid is called a precipitate (a change from solution to suspension).
the formation of a gas: bubbles are released during the reaction

Question 40

Acid + Metal equation

Answer 40

Magnesium reacts with hydrochloric acid to produce magnesium chloride and hydrogen gas. This can be summarised as:
Hydrochloric acid + Magnesium → magnesium chloride + hydrogen gas
Metal + acid → salt + hydrogen
To test for hydrogen use pop test (bring a lit match to the mouth of the test tube containing the metal + acid, and if it makes a pop sound it contains hydrogen)

Question 41

Neutralisation reaction

Answer 41

acid + base → salt + water
hydrochloric acid + sodium hydroxide → sodium chloride + water
Examples
Bee stings contain acid and so they are treated with bicarbonate of soda because it contains a base
that neutralises the acid.
Different acids will produce different salts in neutralisation reactions. For example, sulfuric acid will produce salts called sulfates. When hydrochloric acid reacts with sodium hydroxide, the salt sodium chloride (common table salt) and water are produced.

Question 42

Corrosion reaction
Acid + metal oxide reaction
Combination reaction
Decomposition reaction

Answer 42

Metal + oxygen → metal oxide
Acid + metal oxide → salt + water
Sulfuric acid + copper oxide → copper sulfate +water
Combination= x + y → xy
Decomposition= xy → x + y

Question 43

Define precipitate reactions

Answer 43

In a precipitation reaction, two solutions are mixed together to produce an insoluble solid called a precipitate
Soluble + Soluble → Solid Substance + Soluble
substance substance (precipitate) substance
copper + sodium →copper + sodium
sulfate hydroxide hydroxide. sulfate
Copper hydroxide is insoluble in water and so it is the precipitate.

Question 44

Define corrosion and galvanising

Answer 44

A natural process in which a refined metal is converted to a more chemically stable form, such as oxide, hydroxide, or sulphide.
The process of applying zinc coating to a more noble metal to prevent corrosion

Question 45

Define sacrificial protection

Answer 45

Sacrificial protection is a corrosion protection method in which a more electrochemically active metal is electrically attached to a less active metal. The highly active metal donates electrons to replace those which may have been lost during oxidation of the protected metal.

Question 46

Where respiration occurs in animals and plants?

Answer 46

Animals obtain glucose for respiration by digesting food that they eat.
Plants obtain glucose for respiration by producing it through a process known as photosynthesis.
Respiration mostly occurs in the presence of oxygen, where it is called aerobic respiration.
It can also occur in the absence of oxygen, where it is called anaerobic respiration.
Aerobic respiration produces significantly more energy than anaerobic respiration.
Respiration takes place in cell structures called mitochondria.
Mitochondria occur in all cells; therefore respiration takes place in all organisms.

Question 47

Digestion process

Answer 47

Digestion is a chemical reaction that occurs in living things and is the process in which nutrients and energy are extracted from the food we eat.It occurs in a 6-7 metre tube called the alimentary tract or the digestive tract, which runs from the mouth to the anus where waste is expelled. Biological catalysts called enzymes assist to chemically breakdown food.

Question 48

Why is respiration a biological chemical reaction

Answer 48

Respiration is regarded as an example of a biological chemical reaction as it takes place in all living cells 24hrs a day to release energy from food. This energy is available to cells for their many activities such as : growth of cells, transport of substances into and out of cells heat

Question 49

Define carbonate
Define anion
Define cation
Define salt

Answer 49

An ion consisting of one carbon and three oxygen atoms or a compound that contains this species as its anion
a negatively charged ion
a positively charged ion
any chemical compound formed from the reaction of an acid with a base, with all or part of the hydrogen of the acid replaced by a metal or othercation

Question 50

Digestion process

Answer 50

Mechanical digestion is a purely physical process that does not change the chemical nature of the food. Instead, it makes the food smaller to increase both surface area and mobility. It includes mastication, or chewing, as well as tongue movements that help break food into smaller bits and mix food with saliva. The mechanical churning of food in the stomach serves to further break it apart and expose more of its surface area to digestive juices, creating an acidic “soup” called chyme. Segmentation, which occurs mainly in the small intestine, consists of localized contractions of circular muscle of the muscularis layer of the alimentary canal. These contractions isolate small sections of the intestine, moving their contents back and forth while continuously subdividing, breaking up, and mixing the contents. By moving food back and forth in the intestinal lumen, segmentation mixes food with digestive juices and facilitates absorption.

In chemical digestion, starting in the mouth, digestive secretions break down complex food molecules into their chemical building blocks (for example, proteins into separate amino acids). These secretions vary in composition, but typically contain water, various enzymes, acids, and salts. The process is completed in the small intestine.

Question 51

How does mitochondria produce energy?

Answer 51

Mitochondria, using oxygen available within the cell convert chemical energy from food in the cell to energy in a form usable to the host cell. The process is called oxidative phosphorylation and it happens inside mitochondria.