Chem4.1- Flashcards
1
Q
Chemical reaction
A
a change in which the atoms rearrange and join together to make new substance
2
Q
By the end of the reaction, what do you see probably —-.
A
looks different to what you started with
3
Q
5 characteristics of chemical reactions
A
Most chemical reactions are not easily reversible.
At the end of each chemical reaction, it’s difficult to get back to the starting substances.
All chemical reactions transfer energy to or from the surroundings.
In a chemical reaction atoms rearrange together differently.
Chemical reactions make new substances.
4
Q
2 physical reaction exmaples
A
dissolving/changing state
5
Q
4 observations you might make in a chemical reaction
A
- See huge flames or tiny sparks.
- Smell a sweet smell or a foul stink.
- Feel the substances get hotter or colder.
- Hear a loud bang or a gentle fizzing （produce bubbles of gas and a hissing sound).
6
Q
In a chemical reaction:
* The starting substances are -. (ex.—)
* The substances that are made are -. (ex.—)
The reactants and product have –.
A
reactants; products
shiny magnesium metal and oxygen
magnesium oxide (white ash)
different properties
7
Q
A hazard symbol shows —. Hazard symbols are the same everywhere.
A
how a substance can cause harm
8
Q
The burning magnesium’s flame is bright white, and looking at it —.
Raj reduces the risk from this hazard by —–.
A
directly can damage eyesight; looking at the flame through a narrow gap between his fingers
9
Q
Raj’s teacher reduces the risk from the flammable hazard by —.
A
keeping the roll of magnesium away from flames
10
Q
The reactants and products of a chemical reaction —.
A
Have different properties
11
Q
magnesium+hydrochloric acid
A
hydrogen gas (bubbles through the liquid) & magnesium chloride
12
Q
Sodium hydroxide+copper sulfate
A
Sodium sulfate & copper hydroxide
13
Q
magnesium+iron oxide
A
magnesium oxide & iron
14
Q
In the rocket flame, — react together to produce -.
A
hydrogen and oxygen; water
15
Q
There are — before and after a chemical reaction.
The numbers of atoms of each element — in a chemical reaction (=— ).
In any chemical reaction, the total mass of products is —-.
A
the same number of atoms; do not change; the mass does not change; equal to the total mass of the reactants
16
Q
hydrogen fuels—
A
rockets, cars, and buses
17
Q
- buses make waste substances that harm health and – (=greenhouse gas).
It makes the —, which causes –.
A
Diesel; carbon dioxide; Earth’s surface hotter; climate change
18
Q
Using hydrogen instead of diesel to fuel buses could —–. This might have a positive impact on the environment.
A
reduce the amounts of harmful substances and greenhouse gases
19
Q
2 shortcomings of hydrogen fuel
A
- Hydrogen is difficult to store.
- There are few hydrogen filling stations.
20
Q
Oxygen has –.
A
its own mass
21
Q
Zac wishes to test whether iron wool will react with oxygen to make the compound -.
If the mass of product is greater than the mass of iron, this will be—–.
A
iron oxide; evidence that iron reacts with oxygen from the air
22
Q
If Zac heats iron in the air, iron atoms and oxygen atoms —. The mass of iron oxide Zac makes will be — of iron Zac starts with.
A
will join together; greater than the mass
23
Q
2 Hazards of burning iron wool and 3 ways to work safely.
A
iron wool can cut skin and catch fire easily.
Wear gloves, store spare iron wool in a jar with a lid, and wear eye protection.
