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PPT_Cambridge 7th Grade-5

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16 views49 pages

PPT_Cambridge 7th Grade-5

Uploaded by

Najva Amin
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PPTX, PDF, TXT or read online on Scribd
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Glossary

• Material: a substance or
mixture of substances
that make up an object.
• Structure: form; shape
CHAPTER 2:
Materials and their structures
2.1 Solids, liquids, and gases
Key Words part 1
◦ Compressed: squeezed into a smaller
space ◦ Particles: very small pieces of matter
that everything is made up of
◦ Flow: (of a liquid or gas) to move
smoothly, to pour ◦ Pour: (of a liquid or gas) to move
smoothly, to flow
◦ Hypothesis: a suggestion for an
explanation

◦ Matter: everything that has mass and


takes up space
Key Words part 2
◦ Property: The features (qualities) of a nothing, no particles at all
material and how it behaves

◦ Vibrate: to move backwards and


◦ States of matter: all matter is either forwards repeatedly
solid, liquid, or gas

◦ Volume: the amount of space taken up


◦ Theory (plural theories): an idea to by a solid, liquid, or gas
explain evidence (anything that helps to
prove that something is or is not true)

◦ Vacuum: an area where there is


Getting started
Hint
Looking at states of matter
◦ Solids
◦ Liquids
◦ Gases

These states of matter have different behaviors, the ways they behave are called
properties.
Solids
1. Keep the same shape.
2. Take up the same amount of space. (Its
volume remains constant regardless of its
container or shape.)
3. Keep the same volume.
4. Cannot be compressed (squashed) or poured.

Glossary

• Take up: use; occupy


• Squashed: squeezed
with force
Liquids
1. Take the shape of the container they are
in.
2. Can be poured.
3. Cannot be compressed.
4. Take up the same amount of space,
whatever shape the container.
5. The volume of a liquid doesn’t change.
Gases
1. Flow like liquids. (can be poured)
2. They will fill any closed container
they are in.
3. Are very easy to compress.
4. Their volume can change.
5. They weigh very little.
6. You cannot see or feel them, but you
can sometimes smell them, and feel
air moving on your face.
◦ Liquids cannot be compressed but gases are easy to compress.
Glossary

• Definite: clearly
Properties of states of matterdefined; exact;
fixed;
English Language Skills Workbook 7
Singular and plural verbs
◦ Verb: a word that describes an action or state.

◦ The verb to be:


◦ The verb is can be used with singular things, e.g. There is a beaker.
◦ The verb are can be used with plural things, e.g. There are many organs in the human
body.

◦ For other verbs, they have to agree with the person or objects you are talking about:
◦ For it, she, or he, you must put an –s or –es at the end of the verb.

◦ Note:
- For most verbs, we add -s to the base form, e.g. walk- walks
- When the verb ends in -ch, -ss, -sh, -x or -zz, we add –es, e.g. wash- washes
- When the verb ends in a consonant + -y we change y to i and add –es, e.g. study-
studies
- when the verb ends in a vowel + -y we add –s, e.g. enjoy- enjoys

◦ Note:
- The verb can be followed by a singular or plural noun, e.g.
 He discovers a solution.
 He discovers solutions.
Summary
Scientists look at what matter
does
◦ Some explanations of scientists about the matter behaviors:

1. You can smell food cooking in another room.


2. Some substances get bigger when you heat them.
3. Liquids, such as water, change to a gas when you heat them.
4. Substances change from liquid to solid when you cool them.

◦ When scientists form an hypothesis?


- When they try to come up with ideas to explain why these things happen.
◦ What is hypothesis?
- A suggestion for an explanation.
◦Theory: when an hypothesis has been tested and widely accepted as
valid by other scientists.

◦ The idea of particles can be the best theory to explain how matter
behaves.

◦ Particles definition: Tiny parts of matter.

