Hi Flashcards

1
Q

What is a chemical change?

A

Formation of a new substance

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2
Q

What is effervescence

A

When a chemical reaction fizzes

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3
Q

What is carbon dioxide gas?

A

Lumps of chalk are reacting with hydrochloric acid

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4
Q

What is precipitation?

A

Some reactions between solutions produce a solid

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5
Q

What is precipitate?

A

The solid formed in precipitation reaction.

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6
Q

What is exothermic reaction?

A

Reactions that give out heat

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7
Q

What is combustion?

A

The process of burning sth

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8
Q

What is an endothermic reaction?

A

Any chemical reaction that absorbs heat from its environment

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9
Q

What is an reactant in a chemical reaction?

A

The substance we start with in a chemical reaction are called reactants

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10
Q

What is the product?

A

The new substance formed in a chemical reaction

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11
Q

Why are word equations useful in a chemical reaction?

A

Word equations are a useful way of describing chemical reactions.

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12
Q

What is a physical change?

A

Physical changes are different from chemical changes in that no new substance are formed during the change

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13
Q

What are mixing substances?

A

Mixing substances can be described as a physical change. If no new substances are produced it is usually quite easy to separate the substances in a mixture.

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14
Q

What are the mixtures in air?

A

A mixture of gases including oxygen, nitrogen, argon and carbon dioxide

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15
Q

What are the mixtures in sea water?

A

A mixture of water , salt and other dissolved substances

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16
Q

What are the mixtures in soil?

A

A mixture of rock fragments ,water,dissolved minerals, air and humus

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17
Q

What are the mixtures in rocks

A

A mixture of different minerals

18
Q

What are the changes of state?

A

Melting,boiling,evaporation,condensation and freezing.

19
Q

What is matter?

A

Matter is the scientific word used to describe all the different types of substances and materials found in our universe.

20
Q

What is the particles theory?

A

All matter is composed of tiny indivisible particles too small to see

21
Q

What is a atom?

A

The simplest particle

22
Q

What is the diameter of the largest atom?

A

0.00 000 000 5.

23
Q

What are molecules?

A

Two or more atoms joined together

24
Q

How do you change a state

A

Heating/cooling

25
Q

What happens to the particles when a substance is heated?

A

When a substance is heated the particles have more energy and move faster so the temperature rises.

26
Q

What happens to the particles when a substance is cooled?

A

When a substance is cooled the particles have less energy and move slower so the temperature falls

27
Q

What is melting?

A

When the particles vibrate fast enough to break free from each other

28
Q

What is evaporation?

A

When the particles at the surface of the liquid vibrate fast enough to escape and form

29
Q

What is boiling?

A

The process by which a liquid turns into a Vapor when it is heated to its boiling point.

30
Q

What is condensation?

A

The process by which water Vapor in the air is changed into liquid water.

31
Q

What is freezing?

A

When a liquid is cooled,heat energy is removed from the particles making them move more slowly.If the cooling is continued long enough the particles will eventually not be able to move about this is called freezing and a solid is formed

32
Q

What is sublimation?

A

(Gas to Solid) the conversion between the solid and the gaseous phases of matter, with no intermediate liquid stage.

33
Q

What is diffusion?

A

Diffusion occurs when the particles of one substance spread out and mix with the particles of another substance

34
Q

What is expansion?

A

When a substance gets bigger and takes up more space

35
Q

What is contraction?

A

When a substance gets smaller and takes up less space

36
Q

What is density?

A

Mass per unit volume

37
Q

What is air pressure

A

The force exerted on a surface by the air above it is gravity pulls it to earth

38
Q

How can we measure air pressure?

A

By using a barometer

39
Q

What is the unit of measuring air pressure?

A

Pascals

40
Q

What does a vacuum pump do?

A

A vacuum pump can be used to remove the air from inside a container