24
Q
3 main points of the conclusion of burning iron wool
A
- The iron atoms joined with oxygen atoms 2. they form one compound: iron oxide
- The mass of the iron oxide was greater than the mass of the iron at the start
25
When planning an investigation... (5)
1. make a hypothesis and prediction
2. choose equipments
3. work safely
4. make a conclusion
5. suggest improvements
26
5 hazard symbols
Flammable（burns easily）
Helps other substances to burn
A health hazard
Corrosive (burns skin and eyes)
Dangerous to the environment (damages things that live in water)
27
2 types of chemical reaction
combustion reaction & precipitation reaction
28
combustion reaction (2 ex.)
substance reacts quickly with oxygen
gives out heat and light
ex. magnesium with air; iron wool with air
29
precipitation reaction
A reaction where two solutions react to make a precipitate. ;
forms when 1 product is insoluble
30
In all types of chemical reactions, atoms ---to make new substances.
are rearranged and joined together differently
31
precipitate
a suspension of tiny solid particles that in a liquid / solution
32
The reactants and products in a precipitation reaction have ----: - and -.
different chemical and physical properties; color; solubility
33
soluble, insoluble
can dissolve in the solvent; cannot dissolve in the solvent
34
You can use precipitation reactions to ---.
help identify substances
35
Precipitation reactions:
potassium iodide + lead nitrate
cobalt sulfate + sodium hydrogencarbonate
copper chloride + sodium hydroxide
Yellow-lead iodide; potassium nitrate
Pink-cobalt carbonate
Blue-copper hydroxide; sodium chloride
36
Different metal compounds make ---.
blue, dark green/ brown, light green
precipitates of different colours
copper; iron; nickel
37
Chemical reactions that are useful
Combustion: release energy to cook food
precipitation: help to identify substances
others: make medicines and fertilisers
Keep living things living
38
- is formed in a corrosion reaction. Corrosion of iron=-.
Rust; rusting
39
Corrosion reaction
A chemical reaction that happens slowly on the surface a metal. May damage metal objects.
40
When iron rusts, it reacts with ---. They come from:----. Rusting happens slowly, over weeks and months.
The product of the rusting reaction is ---. This is ----.
oxygen and water; The oxygen comes from the air. The water may be in the air as gas or in its liquid state.
hydrated iron oxide; iron oxide with water loosely joined to it
41
The rust forms on --. It is ---. It easily ---. This leaves more iron exposed and ready to rust.
the surface of the iron; soft and crumbly (flaky and brown); comes off the surface of the metal
42
Corrode speed:
Magnesium Iron Gold
quickly
slowly
Do not
43
The chemical properties ----, such as ----.
of a substance describe its chemical reactions; whether it burns, corrodes, or reacts to make a precipitate
44
Most metal things we use are made from-. It is --.
steel; mainly iron
45
Two ways to prevent corrosion + their examples
1. Stops air and water touching the surface (paint, oil/grease, metal that does not easily corrode (zinc))
2. Does not react with oxygen and water at all (stainless steel that does not react with oxygen and water)
46
Every alloy has --- that are different to the elements that are mixed to make it.
Some alloys also have different -- to their elements
physical properties; chemical properties
47
Stainless steel is ---. It has --- to the elements that are mixed to make it. It does not -.
an alloy of iron; different chemical properties; rust
48
For 2 hydrogen and 2 chlorine atoms combining to form hydrogen chloride (4 atoms):
Why the total mass of reactants is equal to the total mass of the product in the reaction?
There are two chlorine atoms and two hydrogen atoms in both the reactants and the product. Since the number of atoms does not change, the mass also does not change.
49
acids (3) alkaline (3) neutral (1)
lemon, limes, vomit; toothpaste, baking soda, soap; pure water
50
Neutral
a solution is neutral when its pH is 7 (ex. pure water); Not acidic or alkaline
51
acidity
a chemical property that describes how acidic a substance is
52
alkalinity
a chemical property that describes how alkaline a substance is
53
indicator
a solution of a dye that changes colour in acidic and alkaline solutions
54
Plant indicators (4)
litmus (dye obtained from lichen), red cabbage, hibiscus flower, beetroot
55
Plant indicators' colours in acidic & alkaline solutions:
litmus:
red cabbage:
hibiscus flower:
beetroot
red; blue
red; yellow/ green/ blue
dark pink/ red; dark green
red/ purple; yellow
56
Paper is soaked in litmus to make --. Blue litmus paper turns ---. Red litmus paper turns ---.
litmus paper; red in acid; blue in an alkaline solution
57
6 apparatus used in a science lab to make an indicator
beaker, test tube, Bunsen burner, filter funnel, filter paper, conical flask
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Indicators show----.
whether a substance is acidic or alkaline
59
Some acidic substances are ---, but others are - (ex. -).
good to eat or drink; corrosive; hydrochloric acid
60
The pH scale shows ----.
how acidic or alkaline a solution is, or whether it is neutral
61
The lower the pH, the---.