◦ The theory says that particles are arranged differently for different states of
matter.
Particle Theory
◦Solids:
1. Particles are arranged in a fixed pattern.
2. Are held together strongly and tightly.
3. They can vibrate (make small movements)
but in the same place.
◦ Liquids:

1. The particles touch each other.


2. Are held together weakly.
3. Can move past one another and touch each
other.
4. Liquids can change shape.
◦ Gases:

1. The particles do not touch each other.


2. They are a long way apart.
3. They can spread out by themselves to fill up the
space.
4. Gases can change shape.
Explain the properties
Note:
1. If the particles can move past one another, matter can be poured.
2. If the particles in the matter spread out or move closer, the matter can change its volume.

Solids:
The particles in a solid are very close together, for this
reason, it’s difficult for the volume of a solid to get smaller.

 Why do solids have a fixed shape?


Because attractive forces hold the particles together and
stop particles from moving around.

Note:
Solid cannot flow because the particles can only vibrate.
◦ Liquids:

The volume of a liquid cannot be changed. The


particles cannot be compressed because they
are very close together and can touch each
other.

 why don’t liquids have a fixed shape?


Because the attractive forces between the
particles are weak enough to allow them to
move and flow but strong enough to hold them
together.
◦ Gases:

The particles in a gas can move quickly and easily


because no attractive forces exist between them so
gas has no fixed shape or volume.

 What will happen when you compress a gas?


The particles move closer together and the gas
takes up less space.
Powder:
◦ Each speck (grain) of powder is a solid and it’s so
small that it can flow and be poured.
◦ They are in the form of small solid grains. These
maintain their shape, but there are space between
them so the grains (specks) can move past one
another same as liquids.
◦ There is air in the spaces between the grains of
powders, and when the grains are pushed together
the air is forced out, that’s why the grains can be
squeezed into a smaller space.
Questions
2.2 Changes of state
Key Words
(熔 ( 蒸汽 )
化 ) )
( 熔点
(缩
( 水蒸气 ) 合)

( 蒸发 ) ( 状态变化 )

( 沸点 )

( 温度计 ) ( 半月板 )
Question?????

◦Give me five facts about solids, liquids, and


gases.
Changing State
◦ Melting: change of a solid into a liquid when heat is applied, e.g. ice in a warm place.

◦ Melting point: the point (temperature) at which materials change from a solid to a
liquid.

◦ Water Vapour: water in the gaseous ( 气态的 ) state that exists below its boiling point.
This process is called evaporation.

◦ If you heat water until its temperature reaches 100°C, it will boil.

◦ Steam: is water heated to the point that it turns into gas. 100°C is the boiling point of
water.
◦ Condensation: the change of the state of matter from the gas phase into the
liquid phase.

◦ Freezes: Freezing is the process when a liquid turns into a solid, e.g. if you put
liquid water in the freezer it becomes ice.

◦ Changes of state: a physical change in a matter


Measuring Volume
◦ A measuring cylinder can be used to
measure the volume of a liquid.

◦ How to measure the volume of a


liquid in a measuring cylinder?
 measure from the bottom of the
meniscus, so your eye must be at the
level with the meniscus.
Measuring temperature
◦ A thermometer can be used to measure the temperature.

◦ How does a thermometer work?


 When there is an increase in heat, the liquid inside the thermometer expands, so it
rises up inside it.

◦ Note:
When you read the temperature from the scale your eye must be in the level with the
top of the liquid.
Question 1
Question 2
Measuring the temperature when you
heat water experiment
2.3 Explaining Changes of State
Key Words

热能

转移

扩张
吸引力
Changes of state
◦ Heating Solids:
When solids are heated they get bigger
(expand), and heat energy is transferred
to the particles. The more energy they
get, the more they vibrate, so they take
up more space.

Attractive forces let the particles keep


their position.
◦ Melting solids:
Solids become liquid when they are heated more strongly, and they melt.

◦ How do they melt?


The particles vibrate so much that attractive forces between them are not strong
enough to keep their shape. They can now move and past one another.

Note:
The forces are still strong enough for the particles to stay in touch with one another.
Boiling Liquids
When liquids are heated
◦ The particles in liquids touch each other.
◦ The particles are held together weakly.
◦ The particles move more as heat energy is
transferred to them.

Some particles can move and escape as gas


particles because they have enough energy to
break the weak attractive forces.
Colling gases

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