The higher the pH, the ---.
more acidic the solution; more alkaline the solution,
62
A neutral solution has---.
a pH of 7.0
63
Secondary data
Evidence/ data that has been collected by someone else.
64
8 examples of acidic solutions and alkaline solutions
Acidic: black coffee; milk; orange juice; sulfuric acid; vinegar
Alkaline: blood, sodium hydroxide, drain cleaner
65
You can use litmus paper to find out --.You cannot use it to --.
whether a solution is acidic or alkaline; measure pH
66
You can use the universal indicator to find out --.
the pH of a solution
67
Universal indicator is -----.
a mixture of a dye that changes color to show how acidic or alkaline a substance is
68
Jabir Ibn Hayyan discovered how to make --.
sulfuric acid
69
Sulfuric acid is used to make
fertilisers, insecticides to help grow food crops; detergents, dyes, medicines, paints, and batteries.
70
An acidic solution has a pH -- and an alkaline solution has a pH --.
less than 7; greater than 7
71
pH is measured with ---.
universal indicator or a pH probe
72
1 example of neutralisation reaction that cause a fizzing
citric acid (in lemon juice) + sodium hydrogencarbonate (baking soda)= (one of the products) carbon dioxide (that makes bubbles)
73
Neutralisation
a type of chemical reaction in which an alkaline reacts with an acid and the the pH gets closer to 7.
74
To find the volume of alkali (sodium hydroxide) that neutralises the acid (hydrochloric acid)
1. Add the universal indicator to the acid.
2. Add sodium hydroxide to the acid-indicator mixture.
3. Continue to add the alkali to the mixture until its colour is green.
75
Some soils --- than others. Every plant has its ---.
are more acidic or alkaline; preferred soil pH
76
2 usage of neutralisation reactions
change soil pH & treat stomach ache
77
Why choose a measuring cylinder over a beaker to measure volumes?
A measuring cylinder can show smaller differences in volume, therefore the volume can be measured more precisely.
78
An investigation can involve-----.
considering variables, choosing equipment, collecting evidence, making a conclusion and making improvements
79
5 causes of acidic gases
exhaust gases from cars and lorries filled with petrol and diesel; waste acidic gases from factories; burning rubbish; acidic gases produced by power stations burning coal
80
How is acid rain produced?
The acidic gases mix with the air. They dissolve in rain, making it acidic
81
The chemical reaction of acid rain with solid white marble
Nitric acid reacts with calcium carbonate to make
calcium nitrate, water, carbon dioxide
82
5 actions to help solve the problem of acid rain
Factories can neutralise their acidic waste.
Use cleaner methods to produce electricity (wind turbines & solar cells)
People can drive electric or hydrogen cars or walk or cycle
Power stations can neutralise/remove their acidic waste
Add alkaline substance to acidic lake
83
Acid rain problems
kills trees
damages buildings
makes lakes acidic (some plants and animals cannot live in them)
84
Some indigestion tablets contain --. When you add --- there is a - reaction. One of the products is --. The other two are ---.
calcium carbonate; calcium carbonate to hydrochloric acid; neutralisation; carbon dioxide; water and calcium chloride
85
Test for CO2 gas
1. Bubble the gas through limewater solution
2. If the limewater solution turns milky/ cloudy, CO2 is present
86
Some -- react with acids. For example:- and -
The products are --
Metal elements; magnesium; hydrochloric acid; magnesium chloride and hydrogen.
87
How to test for hydrogen gas
Collect the gas using an empty test tube
light a split
place splint in the gas test tube
flame goes out with a squeaky pop
88
How to test for oxygen gas
Collect the gas using an empty test tube
light a split and blew it out
place the glowing splint in the gas test tube
splint relights
89
Acids react with carbonate to make -
Acids react with some metals to make -
Carbon dioxide makes --
Hydrogen puts out ---
Oxygen -- splint
carbon dioxide gas; hydrogen gas; limewater milky; a lighted splint with a squeaky pop; relights a glowing
90
What is a model
an idea that explains observations and helps in making predictions
91
3 observations made that cause people to reject the flat Earth model
1. Ships appeared to sink as they go over the horizon
2. the shadow of the Earth on the Moon is round
3. Observations from space
92
Modern model of the structure of the Earth (4 layers)
* A solid crust, made of different types of rock. The crust does not
flow.
* The mantle, which is solid but flows slowly.
* The liquid outer core, which is mainly iron and nickel.
* The solid inner core, also mainly iron and nickel.
93
Evidences that let us know about the Earth's structure
from rocks, earthquakes, mines
94
Evidence from rocks: Scientists studied rocks ---
on the surface of the Earth, brought to the surface by volcanoes, under oceans
95
Evidence from earthquakes (2)
1909: studies shock wave patterns at different places
Shock waves had come through two different layers. Found the crust and the mantle.
1930: studies shock wave patterns and could not explain them using the model of the time (Earth's core is the same all the way through)
core has two parts. found the solid inner core
96
Evidence from mines
Temperatures increase from crust to core. The core may be hotter than the surface of the Sun.
97
What is the model of plate tectonics?
The model that suggests that the Earth's crust and uppermost mantle are made of about 12 slabs of solid rock (explains earthquakes, volcanoes, and the formation of some mountains) called the tectonic plates
98
Alfred Wegener's two piece of evidence
E1: There are similar rocks at the edges of the continents, where they might have been joined.
E2: There are fossils of the same reptile in Africa and South America. It could not have swam across the ocean because it lives in shallow water
98
Alfred Wegener's hypothesis (he was a person who mainly studied the weather not rocks)
Africa and South America were once a single piece of land. The land broke up and the pieces drifted apart, making continents.
99
How do the - plates move?
The lower mantle is ----. The heat makes ---, even though it is -. The --- move with the -- below. Their speed is --- per year.
tectonic; heated from deep inside the Earth; the lower mental flow; solid; solid tectonic plates; flowing mantle; a few centimeters
100
A tectonic plate is one of about --- on the Earth's surface. It is made of - and on --.
12 huge slabs of rock; crust; top of the mantle
101
The tectonic plates -- and -- with the --.
rest on; move; lower mantle
102
Which reptile's fossils were found in both Africa and South America?
Mesosaurus
103
Who claimed that Africa and South America were once a single piece of land?
Alfred Wegener
104
Most scientists do not work in isolation. They --- before them. They ---.
build on the work of scientists; collaborate with others, both nearby and far away
105
4 ways scientists share and discuss their evidence and ideas
1. Give talks at conferences and webinars
2. talking to and messaging each other
3. Show posters at conferences
4. Write papers for scientific journals
106
Earthquakes happen when ---.
tectonic plates move against each other suddenly
107
How does an earthquake happen?
Because of friction, the plates cannot slide smoothly. Sometimes they get stuck. Huge forces build up. Eventually, the two plates overcome the frictional forces. The plates slip suddenly.
108
The place where the --- of an earthquake. Shock waves ---. The shock waves make buildings collapse.
plates slip is the focus; spread from there
109
Earthquakes are common at ---.
moving plate boundaries
110
2 clues that an earthquake may happen soon
1. More/ bigger vibrations in the Earth's crust （seismometers picked them up)
2. Large amounts of radon gas suddenly escape from cracks in the crust
111
How did the Himalayas form?
The India plate moved north and the Eurasian plate moved south. When they collided, the edges of the continents crumpled together and piled up.
112
- mountains may form when --.
Fold; tectonic plates push together
113
8 of the tectonic plates
Nazca plate, South American plate, North American plate, Pacific plate, Eurasian plate, African plate, Australian plate, Antarctic plate
